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IRIS Performer™ Programmer`s Guide

1. CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE 1 i A r an AUW a alloc 24 sizeof ushort arena front left Jx pack 381 Chapter 10 libpr Basics 382 vindex vindex vindex vindex vindex vindex norms pfVe pfSetVec3 nor pfSetVec3 nor pfSetVec3 nor pfSetVec3 nor pfSetVec3 nor pfSetVec3 nor nindex nindex 0 0 nindex 1 nindex 3 4 nindex 4 tcoords pfVec2 pfSetVec2 tcoords 0 0 0f pfSetVec2 tcoords 1 1 0f pfSetVec2 tcoords 2 1 0f pfSetVec2 tcoords 3 0 0f tindex ush tindex 0 0 tindex 1 tindex 2 2 tindex 3 tindex 4 0 tindex 5 tindex 6 2 tindex 7 tindex 8 0 tindex 9 tindex 10 2 tindex 11 tindex 12 0 tindex 13 tindex 14 2 tindex 15 tindex 16 0 tindex 17 tindex 18 2 tindex 19 tindex 20 0 tindex 21 tindex 22 2 tindex 23 Allocate the o oN Aonwatk c3 ms ms ms ms ms ms vindex vindex vindex vindex jo tight i top i bottom PoeANN WwW pfMalloc 6 sizeof pfVec3 arena 0 0O 0 LT 0 0 2 0 0 f Sly 0 Oty 4 1 0 Dp HL 0 0 00f 1 0f Os 0 7 Le UEN Ls Qf 050 3 1 0870 008 3 0 0f 0 0f 0 Of 0 0f ushort pfMal
2. return gset 383 Chapter 10 libpr Basics Managing Nongraphic System Tasks 384 This section describes routines that manage nongraphic tasks such as clocks memory I O and error handling Clocks IRIS Performer provides clock support for timing operations High Resolution Clock IRIS Performer provides access to a high resolution clock that reports elapsed time in seconds To start a clock call pfInitClock with the initial time in seconds usually 0 0 as the parameter Subsequent calls to pfInitClock reset the time to whatever value you specify To read the time call pfGetTime This function returns a double precision floating point number representing the seconds elapsed from initialization added to the latest reset value The resolution of the clock depends on your system type and configuration In most cases the resolved time interval is under a microsecond and so is much less than the time required to process the pfGetTime call itself Exceptions are older Power Series machines with IO2 boards and some Personal Iris computers You can use the IRIX hinv command to see whether your Power Series system has an IO2 board or an IO3 board installed Onyx Crimson Indigo Indigo and Indy systems all provide submicrosecond resolution On a machine that uses a fast hardware counter the first invocation of pfInitClock forks off a process that periodically wakes up and checks the
3. IEWING_MODE OTW THERMAL BOTH CLUDE_INACTIVE_POLYGONS EL FILTER lt filter_regexp gt TX_NORMALS EAF_SIZE_MAX lt integer_size gt Zz oe iw HPSERHS COND Project selection The minimum control file specifies which project to load The default is to load the entire project The assembly prefix is assumed to be the same as the project name unless the user has specified a different assembly prefix The control file also allows the user to specify the S1K project directory If the project directory is specified in the control file then this setting overrides the environment variable setting SIKPROJ if any The user may load a portion of the entire S1000 data base by specifying the coordinates of a search 301 Chapter 9 Importing Databases 302 window see the S1000 API User s Manual for details about search window selection Coordinate system specification The database load occurs in either assembly ASSY coordinates or UTM The S1000 data base origin the ASSY origin is at the southwest corner of the assembly If UTM coordinates are selected then the search window is assumed to be given in UTM coordinates and the output will be in UTM coordinates The user may however establish his own local reference frame by specifying an origin for the output database Again if UTM is specified the origin is assumed to be given in UTM otherwise ASSY The S1000 API pro
4. pfGSetGState gset gst return Geet 380 libpr Sample Code Example 10 13 demonstrates construction of a textured cube This example can be found in the file usr share Performer src pguide libpr C texcube c Example 10 13 Constructing a Textured Cube With libpr texcube croutine for constructing a textured cube geoset AS include lt Performer pr h gt E1 0 define CUBE_SIZ pfGeoSet f MakeTexCube void arena pfGeoSet g set pfGeoState gst pfTexture pfTexEnv t pfVec3 ver tex env ts norms pfVec2 tcoords ushort vin dex nindex tindex Data arrays to be passed to pfGSetAttr should be allocated from heap memory verts pfVec3 pfSetVec3 verts 0 CUBE_SIZ pfSetVec3 verts 1 CUBE_SIZ pfSetVec3 verts 2 CUBE_SIZ pfSetVec3 verts 3 CUBE_SIZ pfSetVec3 verts 4 CUBE_SIZ pfSetVec3 verts 5 CUBE_SIZ pfSetVec3 verts 6 CUBE_SIZ pfSetVec3 verts 7 CUBE_SIZ vindex ushort pf vindex 0 0 vindex 1 vindex 2 2 vindex 3 vindex 4 0 vindex 5 vindex 6 7 vindex 7 vindex 8 4 vindex 9 vindex 10 6 vindex 11 pfMalloc 8 sizeof pfVec3 arena Ys CUBE_SIZE UBE_SIZ Q CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE CUBE_SIZE
5. pfSeqMode smoke_seq PFSEQ START pfSwitchVal s 3 else pfSwitchVal s PFSWITCH_OFF pfLOD Nodes A pfLOD is a level of detail node Level of detail switching is an advanced concept that is discussed in Chapter 7 Frame and Load Control A level of detail node specifies how its children are to be displayed based on the visual range from the channel s viewpoint Each child has a defined range and the entire pfLOD has a defined center Table 5 5 describes the functions for working with pfLODs Table 5 5 pfLOD Functions Function Description pfNewLOD Create a level of detail node pfLODRange Set a range at which to use a specified child node pfGetLODRange Find out the range for a given node pfLODCenter Set the pfLOD center pfGetLODCenter Retrieve the pfLOD center Node Types Table 5 5 continued pfLOD Functions Function Description pfLODTransition Set the width of a specified transition pfGetLODTransition Get the width of a specified transition pfLayer Nodes A pfLayer is a leaf node that resolves the visual priority of coplanar geometry A pfLayer allows the application to define a set of base geometry and a set of layer geometry sometimes called decal geometry The base geometry and the decal geometry should be coplanar and the decal geometry must lie within the extent of the base polygons Table 5 6 describes the functions for working with pfLayers Table
6. Use pfChanShare to set the share mask for a channel group By default channels share all attributes except PRCHAN_VIEW_OFFSETS When you add a pfChannel to a channel group it inherits the share mask of that group A change to any shared attribute is applied to all channels in a group For example if you change the viewpoint of a pfChannel that shares PFCHAN_VIEW with its group all other pfChannels in the group will acquire the same viewpoint Two attributes are particularly important to share in adjacent display multiple channel simulations PRCHAN_SWAPBUFFERS and PFCHAN_LOD PFCHAN_LOD ensures that geometry that straddles displays is drawn the same way in each channel In this case all channels will use the same LOD modifier when rendering their scenes so that LOD behavior is consistent across channels PRCHAN_SWAPBUFFERS ensures that channels refresh the display with a new frame at the same time pfChannels in different pfPipes that share PRCHAN_SWAPBUFFERS will frame lock the pipelines together Using Channels Example 4 9 illustrates the use of multiple channels and channel sharing Example 4 9 Channel Sharing pfChannel Chan MAX_CHANS main pfiInit Set number of pfPipes desired THIS MUST BE DONE BEFORE CALLING pfConfig x pfMultipipe NumPipes pfConfig 0 Tnitscenetji InitChannels pfFrame Application main loop while SimDone v
7. Sinusoidally modify morph weights to oscillate between cube and sphere xy static void breatheMorph pfMorph morph double t float s sinf t 1 0 2 0 float weights 2 weights 0 s weights 1 1 0f s pfMorphWeights morph 0 weights coordinate weights pfMorphWeights morph 1 weights normal weights 245 Chapter 8 Creating Visual Effects static pfMorph initMorph void pfGeoSet gset pfGeode geode pfGeoState gstate pfMaterial emt pfMorph morph ushort icoords inorms pfVec3 coords ncoords norms nnorms float teres 2 3 int i nSph void xarena pfGetSharedArena morph pfNewMorph geode pfNewGeode gset pfdNewSphere 400 arena gstate pfNewGState arena mtl pfNewMtl arena pfMtlColor mtl PFMTL_DIFFUSE 1 0f 0 0f 0 0f pfMtlColor mtl PFMTL_SPECULAR 1 0f 1 0f 1 0f pfMtlColorMode mtl PFMTL_BOTH PFMTL_CMODE_OFF pfMtlShininess mtl 32 pfGStateAttr gstate PFSTATE_FRONTMTL mtl pfGStateMode gstate PFSTATE_ENLIGHTING 1 pfGSetGState gset gstate T pfAddGSet geode gset pfAddChild morph geode NULL forces recomputation of bound Force it to be static to avoid expensive recomputation Static bound should encompass the extent of all morph possibilities pfGSetBBox gset NULL PFBOUND_STATIC p
8. pr_ or nb_ are internal functions and should not be used by applications There are three main types of C classes in IRIS Performer The following description is based on this categorization of the main types public structs libpr classes and libpf classes A fourth distinct class is pfType the class used to represent the type of libpr and libpf classes Public Structs These classes are public structs with exposed data members They include pfVec2 pfVec3 pfVec4 pfMatrix pfQuat pfSeg pfSphere pfBox pfCylinder and pfSegSet libpr Classes These classes derive from pf Memory When multiprocessing all processes share the same copy of the object s data members libpf Classes These classes derive from pfUpdatable and when multiprocessing each APP CULL and ISECT process has a unique copy of the object s data members Programming Basics Programming Basics pfType Class As with the C API information about the class hierarchy is maintained with pflype objects Header Files The C include files for libpf and libpr are in usr include Performer pf and usr include Performer pr respectively An application using a class should include the corresponding header file Table 14 2 Header Files for libpf Scene Graph Node Classes libpf Class Include File pfBillboard lt Performer pf pfBillboard h gt pfDCS lt Performer pf pfDCS h gt pfGeode lt Performer pf pfGeode h gt pfGroup lt Perf
9. 148 node2 pfNewDCS pfAddChild node2 model2 pfGetNodeBSphere model2 amp sphere if sphere radius gt 0 0f pfDCSScale node2 1 0f sphere radius Create the hierarchy dcs4 pfNewDCS pfAddChild dcs4 nodel pfDCSScale dcs4 0 5f dcs3 pfNewDCS pfAddChild dcs3 nodel pfAddChild dcs3 dcs4 dcsl pfNewDCS pfAddChild dcsl node2 dcs2 pfNewDCS pfAddChild dcs2 node2 pfDCSScale dcs2 0 5f pfAddChild dcsl dcs2 scene pfNewScene pfAddChild scene dcs1 pfAddChild scene dcs3 pfAddChild scene pfNewLSource Configure and open GL window pipe pfGetPipe 0 pw pfNewPWin pipe pfPWinType pw PFPWIN_TYPE_X pfPWinName pw IRIS Performer pfPWinOriginSize pw 0 0 500 500 pfOpenPWin pw chan pfNewChan pipe pfChanScene chan scene pfSetVec3 view xyz 0 0f 0 0f 15 0f pfSetVec3 view hpr 0 0f 90 0f 0 0f pfChanView chan view xyz view hpr Loop through various transformations of the DCS s Sample Program for z 0 0f z lt 1084 z 4 0f pfDCSRot desl z lt 360 int z 360 0 0f z gt 360 amp amp z lt 720 int z 360 z gt 720 int z 360 0 0f pfSinCos z amp s amp c pEDCSTrans des2 gt 1 0f cy 1 08 Sy pfDCSRot dcs3 z 0 0 pfDCSTrans dcs3 4 0f c 4 0f s pfDCSRot dcs4 0 0 z pfDCSTrans dcs4
10. Level of Detail Management in Chapter 7 Billboard Objects Many of the objects in databases can be considered to have one or more axes of symmetry Trees for example tend to look nearly the same from all horizontal directions of view An effective approach to drawing such objects with less graphic complexity is to place a texture image of the object onto a single polygon and then rotate the polygon during simulation to face the observer These self orienting objects are commonly called billboards For information on billboards see pfBillboard Nodes in Chapter 5 Animation Sequences Animated events in simulation environments often have a sequence of stages that follow each other without variation Where this is the case you can often define this behavior in the database during database construction and allow the behavior to be implemented by the real time visual system without intervention by the application process An example of this would be illuminated traffic signals in a driving simulator database There are three mutually exclusive states of the signal one with a green lamp one with the amber and one with the red The duration of each state is known and can be recorded in the database With these intervals built into the database simulations can be performed without 23 Chapter 2 IRIS Performer Basics 24 requiring the simulation application to cycle the traffic signal from one state to the next The si
11. Nodes pfNode As discussed in Attribute Inheritance on page 112 all libpf nodes are arranged in a type hierarchy which defines the inheritance of capabilities The base node class is pfNode all other nodes inherit the attributes of a pfNode A pfNode is an abstract class meaning that a pfNode can never be explicitly created by the application Its purpose is to provide a root to the type hierarchy and to define the attributes that are common to all node types pfNode Attributes The following pfNode attributes are inherited by all other libpf node types e Node name e Parent list e Bounding geometry e Intersection and traversal masks e Callback functions and data e User data Bounding geometry intersection masks user data and callbacks are advanced topics that are discussed in Chapter 6 Database Traversal The routines that set get and otherwise manipulate these attributes can be used by all libpf node types as indicated by the keyword Node in the routine names Nodes used as arguments to pfNode routines must be cast to pfNode to match parameter prototypes as shown in this example pfNodeName pfNode dcs rotor_rotation However you usually don t need to do this casting explicitly When you use the C API and compile with the ansi flag which is the usual way to compile IRIS Performer applications libpf provides macro wrappers around pfNode routines that automatically perform argum
12. generateShellLODs get the LOD s extents pfGetNodeBSphere ViewState gt LOD amp ViewState gt bSphere pfLODCenter ViewState gt LOD ViewState gt bSphere center set ranges for LODs there should be num LODs 1 range entries setLODRanges ViewState gt LOD ViewState gt minRange ViewState gt maxRange ViewState gt max Level of Detail Transition Blending An undesirable effect called popping occurs when the sudden transition from one LOD to the next LOD is visually noticeable This distracting image artifact can be ameliorated with a slight modification to the normal LOD switching process In this modified method a transition per LOD switch is established rather than making a sudden substitution of models at the indicated switch range These transitions specify distances over which to blend between the previous and next LOD These zones are considered to be centered at the specified LOD switch distance as shown by the horizontal shaded bars of Figure 7 3 Note that Performer limits the transition distances to be equal to the shortest distance between the switch range and the two neighboring switch ranges For more information see the pfLODTransition reference page As the range from eyepoint to LOD center point transitions the blend zone each of the neighboring LOD levels is drawn by using transparency to composite samples taken from the present LOD model with samples taken from
13. pfWindow win over Initialize Performer pfiInit pfInitState NULL Initialize the window win pfNewWin NULL pfWinOriginSize win 100 100 500 500 pfWinName win Iris Performer pfWinType win PFWIN_TYPE_X pfWinMode win PFWIN_HAS OVERLAY 1 over pfNewWin NULL pfWinName over Iris Performer Overlay pfWinType over PFWIN_TYPE_X PFWIN_TYPE_OVERLAY LES if we can get the desired overlay visual if pfChooseWinFBConfig over OverlayAttrs pfNotify PFNFY_NOTICE PFNFY_PRINT pfChooseWinFBConfig failed for OVERLAY win pfOpenWin win First select and draw into the overlay window pfWinIndex win PFWIN_OVERLAY_WIN Select causes the index to be applied pfSelectWin win Then select the main gfx window pfWinIndex win PFWIN_GFX_WIN pfSelectWin win Windows Example 10 11 demonstrates the selection of X input events on a pfWindow This example is taken from usr share Performer src pguide libpr C hlcube c See the usr share Performer src pguide libpf C complex c sample program for a detailed example of using either GL or forked X input on pfWindows Example 10 11 pfWindows and X Input pfWSConnection Dsp void main void pfWindow win pfWSWindow xwin Initialize Performer pfiInit pfInitState NULL Initialize the window win pfNewWin
14. DWB 276 DXF 277 FLIGHT 280 281 GDS 282 GFO 282 IM 284 IRTP 285 LSA 287 LSB 287 MEDIT 291 NFF 292 OBJ 293 Open Inventor 285 PHD 295 POLY 273 PTU 298 S1000 300 SGF 302 SGO 303 SPF 307 SPONGE 308 STAR 308 STL 309 SV 311 TRI 314 UNC 314 VRML 285 FOV See field of view 93 fractal geometry 38 frame accurate definition 517 frames definition 517 management 191 overrun 195 rate 63 synchronization 195 free 386 537 Index free store management 46 Friends of Performer 28 frustum 93 as camera See channel as culling volume 409 definition of 518 FTP xxxv function callbacks 171 G gaze vector definition 518 GDS format See formats genlock 385 geometry 30 coplanar See coplanar geometry definition pfGeoSet 32 nodes 137 rendering state pfGeoState 33 rotating 140 465 volumes See volumes geometry movie 24 getenv 393 getting started xxv GFO format See formats gift software xxviii gldebug 467 468 GLdebug history 469 gldebug utility 468 global state 358 glprof 467 glprof utility 469 glXChooseVisual 370 GLXgetconfig 370 GLXlink 370 371 538 graph defined 518 directed acyclic 30 stage timing See stage timing graph graphical user interface 3 graphics attributes 333 load See load management modes 333 335 pipelines See pipelines state 333 state elements defini
15. The Texas Instruments S1K Loader is built on top of the S1000 Data Base API developed by Loral Advanced Distributed Simulation The S1000 API is used to access the following S1000 data base elements e 3 D polygons for terrain micro terrainand culture e Model instance data e Model geometry e Texture patterns e General data base information Description of Supported Formats The following S1000 database structures are not accessed by the loader since they are two dimensional representations of the database terrain and features e Pole sets e Defragmented Terrain Areal Features The S1K Loader does not currently support loading dynamic models with articulated parts though support is planned in future releases Control File The S1000 data base loader uses the concept of a control file to control the database load An S1K control file is an ascii file that substitutes for the formatted database file common to other loaders The control file must have a s1k file suffix to be recognized as an S1K control file Keyword and parameter value pairs specified by the user are placed in the control file to tailor the database load to the user s requirements Examples of control file parameters are S1KPROJ lt project_directory gt ROJECT lt project_name gt EMBLY_PREFIX lt assembly_prefix gt EFARCH_WINDOW lt xmin gt lt ymin gt lt xmax gt lt ymax gt RIGIN lt x gt lt y gt As v n
16. The bits PFTRAV_IS_CLIP_END and PFTRAV_IS_CLIP_START cause the segment to be clipped at the end or at the start using the intersection point By default in the absence of a discriminator segments are end clipped at each successful intersection at the finest level bounding box or primitive level requested Hence the closest intersection point is always returned The discriminator is passed a pfHit You can use pfQueryHit to examine information about the intersection including which segment number within the pfSegSet the intersection is for and the current segment as clipped by previous intersections General Math Routine Example Program General Math Routine Example Program Example 11 5 demonstrates the use of many of the available IRIS Performer math routines Example 11 5 Intersection Routines in Action simple test of pfCylIsectSeg Se pfVec3 tmpvec pfSetVec3 pt1 2 0f 0 0f 0 0f pfSetVec3 pt2 2 0f 0 0f 0 0f pfMakePtsSeg amp segl pt1 pt2 pfSetVec3 cyll axis 1 0f 0 0f 0 0f pfSetVec3 cyll center 0 0f 0 0f 0 0f cyll radius 0 5f cyll halfLength 1 0f isect pfCylIsectSeg amp cyll amp segl amp tl amp t2 pfClipSeg amp clipSeg amp segl tl t2 AssertFloatEq clipSeg length 2 0f clipSeg length pfSetVec3 tmpvec 1 0f 0 0f 0 0f AssertVec3Eq clipSeg dir tmpvec clipSeg dir pfSetVec3 tmpvec 1 0f 0 0f 0 0f AssertVec3Eq clipSeg pos tmpvec
17. The pfTexture reference page describes these details Automatic Texture Coordinate Generation Automatic texture coordinate generation is provided with the pfTexGen state attribute pfTexGen closely corresponds to IRIS GL s texgen and OpenGL s glTexGen functions When texture coordinate generation is enabled a pfTexGen applied with pfApplyTGen will automatically generate texture coordinates for all rendered geometry Texture coordinates are generated from geometry vertices according to the texture generation mode set with pffGenMode Available modes and their function are listed 347 Chapter 10 libpr Basics 348 in Table 10 13 Some modes refer to a plane which is set with pfTGenPlane Table 10 13 Texture generation modes PFTG_ Mode Token Texture coordinates are calculated as OBJECT_PLANE distance of vertex from plane in object coordinates EYE PLANE distance of vertex from plane in eye coordinates The plane is transformed by the inverse of the ModelView matrix when the pfTexGen is applied EYE_PLANE_IDENT distance of vertex from plane in eye coordinates The plane is not transformed by the inverse of the ModelView matrix when the pfTexGen is applied SPHERE _ MAP an index into a 2D reflection map based on vertex position and normal Specifics of the calculation are found in the graphics libraries man pages Lighting IRIS Performer lighting is an extension of graphics library lighting see
18. Use pfChanViewOffsets chan xyz hpr to specify additional translation and rotation offsets for the viewpoint and direction xyz specifies a translation vector and hpr specifies a heading pitch roll rotation vector Viewing offsets are automatically added each frame to the view direction specified by pfChanView or pfChan ViewMat For example to create three different perspectives of the same scene as displayed by three windows in an airplane cockpit use azimuth offsets of 45 0 and 45 for left middle and right views To create vertical view groups such as might be seen through the windscreen of a helicopter use both azimuth and elevation offsets Once the view offsets have been set up you need only set the view once per frame View offsets are applied after the eyepoint position and gaze direction have been established As with the other angles be aware that the conventions for measuring azimuth and elevation angles vary between graphics systems so you should verify that the sense of the angles is correct 97 Chapter 4 Setting Up the Display Environment 98 Example of Channel Use Example 4 7 shows how to use various pfChannel related functions The code is derived from IRIS Performer sample programs Example 4 7 Using pfChannels main pfiInit pfConfig TInitScene InitPipe InitChannel Application main loop while SimDone void InitChannel void pfChannel chan
19. You may have application state associated with pfPipe stages and processes that need special initialization For this purpose you may provide a stage configuration callback for each pfPipe stage using pfStageConfigFunc pipe stageMask configFunc and specify the pfPipe the stage bitmask including one or more of PFPROC_APP PFPROC_CULL and PFPROC_DRAW and your stage configuration callback routine At any time you may call the function pfConfigStage from the application process to trigger the execution of your stage configuration callback in the process associated with that pfPipe s stage The stage configuration callback will be invoked at the start of that stage within the current frame the current frame in the application process and subsequent frames through the cull and draw phases of the software rendering pipeline Use a pfStageConfigFunc callback function to configure performer processes not associated with pfPipes such as the database process PFPROC_DBASE and the intersection process PFPROC_ISECT A common process initialization task for real time applications is the selection and or specification of a CPU on which to run The final part of pfPipe initialization is the specification of the graphics hardware pipeline or screen and the creation of a window on that screen The screen of a pfPipe can be set explicitly using pfPipeScreen Under single pipe operation pfPipes can also inherit the screen of their first opened
20. a gt Groung fog A Figure 8 1 Layered Atmosphere Model The lowest layer consists of ground fog extending from the ground up to a user selected altitude The fog thins out with increasing altitude disappearing entirely at the bottom of the general visibility layer This layer extends from the top of the ground fog layer to the bottom of the cloud 233 Chapter 8 Creating Visual Effects 234 layer s lower transition zone if such a zone exists The transition zone provides a smooth transition between general visibility and the cloud layer If there is no cloud layer then general visibility extends upward forever The cloud layer is defined as an opaque region of near zero visibility you can set its upper and lower boundaries You can also place another transition zone above the cloud layer to make the clouds gradually thin out into clear air Set up the atmospheric simulation with the commands listed in Table 8 1 Table 8 1 pfEarthSky Routines Function Action pfNewESky Create a pfEarthSky pfESkyMode Set the render mode pfESkyAttr Set the attributes of the earth and sky models pfESkyColor Set the colors for earth and sky and clear pfESkyFog Set the fog functions You can set any pfEarthSky attribute mode or color in real time Selecting the active pfFog definition can also be done in real time However changing the parameters of a pfFog once they are set isn t advised when in multiprocessing
21. else done 0 tmpBuf j c tmpBuf PF_MAX2 j 2 0 0 Create new libpr pfString structure to attach to pfText curStr pfNewString pfGetSharedArena Set the font for the libpr pfString pfStringFont curStr fnt Assign the char string to the pfString pfStringString curStr tmpBuf Add this libpr pfString to the pfText node Like adding a libpr pfGeoSet to a pfGeode pfAddString txt curStr pfAddChild SceneGroup txt pfBillboard Nodes A pfBillboard is a pfGeode that rotates its children s geometry to follow the view direction or the eyepoint Billboards are useful for portraying complex objects that are roughly symmetrical in one or more axes The billboard rotates to always present the same image to the viewer using far fewer polygons than a solid model uses In this way billboards reduce both Node Types transformation and pixel fill demands on the graphics subsystem at the expense of some additional host processing A classic example is a textured billboard of a single quadrilateral representing a tree Because a pfBillboard is also a pfGeode you can pass a pfBillboard argument to any pfGeode routine To add geometry call pfAddGSet see pfGeode Nodes on page 137 Each pfGeoSet in the pfBillboard is treated as a separate piece of billboard geometry each one turns so that it always faces the eye point pfBillboards can be either constrained to rot
22. happen here Any graphics library functionality outside IRIS Performer must be done here void DrawFunc pfChannel chan void data pre Draw tasks like clearing the viewport PreDraw chan data pfDraw render the frame draw HUD read IRIS GL devices and so on PostDraw chan data Process Callbacks and Passthrough Data Cull and draw callbacks are specified on a per pfChannel basis using the functions pfChanTravFunc with PFTRAV_CULL and PFTRAV_DRAW respectively pfAllocChanData allocates passthrough data data which is passed down the rendering pipeline to the callbacks In the cull phase of the rendering pipeline IRIS Performer invokes the cull callback with a pointer to the pfChannel that is being culled and a pointer to the pfChannel s passthrough data buffer The cull callback may modify data in the buffer The potentially modified buffer is then copied and passed to the user s draw callback Process Callbacks Default IRIS Performer processing is triggered by pfCull and pfDraw By default pfFrame calls pfCull first then calls pfDraw If process callbacks are defined however pfCull and pfDraw are not invoked automatically and must be called by the callbacks to use IRIS Performer s default processing pfCull should be called only in the cull callback it causes IRIS Performer to cull the current channel and to generate a display list suitable for rendering
23. initial ref count is 0 mt1B pfNewMtl arena initial ref count is 0 Attach mtlA to gstate0 Reference count of mtlA is incremented pfGStateAttr gstate0 PFSTATE_FRONTMTL mtlA 49 Chapter 2 IRIS Performer Basics 50 Attach mt1B to gstatel Reference count of mt1B is incremented pfGStateAttr gstatel PFSTATE_FRONTMTL mt1B gstatel gstate0 The reference counts of mtlA and mt1B are 2 and 0 respectively Note that mt1B is NOT deleted even though its reference count is 0 pfCopy gstatel gstate0 Determining Object Type Sometimes you have a pointer to a pfObject but you don t know what it really is is it a pfGeoSet a pfChannel or something else pfGetType returns a pfType which specifies the type of a pfObject This pfType can be used to determine the class ancestry of the object Another set of routines one for each class returns the pfType corresponding to that class e g pfGetGroupClassType returns the pflype corresponding to pfGroup Since pfTypes are most frequently used to answer the question is object A of class B a helper function pflsOfType performs the test without the explicit use of a pfType With these functions you can test for class type as shown in Example 2 5 Example 2 5 General Purpose Scene Graph Traverser void travGraph pfNode node if pfIsOfType node pfGetDCSClassType doSomethingTransforming node If
24. libfm IRIS GL font manager required by libpfutil with IRIS GL libm Math library required by libpr libfpe Floating point exception library required by libpr libmalloc Memory allocation library libC C library required by libpf For an IRIS GL application using all of the libraries included with IRIS Performer the link line should include lpfdu_igl lpfui lpfutil_igl lpf_igl limag lgl 1Xmu 1X11 1m lfp lfm lmalloc 1C The corresponding line for an OpenGL application would be lpfdu_ogl lpfui lpfutil_ogl lpf_ogl limag IGLU 1GL 1lXext 1Xmu 1X11 lm lfp imalloc 1C Dynamic Shared Objects DSOs The standard libraries for IRIS Performer are distributed as dynamic shared objects Compared with static libraries DSOs produce smaller applications and allow sharing between multiple executables that are running simultaneously However if you build an application using a DSO that DSO must be present on the target system at run time The DSOs for IRIS Performer 2 0 are in the performer_eoe subsystem on the IRIS Performer CD ROM Debug and Static Libraries IRIS Performer also ships with the its libraries in different forms that might be useful to developers The debug versions are primarily intended for bug reporting because they contain more symbol table information than the optimized versions The static versions are for use when distributing an application to customers who may not have performer_
25. major league from the minor league in visual simulation technology e Real time character animation Real time character animation in entertainment systems is based on features and capabilities originally developed for high end flight simulators Creation of compelling entertainment experiences hinges on the ability to provide engaging synthetic characters e Database construction One of the key notions of real time image generation systems is the fact that they are often programmed largely by their databases This programming includes the design and specification of several autonomous actions for later playback by the visual system Survey of Visual Simulation Techniques Low Latency Image Generation The issue of latency is critical to comfortable perception of moving images under interactive control In the real world the images that reach our brains move smoothly and instantly in reaction to our own motion In simulated visual environments such motion is usually depicted as a discrete series of images generated at fixed time intervals Furthermore the image resulting from a motion often is not presented until several frame intervals have elapsed creating a very unnatural latency A typical human reaction to such delayed images is a nausea commonly known as simulator sickness In visual simulation the terms latency and transport delay refer to the time elapsed between stimulus and response Confusion can en
26. or jump directly to whatever chapter covers the specific topic you re interested in Source code for perfly is provided beneath usr share Performer src sample C in the perfly and common directories so that you can incorporate parts of these programs into your own applications A C version can be found under usr share Performer src sample C Exploring the IRIS Performer Sample Scenes The perfly application is a fairly basic visual simulation program that can load and store scene databases in any of a wide variety of common formats and display the resulting scenes This section describes how to use perfly to look at several sample databases provided with IRIS Performer perfly provides a graphical user interface with which you can control many of the visual simulation features that are described in this guide such as time of day selection haze density and so on These options all default to reasonable values so you don t need to learn about them before using perfly Installing the Software Follow the instructions in the IRIS Performer Release Notes to install the software This process places the appropriate libraries header files sample databases reference pages on line books and demonstration programs on your system Chapter 1 Getting Acquainted With IRIS Performer Figure 1 1 A Section of the New Jerusalem City Hall Starting and Quitting perfly To launch perfly type IRIS perfly d chamber 0 1lsa N
27. pfLoadTexFile tex spotlight inta pfLSourceMode proj PFLS_PROJTEX_ENABLE 1 pfLSourceAttr proj PFLS_PROJ_FRUST shadFrust pfLSourceAttr proj PFLS_PROJ_TEX tex pfLSourceColor proj PFLT_DIFFUSE 0 0f 0 0f 1 0f pfLSourceVal proj PFLS_INTENSITY 5f pfLSourcePos proj 0 0f 0 0f 0 0f 1 0f make local Add to DCSes so we can move lights around shadDCS pfNewDCS pfAddChild shadDCS shad pfAddChild scene shadDCS proj jDCS pfNewDCS pfAddChild projDCS proj pfAddChild scene pro jDCS For scenes with multiple pfLightSources you can scale the contribution from each source with the PFLS_INTENSITY value so that the total illumination from all sources does not exceed one Otherwise lighted geometry may become saturated and not look real pfLightSources which are located near the eyepoint and which project a texture to simulate spotlights can attenuate the spotlight based on range by using a pfFog to define the falloff ramp The pfFog is set with the PFLS_PROJ_FOG token to pfLSourceAttr and should have the same color as the lighting ambient Morphing Morphing is the smooth transition from one particular appearance to another Morphing can refer to images or geometry colors texture coordinate or coordinates For example you could morph the following e the image of a person s face into that of another person e color to simulate a
28. pfRemoveString Remove a pfString pfInsertString Insert a pfString pfReplaceString Replace a pfString pfGetString Supply a pointer to the specified pfString pfGetNumStrings Determine how many pfStrings are in the given pfText Using the pfText facility is easy Example 5 11 shows how a pfFont is defined how pfStrings are created that reference that font and then how those pfStrings are added to a pfText node for display See the description of pfStrings and pfFonts in Chapter 10 libpr Basics for information on setting up individual strings to input into a pfText node Example 5 11 Adding pfStrings to a pfText int nStrings i char tmpBuf 8192 char fontName 128 pfFont fnt NULL Create a new text nod pfText txt pfNewText Read in font using libpfdu utility function scanf s fontName fnt pfdLoadFont typel fontName PFDFONT_EXTRUDED Cant render pfText or libpr pfString without a pfFont if fnt NULL pfNotify PFNFY_WARN PFNFY_PRINT No Such Font s n fontName 139 Chapter 5 Nodes and Node Types 140 Read nStrings text strings from standard input and Attach them to a pfText scanf d amp nStrings for i 0 i lt nStrings i char c int j 0 int done 0 pfString curStr NULL while done lt 2 READ STRING END on c getchar if c donet t
29. pfUpdatePart Traverse the partition s children and incorporate changes pfGetPartType Determine what kind of partition is being used Example 5 13 demonstrates setting up and using a pfPartition node Example 5 13 Setting Up a Partition pfGroup terrain pfPartition partition pfScene scene terrain read_in_grid_aligned_terrain create a default partitioning of a terrain grid partition pfNewPart pfAddChild scene partition pfAddChild partition terrain pfBuildPart partition use the partitions to perform efficient intersections of sets of segments with the terrain for i 0 i lt numVehicles i 145 Chapter 5 Nodes and Node Types Sample Program 146 pfNodelIsectSegs partition vehicle_segment_set i NIT Seruct 3 The sample program shown in Example 5 14 demonstrates scene graph construction shared instancing and transformation inheritance The program uses IRIS Performer objects and functions that are described fully in later chapters This program reads the names of two objects from the command line although defaults are supplied if file names are not given These files are loaded and a second instance of each object is created In each case this instance is made to orbit the original object and the second pair are also placed in orbit around the first This program is inherit c and is part of the suite of IRIS Performer Programmer s Guide examp
30. s geometry to a display list for pfGeodes If the cull result was PFIS_ALL_IN view frustum culling is disabled during the traversal of the children If a post draw callback is defined then place a libpr display list packet in the display list so that the node s post draw callback will be called by the draw process If running a combined CULLDRAW traversal invoke the post draw callback directly instead If a post cull callback is defined then call the post cull callback Draw callbacks are commonly used to place tags or change state while a subgraph is rendered Note that if the pre draw callback is called the post draw callback is guaranteed to be invoked This way the callback can restore any state modified by the pre draw callback This is useful for state changes such as pfPushMatrix and pfPopMatrix as shown in the environment mapping code that s part of Example 6 2 Controlling and Customizing Traversals For doing customized culling the pre cull callback can determine whether a PFIS_ALL_IN has already turned off view frustum culling using pfGetParentCullResult in which case it may not wish to do its own cull testing It can also find out the result of the standard cull test by calling pfGetCullResult Cull callbacks can also be used to render geometry pfGeoSets or change graphics state Any libpr drawing commands are captured in a display list and are later executed during the draw traversal see Display L
31. type Table 10 2 lists the primitive type tokens the primitive types that they represent and the number of vertices in a coordinate list for that type of primitive Table 10 2 Geometry Primitives Token Primitive Type Number of Vertices PFGS_POINTS PFGS_LINES PFGS_LINESTRIPS PFGS_FLAT_LINESTRIPS PFGS_TRIS Points numPrims Independent line segments 2 numPrims Strips of connected lines Sum of lengths array Strips of flat shaded lines Sum of lengths array Independent triangles 3 numPrims 321 Chapter 10 libpr Basics 322 Table 10 2 continued Geometry Primitives Token Primitive Type Number of Vertices PFGS_TRISTRIPS Strips of connected triangles Sum of lengths array PFGS_FLAT_TRISTRIPS Strips of flat shaded triangles Sum of lengths array PFGS_QUADS Independent quadrilaterals 4 numPrims PFGS_POLYS Independent polygons Sum of lengths array where the parameters in the last column represent numPrims is the number of primitive items in the pfGeoSet as set by pfGSetNumPrims lengths is the array of strip lengths in the pfGeoSet as set by pfGSetPrimLengths note that length is measured here in terms of number of vertices Connected primitive types line strips triangle strips and polygons require a separate array that specifies the number of vertices in each primitive Length is defined as the number of vertices in a strip for STRIP primitives and is the number of vertices in a p
32. 0 0f determine extent of scene s geometry pfGetNodeBSphere root amp bsphere pfChanNearFar chan 1 0f 10 0f bsphere radius Simulate for twenty seconds while t lt 20 0f pfCoord view float Ay c 57 Chapter 3 Building a Visual Simulation Application 58 pfi Compute new view position t pfGetTime pfSinCos 45 0f t amp s amp c pfSetVec3 view hpr 45 0f t 10 0f 0 pfSetVec3 view xyz 2 0f bsphere radius s 2 0f bsphere radius c 0 5f bsphere radius pfChanView chan view xyz view hpr Initiate cull draw for this frame pfFrame Terminate parallel processes and exit Exit If you would like to compile simple c and try it out use the copy in usr share Performer src pguide libpf C the Makefile in that directory provides all the necessary compilation options For more information about IRIS Performer compiler options see the Compiling and Linking IRIS Performer Applications section of this chapter Once you ve compiled the code try executing it with some of the sample data files in usr share Performer data such as blimp flt or sampler nff Here s a description of the steps involved in a simple IRIS Performer application Refer to the sample code in Example 3 1 as you read through these steps 1 Include the necessary system header files include lt stdlib h gt Include the relevant IRIS
33. 0 52700269 0 32859191 1 00 Arcturus s 0 18718566 0 73014212 0 65715599 1 00 Capella s 0 12507832 0 76942003 0 62637711 0 99 Vega s 0 13051330 0 68228769 0 71933979 0 99 Capella s 0 19507207 0 97036278 0 14262892 0 98 Rigel s 0 37387931 0 31261155 0 87320572 0 94 Rigil Kentaurus Description of Supported Formats s 0 41809806 0 90381104 0 09121194 0 94 Procyon s 0 49255905 0 22369388 0 84103900 0 92 Achernar pfdLoadFile uses the function pfdLoadFile_star to load Star format files into IRIS Performer run time data structures 3D Lithography STL Format The STL format is used to define 3D solids to be imaged by 3D lithography systems STL defines objects as collections of triangular facets each with an associated face normal The ASCII version of this format is known as STLA and has a very simple structure The image in Figure 9 13 shows a typical STLA mechanical CAD database This model is defined in the bendix stla sample data file Figure 9 13 Sample STLA Database 309 Chapter 9 Importing Databases 310 The source code for the STLA format loader is in the files usr share Performer src libflibpfdb libpfstla pfstla c STLA format files have a line structured ASCII form an initial keyword defines the contents of each line of data An STLA file consists of one or more facet definitions each of which contains 1 the facet normal indicated with the facet normal keyword 2 the facet vertices bracketed
34. 0 88243 0 96366 14 0329 0 0502096 4 44467 1 24 026 13 5669 0 0363863 2 37938 2 17479 13 3626 0 0363863 poly3dn 4 text 2 37938 2 17 4 44467 1 24 tured 479 13 3626 0 0363863 026 13 5669 0 0363863 0 234553 0 0 376701 0 0 337291 0 0 337291 0 0 337291 0 0 337291 0 969676 0 1 924973 0 0 75 940697 0 0909091 0 75 940697 0 0909091 1 940697 0 0909091 1 940697 0 0909091 0 75 313 Chapter 9 Importing Databases 314 9 23775 2 34664 13 1475 0 0344832 0 284369 0 958095 0 181818 0 75 6 69592 3 94535 12 6716 0 0344832 0 284369 0 958095 0 181818 1 This excerpt specifies material properties and references texture images stored in the files prchmnt rgb and wood rgb and then defines two polygons pfdLoadFile uses the function pfdLoadFile_sv to load SuperViewer files into IRIS Performer run time data structures Geometry Center Triangle Format The tri format is used at the University of Minnesota s Geometry Center as a simple geometric data representation The loader was developed by inspection of a few sample files The IRIS Performer tri loader is in the usr share Performer srcflibflibpfdb libpftri directory These files have a very simple format a line per vertex with position and normal given on each line as 6 ASCII numeric values The file is simply a series of these triangle definitions Here are the first two triangles from the data file usr sha
35. 16 18 FTP site xxxv getting started xxvii graphics libraries 40 initializing See pfInit installing 3 introduction xxv libraries 13 29 38 mailing list xxxv naming conventions 35 ordering documentation xxx release notes 3 sample programs 3 type system 50 482 483 491 web page xxxv why use IRIS Performer xxv IRIX kernel 474 IRTP format See formats J Johnson Nelson 279 Johnston Eric xxix Jones Michael xxix Jump Dennis N 279 K Kalawsky Roy S xxxiii Kaleido polyhedron generator 295 kernel 474 keyframing using quaternions for 404 Kichury John 311 L latency 21 controlling 457 defined 519 total 21 transport delay 21 visual 21 541 Index latency critical definition 519 updates 457 layer geometry 338 definition 519 layering internal software structure 14 level of detail 23 blended transitions 208 cannonical channel resolution 204 cannonical field of view 204 defined 520 stress management switching 130 use in optimization 451 Lewis Frank L xxxii libpf 13 defined 520 overview 17 libpfdb 251 libpfdu 13 251 252 defined 520 geometry builder 36 overview 18 libpfui 14 drive model 4 flight model 6 overview 18 libpfutil 14 251 defined 520 overview 18 libpr 13 and libpf 317 defined 520 description 317 graphics state 333 overview 16 libpr classes 520 library names 40 lighting 542 directional 23
36. 210 sufficiently accurate or is recursively subdivided The general manner of subdivision is to introduce one or more vertices along the sides of the original triangle Connecting these new vertices to make triangles leads to the subdivision of the original triangle into multiple triangles After subdivision the algorithm perturbs the vertex positions If the resulting triangles are not yet sufficiently fine the subdivision process is applied to each one in turn based on range and other fidelity criteria Arbitrary Morphing Terrain level of detail using an interpolative active surface definition is a restricted form of the more general notion of object morphing Morphing of models such as the car in a previous example can simply involve scaling a small detail to a single point and then removing it from the scene Morphing is possible even when the topologies of neighboring pairs do not match Both models and terrain can have vertex normal color and appearance information interpolated between two or more representations The advantages of this approach include reduced graphics complexity since blending is not used constant intersection truth for collision and similar tasks and monotonic database complexity that makes system load management much simpler Because the effects of variable image update rates can be objectionable many simulation applications are designed to operate at a fixed frame rate One approach to selecting this fixed f
37. 414 See also pfSegSet semaphores allocating 388 sense definition of 526 setmon 385 setrlimit 388 SGF format See formats SGO format See formats shading 25 flat 337 Gouraud 337 556 shadow map 242 defined 526 shadows 85 242 shared arena memory mapping 387 shared instancing 120 defined 526 shared memory allocation 486 arenas 386 388 datapools 388 debugging and 474 initializing 62 sharing channel attributes 105 sharpen texture 465 shininess definition 527 Shoemake Ken xxix siblings of a node defined 527 Sierpinski sponge 38 251 308 SIGGRAPH xxix Silicon Graphics Object format See formats SIMNET 300 simple c example program 55 simulation based design xxv simulation loop 65 simulator sickness 21 single inheritance 45 single precision arithmetic 466 skeleton animation 28 sky 32 Software Systems 280 Soma cube puzzle 276 sorting 24 defined 527 sorting for transparency 337 source code 9 58 77 83 89 90 91 142 157 169 205 238 245 251 254 259 343 352 374 376 377 378 381 433 434 443 457 459 460 465 470 491 524 sample code 28 source code examples xxviii source code tour 55 spacing character 328 definition 527 sparkle 24 spatial organization 163 definition 527 SPF format See formats spheres as bounding volumes 408 SPIE xxxiv SPONGE format See formats spotlights 242 sprite 353 defined 527 sproc 226 391
38. 421 Chapter 12 Statistics This chapter discusses the various kinds of available statistics on the performance of your application Chapter 12 Statistics This chapter describes the IRIS Performer profiling utilities Statistics are available on nearly every aspect of IRIS Performer s operation and can be used to diagnose both functionality and performance problems as well as for writing benchmarks and for load management For more detailed information on interpreting statistics to tune the performance of your application refer to Chapter 13 Performance Tuning and Debugging To collect most IRIS Performer statistics all you have to do is enable them IRIS Performer then collects them automatically for you in pfStats and pfFrameStats data structures for libpr and libpf respectively You can query the contents of these structures from your program or write the data to files A libpf application can also display the contents of a pfFrameStats structure ina channel by calling pfDrawChanStats or pfDrawFStats The statistics drawn for a channel are the statistics accumulated in the channel s own pfFrameStats Such a display isn t necessary for statistics collection The pointer to the pfFrameStats structure for a channel can be gotten with pfGetChanF Stats You can then control which statistics for the channel are being accumulated Most of the IRIS Performer demo programs display some subset of these stat
39. A pfPipeWindow can be created for a pfPipe using pfNewPWin pipe If you create a pfPipeWindow then you are responsible for explicitly opening it The call to pfOpenPWin pwin from the application process will cause the next call to pfFrame to trigger the opening of the pfPipeWindow in the draw process A pfPipeWindow created in the application will be a rubber band window of undefined size for the user to stretch out This is in contrast to the full screen window that IRIS Performer creates on your behalf in the fully automatic case To easily get a full screen window you can use the pfPWinFullScreen function pfPWinOriginSize can be used to set a fixed position and size for the window The code in Example 4 2 placed in the application process will create and open a window in the lower left corner of the screen of size 500 pixels on each side 79 Chapter 4 Setting Up the Display Environment 80 Example 4 2 Creating a pfPipeWindow main pfPipe pipe pfPipeWindow pwin pfiInit pfConfig Create pfPipeWindow for pfPipe 0 pipe pfGetPipe 0 pwin pfNewPWin pipe Set the origin and size of the pfPipeWindow pfPWinOriginSize pwin 0 0 500 500 Tell IRIS Performer that the pfPipeWindow is ready to be opened Hf pfOpenPWin pwin trigger the opening of the pfPipeWindow in the draw process Hp pfFrame while SimDone pfPipeWindows are actually built upon li
40. Channels culled by pfCull may be drawn in the draw callback by pfDraw It is legal for the draw callback to call pfDraw more than once Multi pass renderings performed with multiple calls to pfDraw are typical when you use accumulation buffer techniques When the draw callback is invoked the window will have already been properly configured for drawing the pfChannel Specifically the viewport perspective and viewing matrices are set to their correct values User modifications of these values are not reset by pfDraw If a draw callback is specified IRIS Performer doesn t automatically clear the viewport it leaves that responsibility to the application pfClearChan can be called from the draw callback to clear the channel viewport If chan has a pfEarthSky then the pfEarthSky is drawn Otherwise the viewport is cleared to black and the z buffer is cleared to its maximum value You should call pfPassChanData to indicate that user data should be passed through the rendering pipeline which propagate the data downstream to cull and draw callbacks The next call to pfFrame copies the channel buffer into internal buffers so that the application is then free to modify data in the buffer without fear of corruption The pfPassChanData function should be called only when necessary since calling it imposes some buffer copying overhead In addition passthrough data should be as small as possible to reduce the time spent copyin
41. Example 5 1 Example 5 2 Example 5 3 Example 5 4 Example 5 5 Example 5 6 Example 5 7 Example 5 8 Example 5 9 Example 5 10 Example 5 11 Example 5 12 Objects and Reference Counts 47 Using pfDelete with libpr Objects 47 Using pfDelete with libpf Objects 48 Using pfCopy 49 General Purpose Scene Graph Traverser 50 Structure of an IRIS Performer Application 56 pfPipes in Action 77 Creating a pfPipeWindow 80 pfPipeWindow with alternate configuration windows 84 Custom initialization of pfPipeWindow state 85 Configuration of a pfPipeWindow Framebuffer 89 Opening and Closing a pfPipeWindow 90 Using pfChannels 98 Multiple Channels One Channel per Pipe 103 Channel Sharing 107 Making a Scene 116 Hierarchy Construction Using Group Nodes 118 Creating Cloned Instances 123 Automatically Updating a Bounding Volume 124 Using pfSwitch and pfSequence Nodes 129 Marking a Runway With a pfLayer Node 132 Setting Up Light Points 133 pfLightSource Pointers and Multiple Inheritance 134 Car Headlights as pfLightSource Nodes 134 Adding pfGeoSets to a pfGeode 138 Adding pfStrings to a pfText 139 Setting Up a pfBillboard 142 XV Examples xvi Example 5 13 Example 5 14 Example 6 1 Example 6 2 Example 6 3 Example 6 4 Example 7 1 Example 7 2 Example 7 3 Example 8 1 Example 8 2 Example 8 3 Example 8 4 Example 10 1 Example 10 2 Example 10 3 Example 10 4 Example 10 5 Example 10 6 Example 10 7 Example 10 8 Example 10
42. Imdef 3g for IRIS GL or glLight and related functions in OpenGL but IRIS Performer divides the actions of Imdef into lights and light models just as OpenGL does The light embodies the color position and type for example infinite or spot of the light The light model specifies the environment for infinite the default or local viewing and two sided illumination pfLights and pfLightModels are created by calling pfNewLight and pfNewLModel respectively The transformation matrix that is on the matrix stack at the time the light is applied controls the interpretation of the light source direction 1 To attach a light to the viewer like a miner s head mounted light call pfLightOn only once with an identity matrix on the stack 2 To attach a light to the world like the sun or moon call pfLightOn every frame with only the viewing transformation on the stack 3 To attach a light to an object like the headlights of a car call pfLightOn every frame with the combined viewing and modeling transformation on the stack Graphics State The number of lights you can have turned on at any one time is limited by PF_MAX_LIGHTS just as is true with the graphics libraries Note In IRIS GL attenuation is also part of the light model definition In OpenGL attenuation is defined per light There is separate libpr API for setting each of these pfLModelAtten for IRIS GL and pfLightAtten for OpenGL You can u
43. PFMP_CULLoDRAW model in which the cull and draw stages for a given frame are performed in tandem in this mode d0 is directly below c0 in the 427 Chapter 12 Statistics 428 graph In Figure 12 1 the PFMP_APP_CULL_DRAW model was used and all stages are part of separate processes These stage timings are helpful when choosing a process model and balancing the cull and draw tasks for a database Furthermore the timing graph can show you how close you are to an improvement in frame rate as you view the database The timing lines for each stage are broken into pieces displayed at slightly different heights and thicknesses to show the time taken by significant subtasks within each stage Raised segments reflect time spent in user code intermediate lines reflect time spent in IRIS Performer code and lowered lines reflect time waiting on other operations The application stage is divided into five subsegments e The time spent in the application s main loop between the pfFrame call and the pfSync call drawn as a raised line e The time spent cleaning the scene graph during pfSync e The time spent sleeping in pfSync while waiting for the next frame boundary drawn as a low thin pale dotted line e The time spent in the application code between calling pfSync Q and calling pfFrame drawn as bright raised line e The time spent in pfFrame cleaning the scene graph after any changes that might have been made
44. Table 6 4 Table 6 5 Table 6 6 Table 7 1 Table 7 2 Table 7 3 IRIS Performer Libraries 13 Routines that Modify libpr Object Reference Counts 46 pfPWinType Tokens 81 Processes from which to call main pfPipeWindow functions 88 Attributes in the Share Mask of a Channel Group 106 IRIS Performer Node Types 114 pfGroup Functions 117 DCS Transformations 127 pfSequence Functions 128 pfLOD Functions 130 pfLayer Functions 131 pfLightPoint Functions 132 pfLightSource Functions 137 pfGeode Functions 138 pffext Functions 139 pfBillboard Functions 141 pfPartition Functions 145 Traversal Attributes for the Major Traversals 154 Cull Callback Return Values 171 Intersection Query Token Names 180 Database Classes and Corresponding Node Masks 182 Representing Traversal Mask Values 183 Possible Traversal Results 184 Frame Control Functions 193 LOD Transition Zones 208 Multiprocessing Models 215 xxi Tables xxii Table 7 4 Table 8 1 Table 8 2 Table 9 1 Table 9 2 Table 9 3 Table 9 4 Table 9 5 Table 9 6 Table 9 7 Table 9 8 Table 9 9 Table 10 1 Table 10 2 Table 10 3 Table 10 4 Table 10 5 Table 10 6 Table 10 7 Table 10 8 Table 10 9 Table 10 10 Table 10 11 Table 10 12 Table 10 13 Table 10 14 Table 10 15 Table 10 16 Table 10 17 Table 10 18 Table 10 19 Table 10 20 Table 10 21 Trigger Routines and Associated Processes 225 pfEarthSky Routines 234 pfEarthSky Attributes 234 Database Importer Source Direc
45. When you release the button you ll continue gliding forward at constant speed and can hold down the middle mouse button to steer Tap the middle mouse to stop in front of the building if you actually entered the building remember the Reset All button Now accelerate backward by pressing the right button When you re as far back as you want to go hold down the left mouse button to gradually slow down or tap the middle mouse button to stop immediately Now use the left mouse button again to start moving forward and drive slowly into the model Notice that the walls closest to you are cut away at first so you can see inside once you re completely inside the building those walls reappear Drive around and explore the building Tap the middle mouse button to stop before you run into anything but don t worry at this point you ll bounce off of any walls you hit If the walls get in your way you can turn off collision detection with the button labeled Collide on the control panel or press the c key on the keyboard More Controls To see the underlying geometry used to create the model click the Style button in the control panel or press the w key on the keyboard This changes the display to wireframe mode In this mode you can more easily see how Chapter 1 Getting Acquainted With IRIS Performer many polygons are used to represent an object This information can be helpful when you re tuning a database becau
46. are in its current pfBuffer As a result a database process may not directly add a newly created subgraph of nodes to the main scene graph because all nodes in the main scene graph have application buffer scope only they are isolated from the database pfBuffer This may seem inconvenient at first but it eliminates catastrophic errors like for example the application process traverses a group at the same time you add a child changing its child list and causing the traversal to chase a bad pointer Remedies to the inconveniences stated above are the pfBufferAddChild pfBufferRemoveChild and pfBufferClone routines The first two routines are identical to their non buffer counterparts pfAddChild and pfRemoveChild except the buffer versions do not happen immediately Other functions pfBufferAdd pfBufferInsert pfBufferReplace and pfBufferRemove perform the buffer oriented delayed action versions of the corresponding non buffer pfList functions In all cases the add insert replace or removal request is placed on a list in the current pfBuffer and is processed later at pfMergeBuffer time pfBufferClone supports the notion of maintaining a library of common objects like trees or houses in a special library pfBuffer The main database process then clones objects from the library pfBuffer into the database pfBuffer possibly pfFlatten ing them for improved rendering performance pfBufferClone is identical to pfClone
47. engineering effort required to accurately embed those 966 ball bearings 19 Chapter 2 IRIS Performer Basics 20 This section outlines the major requirements of current visual simulation systems These requirements fall into six major groups each covering several related topics e Low latency image generation Reducing perceived latency the time between input and response requires reducing both actual latency and frame rate You cannot avoid latency but you can minimize its effects by attention to hardware design and software structure e Consistent frame rates A fixed frame rate is essential to realistic visual simulation Achieving this goal however is very difficult because it requires using a fixed graphics resource to view images of varying complexity To design for constant frame rates you must understand the required compromises in hardware database and application design e Rich scene content Customers nearly always want complex detailed and realistic images without sacrificing high update rates and low system cost Thus providing interesting and natural scenes is usually a matter of tricks and halfway measures a naive implementation would be prohibitively expensive in terms of machine resources e Texture mapping Texture processing is arguably the most important incremental capability of real time image generation systems Sophisticated texture processing is the factor that most clearly separates the
48. examine the file usr share Performer data fontsample2 im breakup 0 0 0 0 0 new root top end_root Description of Supported Formats new font mistr extruded Mistr 3 end_font new str_text textnode mistr extruded 1 Hello World end_text attach top textnode pfdLoadFile uses the function pfdLoadFile_im to load im format files into IRIS Performer run time data structures pfdLoadFile_im searches the current IRIS Performer file path for the named file and returns a pointer to the pfNode parenting the imported scene graph or NULL if the file isn t readable or doesn t contain a valid database AAI Graphicon IRTP Format The AAI Graphicon irtp format is used by the TopGen database modeling system and by the Graphicon 2000 image generator The name IRTP is an acronym for Interactive Real Time PHIGS The IRIS Performer irtp loader is in the usr share Performer src lib libpfdb libpfirtp directory Though loader does not support the more arcane IRTP features such as binary separating planes or a global matrix table it has served as a basis for porting applications to IRIS Performer and the RealityEngine pfdLoadFile uses the function pfdLoadFile_irtp to load IRTP format files into IRIS Performer run time data structures Silicon Graphics Open Inventor Format The Open Inventor object oriented 3D graphics toolkit defines a persistent data format that is also a superset of the VRML networked gra
49. except the buffer version requires that the source pfBuffer be specified and that all cloned nodes have scope in the source pfBuffer 221 Chapter 7 Frame and Load Control 222 pfAsyncDelete We ve discussed how to create subgraphs for database paging create and select a current pfBuffer create nodes and build the subgraph call pfBufferAddChild and finally pfMergeBuffer to incorporate the subgraph into the application s scene But what about freeing the memory of old unwanted subgraphs For this we turn to pfAsyncDelete pfDelete is the normal mechanism for deleting objects and freeing their associated memory However pfDelete can be a very costly routine since it must traverse unreference and register a deletion request for every IRIS Performer object it encounters which has a 0 reference count pfAsyncDelete in conjunction with a forked DBASE process moves the burden of deletion to the asynchronous database process so that all rendering and intersection pipelines are not adversely affected pfAsyncDelete may be called from any process and places an asynchronous deletion request on a global list that is processed later by the DBASE stage when its trigger routine pfDBase is called A major difference from pfDelete is that pfAsyncDelete does not immediately check the reference count of the object to be deleted and so does not return a value indicating whether the deletion was successful or not At this
50. increased parallelism when multiple pfChannels exist in a single IRIS Performer rendering pipeline In this case multiple cull processes are created to work on culling the channels of a pfPipe in parallel For example a single IRIS Performer pipeline stage such as the CULL is multithreaded when configured as multiple concurrent processes These threads are not arranged in pipeline fashion but work in parallel on the same frame 521 Glossary 522 mutual exclusion Controlling access to a data structure so that two or more threads in a multiprocessing application cannot simultaneously access a data structure Mutual exclusion is often required to prevent a partially updated data structure from being accessed while it is in an invalid state node An IRIS Performer libpf data object used to represent the structure of a visual scene Nodes are either leaf nodes that contain geometry via libpr or are internal nodes derived from pfGroup that control and define part of the scene hierarchy nonblocking file access A method of obtaining data from a file without having to wait for any other processes to finish using the file Such accesses involve a two step transaction in which the application first indicates the task to be performed and is given a handle This handle can later be used to inquire about the status of the file action is it in progress has it completed or has there been an error non degrading priorities Pr
51. libpfdu The pfdBuilder allows the immediate mode input of graphics state and primitives through very simple and exposed data structures After having received all of the relevant information the pfdBuilder builds efficient and somewhat optimized libpr data structures and returns a low level libpf node that can be attached to an IRIS Performer scene graph The pfdBuilder is the recommended method of importing data from non IRIS Performer based formats into IRIS Performer Creation of a Performer Database Converter using ibpfdu Creating a new format converter is very simple process More than thirty database loaders are shipped with IRIS Performer in source code form to serve as practical examples of this process The loaders read formats that range from trivial to complex and should serve as an instructive starting point for those developing loaders for other formats These loaders can be found in the directory usr share Performer src lib libpfdb libpf This section describes the libpfdu framework for creating a 3 D database format converter Let s consider writing a converter for a simple ASCII format that is called the Imaginary Immediate Mode format with the file type extension iim This format is much like the more elaborate im format loader used at SGI for the purposes of testing basic IRIS Performer functionality 259 Chapter 9 Importing Databases 260 The first thing to do is set up the routine that pfdL
52. list you can specify a list of textures to be in a texture set managed by the base texture tex The base texture is what gets applied with pfApplyTex or assigned to geometry through pfGeoStates With pfTexFrame you can select a given texture from the list 1 selects the base texture and is the default This allows you to define a texture movie where each image is the frame of the movie You can have an image on the base 345 Chapter 10 libpr Basics 346 texture to display when the movie is not playing There are additional loading modes for pfTexLoadMode described in Table 10 12 to control how the textures in the texture list share memory with the base texture Table 10 12 Texture Load Modes PFTEX_LOAD__ Load mode values Description modeToken BASE BASE_APPLY Loading of image is done as required BASE_AUTO_SUBLOAD for pfApply or automatically subloaded upon every pfApply LIST LIST_APPLY Loading of list texture image is as LIST_AUTO_IDLE separate apply causes freeing of LIST_AUTO_SUBLOAD previous list texture in hardware texture memory or is subloaded into memory managed by the base texture Texture list textures can share the exact graphics texture memory as the base texture but this has the restriction that the textures must all be the exact same size and format as the base texture Texture list textures can also indicate that they are mutually exclusive which will cause the texture memory of previous te
53. or pfInitArenas but some objects e g those in libpr may be created in any arena returned by acreate IRIS Performer calls that accept an arena pointer as an argument can also accept the NULL pointer indicating that the memory should be allocated from the heap See also heap asynchronous database paging An advanced method of scene graph creation asynchronous database paging allows desired data to be read from a disk or network connection and IRIS Performer internal data structures to be built for this data using one or more processes running on separate CPUs rather than performing these tasks in the application process Once the data structures are created in these database processes they must be explicitly merged into the application buffer 509 Glossary 510 attribute binding The binding of an attribute specifies how often an attribute is specified and the scope of each specification For example given a collection of triangles for rendering a color can be specified with each vertex of each triangle with each triangle or once for the entire collection of triangles base geometry The object with the lowest visual priority in a pfLayer node s list of children This would be the runway for example in a runway and stripes airport database example See also layer geometry bezel The beveled border region surrounding any item but most notably around the edge of a CRT monitor billboard Geometry that rot
54. pfDelete Delete the pfGeoState pfGStateMode Set a specific state mode pfGStateVal Set a specific state value pfGStateAttr Set a specific state attribute pfGStatelnherit Specify which state elements are inherited from the global state pfApplyGState Apply pfGeoState s non inherited state elements to graphics pfGetCurGState Return the current pfGeoState in effect pfGStateFuncs Assign pre post callbacks to pfGeoState pfApplyGStateTable Specify table of pfGeoStates used for indexing pfGeoState Structure Figure 10 3 diagrams the conceptual structure of a pfGeoState 361 Chapter 10 libpr Basics Figure 10 3 pfGeoState Structure 362 Windows Windows Rendering to the graphics hardware requires a window A window is an allocated area of the screen with associated framebuffer resources The X window system manages the use of shared resources amongst the different windows Windows can be requested directly from an X window server With a bit of interfacing both IRIS GL and OpenGL graphics contexts can render into X windows An X window with an IRIS GL graphics context is called a mixed model IRIS GL GLX window An X window with an OpenGL graphics context is called an OpenGL X window An X window can only have one graphics context at a time rendering to it IRIS GL supports a third option pure IRIS GL windows Pure IRIS GL windows are convenient and flexible for rendering purposes but can not be used as X
55. pfDraw 177 216 225 243 429 455 459 464 pfDrawChanStats 425 434 436 452 463 467 475 pfDrawDList 328 355 358 pfDrawFStats 425 434 436 pfDrawGSet 224 321 323 327 328 358 360 pfDrawString 224 330 332 pfdSaveBldrState 262 pfdStoreFlle 252 pfEarthSky 177 pfEnable 224 340 358 pfEnableStatsHw 434 435 438 550 pfEndSprite 353 354 pfEqualMat 402 pfEqualVec3 399 pfESkyAttr 234 pfESkyColor 234 pfESkyFog 234 pfESkyMode 234 476 pfExpQuat 405 pfFeature 456 466 pfFilePath 65 393 pfFindFile 393 pfFlatten 126 221 261 451 454 462 464 pfFlattenString 332 pfFlushState 360 pfFogRange 351 pfFogType 350 pfFontAttr 329 pfFontCharGSet 329 pfFontCharSpacing 329 pfFontMode 329 pfFrame 65 79 85 157 158 174 177 193 217 220 228 391 428 452 481 pfFrameRate 192 193 427 pfFree 386 387 pfFrustContainsBox 413 pfFrustContainsCyl 413 pfFrustContainsPt 412 pfFrustContainsSphere 413 pfFSatsClass 436 pfFStatsAttr 442 pfFStatsClass 433 439 pfFStatsCountNode 436 438 pfFullXformPt3 398 pfGetArena 387 pfGetBboardAxis 141 pfGetBboardMode 141 pfGetBboardPos 141 pfGetChanFStats 425 436 pfGetChanLoad 194 pfGetChanView 97 pfGetChanViewMat 97 pfGetChanViewOffsets 97 pfGetCullResult 173 pfGetCurGState 361 pfGetCurWSConnection 371 374 pfGetDC
56. pipelines functional stages 73 multiple 217 385 multiprocessing 174 overview 73 setting up 63 pipe windows 79 pitch 95 defined 524 pixie 467 pixie 467 plant walkthroughs xxv point lights See light points 32 point volume intersection tests 412 Polya George xxxiii POLY format See formats poor programming practices array allocation of pfObjects 486 popping definition 524 in LOD transitions 207 porting graphics library calls 40 positive rotation 96 Pravata Todd R 300 precision clocks 34 previous statistics 443 See also statistics pr h header file 61 primitives attributes 325 connectivity 323 flat shaded 322 types 321 printing 31 process callbacks 174 defined 524 processor isolation 457 process priority 457 prof 467 profiling glprof 469 prof 467 program counter sampling 467 projective texture 26 242 defined 525 prune definition 525 pruning nodes 159 PTU format See formats public structs 482 punch through definition 525 Q quaternion 404 references Xxix spherical linear interpolation 404 use in C API 482 R radiosity 499 rapid rendering for on air broadcast xxv REACT 457 467 read 391 Reality Engine 24 Reality Engine graphics xxv pipelines multiple 217 547 Index tuning 476 478 real time programming 457 reference count definition 525 reference counting 46 references circular See circular references reflections 25
57. promotion of floating point expressions to double precision can decrease performance for some numerically intensive applications 2 Because cckr doesn t allow a macro to have the same name as a routine the type casting macros in pf h are not available Thus when you pass a pointer to a derived type such as pfGroup or pfGeode to a routine that takes a generic type such as a pfNode that argument must be cast to a pfNode explicitly as shown in the following example pfGeode geode pfSwitch switch pfAddChild pfGroup switch pfNode geode MIPS 3 MIPS 4 and 64 Bit Compilation If you are running version 6 2 or later of IRIX you can compile and execute OpenGL based IRIS Performer applications in 64 bit mode To do this you need to have installed the optional 64 bit versions of the IRIS Performer libraries All that is required then is to use the 64 switch to the compiler This selects the compilation mode and causes libraries to be searched for in usr lib64 instead of usr lib 69 Chapter 3 Building a Visual Simulation Application 70 The 64 bit version of IRIS Performer is itself created using mips3 so that you can compile an application using either the MIPS 3 or MIPS 4 instruction set MIPS 3 executables can run on R4400 based machines such as Onyx and Indigo2 as well as on R8000 based machines such as PowerOnyx and PowerIndigo2 MIPS 4 executables can only be run on R8000 based and subsequent ma
58. simply the file extension string Examples of several complete loader function names are shown in Table 9 3 Table 9 3 Loader Name Composition File Extension Loader Function Name dwb pfdLoadFile_dwb flt pfdLoadFile_flt medit pfdLoadFile_medit obj pfdLoadFile_obj Several shell environment variables are used in the loader location process These are PFLD_LIBRARY_PATH LD_LIBRARY_PATH and PFHOME Confusion about loader locations can be resolved by consulting the sources mentioned above to understand the use of these directory lists and reading the following section Database Loading Details on page 254 When the pfNotifyLevel is set to PFNFY_DEBUG or greater the DSO and loader function names are printed as database are loaded as is the name of each directory that is searched for the DSO The IRIS Performer sample programs including perfly use pfdLoadFile for database importing This allows them to simultaneously load and display databases in many disparate formats As you develop your own database loaders follow the source code examples in any of the libpfdb loaders Then you will be able to load your data into any IRIS Performer application You will not need to rebuild perfly or other applications to view your databases Database Loading Details Details about the database loading process are described further in this section the pfdLoadFile reference page and the source code which is in usr share Performer src li
59. tree node rather than arranged spatially Figure 6 3 shows a sample database represented by cubes cones pyramids and spheres Organizing this database spatially rather than by object type promotes efficient culling This type of spatial organization is the most effective control you have over efficient traversal Cull Traversal yp a o wG op O wy Figure 6 3 How to Partition a Database for Maximum Efficiency 165 Chapter 6 Database Traversal 166 When modeling a database you should consider other trade offs as well Small amounts of geometry in each culling unit whether pfGeode or pfGeoSet provide better culling resolution and result in sending less non visible geometry to the pipeline Small pieces also improve the performance of line segment intersection inquiries see Database Concerns in Chapter 13 However using many small pieces of geometry can increase the traversal time and can also reduce drawing performance The optimal amount of geometry to place in each pfGeoSet depends on the application database system CPU and graphics hardware Custom Visibility Culling Existence within the frustum isn t the only criterion that determines an object s visibility The item may be too distant to be seen from the viewpoint or it may be obscured by other objects between it and the viewer such as a wall or a hill Atmospheric conditions can also affect object visibility An object that is normally visibl
60. usual solution is to use hardware spin locks so that a process can lock the data segment while reading or writing data If all processes must acquire the lock before accessing the data then a process is guaranteed that no other processes will be accessing the data at the same time All processes must adhere to this locking protocol however or exclusion isn t guaranteed In addition to a shared memory arena pfInit creates a semaphore arena whose handle is returned by pfGetSemaArena Locks can be allocated from this semaphore arena by usnewlock and can be set and unset by ussetlock and usunsetlock respectively pfDataPools pfDataPools named shared memory arenas with named allocation blocks provide a complete solution to the memory visibility and memory exclusion problems thereby obviating the need to set global pointers between pfInit and pfConfig For more information about pfDataPools see Datapools on page 388 227 Chapter 7 Frame and Load Control 228 Passthrough Data The techniques discussed thus far don t solve the memory synchronization problem Performer s libpf library provides a solution in the form of passthrough data When using pipelined multiprocessing data must be passed through the processing pipeline so that data modifications reach the appropriate pipeline stage at the appropriate time Passthrough data is implemented by allocating a data buffer for each stage in the processin
61. windows in X applications If for example you want to put your rendering window inside a larger Motif window you will need an X window Libpr provides utilities to shield you from the differences between the different types of windows and guide you in your dealings with the window system Applications that use the IRIS Performer window utilities can be completely portable between IRIS GL and OpenGL and sill have the option of using pure IRIS GL windows if desired when running in IRIS GL You ll be able to use your windows in X applications or direct your rendering to a pre created window The libpr windowing support centers around the pfWindow pfWindows are structures for managing any of the different kinds of windows and associated pfState pfWindows provide an efficient windowing interface between your application and the window system pfWindows shield you from the functional and performance differences between the different graphics libraries and the different window system interfaces and allow you to configure manipulate and query IRIS GL IRIS GL mixed model GLX and OpenGL X windows through a GL and window system independent interface pfWindows also keep track of your graphics state they include a pfState which is automatically initialized when you open a window and switched for you when you change windows IRIS Performer will automatically configure and initialize your window so that it will be ready to start rendering efficientl
62. 0 pipe pfGetPipe 0 pwin pfNewPWin pipe Set the configuration function for the pfPipeWindow pfPWinConfigFunc pwin OpenPipeWindow Indicate that OpenPipeWindow should be called in the draw process upon next call to pfFrame ey pfConfigPWin pwin trigger OpenPipeWindow to be called in the draw process pfFrame while SimDone Initialize graphics state in the draw process void OpenPipeWindow pfPipeWindow pw 86 pfLightModel 1m Set some configuration stuff pfPWinOriginSize pw 0 0 500 500 Open the window will give us initialized libpr and graphics state ap pfOpenPWin pw Shadows require a 32 bit non multisampled zbuffer do zbsize 32 stensize 1 mssize numSamples 32 1 gconfig Using pfPipeWindows numSamples gt gt 1 while PF_ABS getgconfig GC_BITS_ZBUFFER lt 32 amp amp numSamples gt 0 if numSamples gt 0 multisample 1 else RGBsize 12 mssize 0 0 0 zbsize 32 stensize l gconfig multisample 0 set up Local Light Model to go with shadows lm pfNewLModel NULL pfLModelLocal lm 1 pfApplyLModel 1m Notice how in Example 4 4 the functions pfPWinOriginSize and pfOpenPWin are now called in the draw process as opposed to the application process as in Example 4 2 In general configuring or editing any libpf object must be
63. 0f 1 0f 1 0f 0 5f libpr Sample Code snorms pfVec3 pfMalloc 6 sizeof pfVec3 arena pfSetVec3 snorms 0 0 0f 0 0f 1 0f pfSetVec3 snorms 1 0 0f 0 0f 1 0f pfSetVec3 snorms 2 0 0f 1 0f 0 0f pfSetVec3 snorms 3 0 0f 1 0f 0 0f pfSetVec3 snorms 4 1 0f 0 0f 0 0f pfSetVec3 snorms 5 1 0f 0 0f 0 0f scoords pfVec3 pfMalloc 8 sizeof pfVec3 arena pfSetVec3 scoords 0 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 1 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 2 CUBE_SIZE CUBE_SIZE CUBE_SIZE j pfSetVec3 scoords 3 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 4 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 5 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 6 CUBE_SIZE CUBE_SIZE CUBE_SIZE pfSetVec3 scoords 7 CUBE_SIZE CUBE_SIZE CUBE_SIZE nindex ushort pfMalloc 6 sizeof ushort arena nindex 0 0 nindex 1 5 nindex 2 1 nindex 3 4 nindex 4 2 nindex 5 3 vindex ushort pfMalloc 24 sizeof ushort arena vindex 0 0 vindex 1 1 front vindex 2 2 vindex 3 3 vindex 4 0 vindex 5 3 left vindex 6 7 vindex 7 4 vindex 8 4 vindex 9 7 back vindex
64. 1 H else if SharedFlags gt glObject DRAW_GL_OBJECT callobj 1 OpenGL glCallList else if SharedFlags gt glObject PERF_DRAW pfDraw Graphics and Modeling Techniques to Improve Performances On machines with fast texture mapping texture should be used to replace complex geometry Complex objects such as trees signs and building fronts can be effectively and efficiently represented by textured images on single polygons in combination with applying pfAlphaFunc to remove parts of the polygon that don t appear in the image Using texture to reduce polygonal complexity can often give both an improved picture and improved performance This is because e The image texture provides scene complexity and the texture hardware handles scaling of the image with MIP map interpolation functions for minification and on RealityEngine systems Sharpen and DetailTexture functions for magnification e Using just a few textured polygons rather than a complex model containing many individual polygons reduces system load In order to represent a tree or other 3D object as a single textured polygon IRIS Performer can rotate polygons to always face the eyepoint An object of 465 Chapter 13 Performance Tuning and Debugging 466 this type is known as a billboard and is represented by a pfBillboard node As the viewer moves around the object the textured polygon rotates so that the object app
65. 1 62 3x 62 3 12 1 222 ris e m M 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Strip Lengths State shade 12 materials 59 lights 2 inf 1 local 0 light models O twoSided O localViewer 0 textures 2 qetatieda 0 sharpened O detailTextures 0 texEnvs 9 aL endeds Texture Loads ug lpade 000 bytes 0 000 total loads 0 000 b decals 21 transp 0 fog 0 fogRamps ue gstates 60 gsindexes 0 push 2 pop 2 flush 2 basic 0 orm matrix push 3 pop 3 load O mult 3 alz 1 sets 0 Modes Uis ible Bboards o Bb S Ds Groups La yers bleh ee Lpoint Nodes O omni 0 un i Lpoints O omni O uni O bi SCSs 0 DCSs 3 LightSources 1 Evaluated Nodes a Nodes 0 Cull Total Nodes a Seq it c LODs 1 fade c Switches 0 LightSources 1 Cull Nodes Total 115 Tested Reject 0 Trivial accept 115 Non Trivial Figure 12 2 Other Statistics Classes 431 Chapter 12 Statistics 432 Rendering Statistics Several other classes of statistics can be shown each representing a different aspect of rendering performance Some of these classes show Data about visible geometry including a histogram showing the percentage of triangles in the scene that are part of strips of a given length from 1 to 14 Quads are counted as strips of length two independent triangles count as strips of length one This histogram is mostly useful as a diagnostic to see how well your database is structured for drawing effici
66. 25 environment model 32 environment variables DISPLAY 374 LD_LIBRARY_PATH 254 468 PFHOME 254 PFLD_LIBRARY_PATH 254 PFNFYLEVEL 392 PFPATH 65 393 PFTMPDIR 387 PROFDIR 468 SIKPROJ 301 error handling floating point operations 475 notification levels 391 Euler angles 95 defined 516 example code 41 58 142 157 169 205 238 245 251 254 259 343 352 374 376 377 378 381 433 434 443 457 459 460 465 470 491 524 examples 77 83 simple c 55 exceptions floating point 475 exec 474 extending bounding volumes 410 extensibility callback functions 493 subclassing help subclassing objects 490 user data 45 F face culling 339 faces simulating 27 Feiner Steven K xxix field video 427 field of view 93 files formats See formats loading See databases fill statistics 432 See also statistics Fischetti Mark A xxxiv fixed frame rates 191 defined 516 flags compiler 69 flat shaded primitives 322 flat shading 323 flatten definition 516 flattening 31 FLIGHT format See formats flight motion model 6 flight simulation xxxii 16 flimmering 338 516 floating phase definition 517 floating point exceptions 457 475 fog 6 atmospheric effects 233 configuring 350 351 data structures 234 350 enabling 235 performance cost 454 Foley James D xxix forbidden fruit See reserved functions 482 fork 226 474 494 formats 3DS 271 BIN 271 BYU 275
67. 320 pfCopyGState 361 pfCopyMat 401 pfCopyStats 436 437 441 pfCopyVec3 398 pfCreateDPool 388 pfCreateFile 391 pfCrossVec3 398 pfCull 177 216 225 428 pfCullFace 339 449 pfCullPath 168 pfCullResult 172 pfCurCBufferIndex 389 pfCylAroundSegs 410 460 pfCylContainsPt 412 pfdAddExtAlias 255 pfDBase 222 225 pfDBaseFunc 220 452 pfdBldrStateAttr 262 pfdBldrStateMode 262 pfdBldrStateVal 262 pfdCleanTree 261 451 462 464 pfdConverterAttr 255 pfdConverterMode 255 pfdConverterVal 255 pfdConvertFrom 253 pfdConvertTo 253 pfDCSCoord 127 pfDCSMat 127 pfDCSRot 127 pfDCSScale 127 pfDCSTrans 127 549 Index pfdDefaultGState 450 pfDecal 338 358 449 456 517 pfDelete 45 46 47 222 320 328 329 361 387 389 datapools 389 pfDetachChan 105 pfdExitConverter 255 pfdFreezeTransforms 451 462 464 pfdGetConverterAttr 255 pfdGetConverterMode 255 pfdGetConverterVal 255 pfdInitConverter 255 493 pfDisable 224 340 pfDistancePt3 398 pfDivQuat 405 pfdLoadBldrState 262 pfdLoadFile 14 37 59 252 253 254 257 267 393 pfdMakeSceneGState 125 450 pfdMakeSharedScene 125 450 462 pfdOptimizeGStateList 125 450 pfDotVec3 398 pfDPoolAlloc 388 pfDPoolAttachAddr 388 pfDPoolFind 388 pfDPoolLock 389 pfDPoolUnlock 389 pfdPopBldrState 262 pfdPushBldrState 262
68. 9 Importing Databases 294 to have available IRIS Performer provides the function pfdLoadFile_obj to import OBJ files The source code for pfdLoadFile_obj is in the file pfobj c in the usr share Performer src lib libpfdb libpfobj loader source directory The OBJ format database shown in Figure 9 9 models an office building that s part of the Silicon Graphics corporate campus in Mountain View California Figure 9 9 Silicon Graphics Office Building as OBJ Database Files in the OBJ format have a flexible all ASCII structure with simple keywords to direct the parsing of the data This format is best illustrated with a short example that defines a texture mapped square v defines a vertex here are four vertices v 5 000000 5 000000 0 000000 v 5 000000 5 000000 0 000000 v 5 000000 5 000000 0 000000 v 5 000000 5 000000 0 000000 vt defines a vertex texture coordinate four are given Description of Supported Formats vt 0 000000 1 000000 0 000000 vt 0 000000 0 000000 0 000000 vt 1 000000 0 000000 0 000000 vt 1 000000 1 000000 0 000000 usemtl means select the material definition defined by the name MaterialName usemtl MaterialName usemap means select the texturing definition defined by the name TextureNam usemap TextureNam f defines a face This face has four vertices ordered counter clockwise from the upper left in both geometric and
69. A pfLightPoint can contain one or several light points that share common attributes such as color intensity direction and shape The pfLPointState mechanism provides a more comprehensive approach to light point simulation pfLightPoint nodes are retained only for backward compatibility with previous releases of IRIS Performer New applications should use pfLPointStates Table 5 7 describes the functions for working with pfLightPoints Table 5 7 pfLightPoint Functions Function Description pfNewLPoint Create a new pfLightPoint node pfLPointSize Set the size of the points in a node pfGetLPointSize Find out the size of the points in a node pfLPointColor Set the color of a specified point pfGetLPointColor Find out the color of a point pfLPointRot Set the direction and rotation pfGetLPointRot Find out the direction a point is facing Node Types Table 5 7 continued pfLightPoint Functions Function Description pfLPointShape Set the horizontal and vertical envelope pfGetLPointShape Find out the shape of a point pfLPointPos Set the position of each point pfGetLPointPos Find out the position of a point Example 5 7 demonstrates some operations on light points Example 5 7 Setting Up Light Points pfLightPoint lp pfVec4 red pfVec3 pos create a string of ten light points lp pfNewLPoint 10 set the size in screen pixels for each light pfLPointSize lp 1 0f hs set the l
70. By default IRIS Performer tests bounding volumes all the way down to the pfGeoSet level see Chapter 10 libpr Basics to provide fine grained culling However if your application is spending too much time culling you can stop culling at the pfGeode level by calling pfChanTravMode Then if part of a pfGeode is potentially visible all geometry in that pfGeode is drawn without cull testing it first Visibility Culling Example Figure 6 2 portrays a simple database that contains a toy block train and car The block is outside the frustum the bounding volume of the car is partially inside the frustum and the train is completely inside the frustum Cull Traversal Figure 6 2 Sample Database Objects and Bounding Volumes Organizing a Database for Efficient Culling Efficient culling depends on having a database whose hierarchy is organized spatially A good technique is to partition the database into regions called tiles Tiling is also required for database paging Instead of culling the entire database only the tiles that are within the view frustum need to be traversed 163 Chapter 6 Database Traversal 164 The worst case for the cull traversal performance is to have a very flat hierarchy that is a pfScene with all the pfGeodes directly under it and many pfGeoSets in each pfGeode or a hierarchy that is organized by object type for example having all trees in the database grouped under one pine
71. Create Bounding Volumes 410 Routines to Extend Bounding Volumes 410 Routines to Transform Bounding Volumes 411 Testing Points for Inclusion ina Bounding Volume 412 Testing Volume Intersections 413 Intersection Results 413 Available Intersection Tests 417 Discriminator Return Values 418 Corresponding routines in the Cand C API 482 Header Files for libpf Scene Graph Node Classes 483 Header Files for Other libpf Classes 484 Header Files for libpr Graphics Classes 484 Header Files for Other libpr Classes 485 Data and Functions Provided by User Subclasses 491 xxiii Why Use IRIS Performer About This Guide Welcome to the IRIS Performer application development environment IRIS Performer provides a programming interface with ANSI C and C bindings for creating real time graphics applications and offers high performance rendering in an easy to use 3D graphics toolkit IRIS Performer interfaces to both the IRIS Graphics Library also known as IRIS GL and the OpenGL graphics library these libraries combine with the IRIX operating system to form the foundation of a powerful suite of tools and features for creating real time 3D graphics applications on Silicon Graphics systems Use IRIS Performer for building visual simulation applications and virtual reality environments for rapid rendering in on air broadcast and virtual set applications for assembly viewing in large simulation based design tasks or to maximi
72. Database for Efficient Culling in Chapter 6 and Figure 6 3 for examples of the importance of database structure Maintaining a fixed frame rate involves managing future system load by adjusting graphics display actions to compensate for varying past and present loads The theory behind load management and suggested methods for dealing with variable load situations are discussed in the Level of Detail Management section of this chapter 197 Chapter 7 Frame and Load Control Level of Detail Management 198 Sample Code Example 7 1 demonstrates a common approach to frame control The code is based on part of the main c source file used in the perfly sample application Example 7 1 Frame Control Excerpt Set the desired frame rate pfFrameRate ViewState gt frameRate Set the MP synchronization phase pfPhase ViewState gt phase Application main loop while SimDone Sleep until next frame pfsync Should do all latency critical processing between pfSync and pfFrame Such processing usually involves changing the viewing position PreFrame Trigger cull and draw processing for this frame pfFrame Perform non latency critical simulation updates PostFrame All graphics systems have finite capabilities that affect the number of geometric primitives that can be displayed per frame at a specified frame rate Because of these lim
73. Format 281 xix Figures XX Figure 9 5 Figure 9 6 Figure 9 7 Figure 9 8 Figure 9 9 Figure 9 10 Figure 9 11 Figure 9 12 Figure 9 13 Figure 9 14 Figure 10 1 Figure 10 2 Figure 10 3 Figure 10 4 Figure 12 1 Figure 12 2 Figure A 1 Figure A 2 Figure A 3 Figure A 4 Figure A 5 Figure A 6 Figure A 7 Figure A 8 Figure A 9 GFO Database of Mies van der Rohe s German Pavilion 283 Aircar Database in IRIS Inventor Format 286 LSA Format City Hall Database 289 LSB Format Operating Room Database 291 Silicon Graphics Office Building as OBJ Database 294 Plethora of Polyhedra in PHD Format 296 Terrain Database Generated by PTU Tools 298 Model inSGO Format 304 Sample STLA Database 309 Early Automobile in SuperViewer SV Format 311 Primitives and Connectivity 324 pfGeoSet Structure 326 pfGeoState Structure 362 pfCycleBuffer and pfCycleMemory Overview 390 Stage Timing Statistics Display 426 Other Statistics Classes 431 Simulated view of anatrium 499 Another simulated view of the atrium 500 Simulated view of a castle 501 Simulated hallway view 502 Simulated hotel lobby 503 Simulated waiting room 504 Simulated conference room 505 Parliament stairway 506 Unity Temple interior 507 Tables Table 2 1 Table 2 2 Table 4 1 Table 4 2 Table 4 3 Table 5 1 Table 5 2 Table 5 3 Table 5 4 Table 5 5 Table 5 6 Table 5 7 Table 5 8 Table 5 9 Table 5 10 Table 5 11 Table 5 12 Table 6 1 Table 6 2 Table 6 3
74. Image Generation New York John Wiley amp Sons Inc 1983 Reviews the computer image generation process and provides a detailed analysis of early approaches to system design and implementation The bibliography refers to early papers by the designers of the first image generation systems Mathematics of Flight Simulation Stevens Brian L and Frank L Lewis Aircraft Control and Simulation New York John Wiley amp Sons Inc 1992 This book describes the complete implementation of a flight dynamics model for the F 16 fighter aircraft It provides the basic equations of motion and explains how the more complex issues are handled in practice Some source code in FORTRAN is included Bibliography Virtual Reality Kalawsky Roy S Science of Virtual Reality and Virtual Environments Reading Mass Addison Wesley Publishing Company Inc 1993 Geometric Reasoning These two books address geometric reasoning in general rather than any specifically computer related or Performer specific topics e Abbott Edwin A Flatland A Romance of Many Dimensions 6th Ed New York Dover Publications Inc 1952 The story of A Square and his journeys among the dimensions e Polya George How to Solve It A New Aspect of Mathematical Method 2nd Ed Princeton NJ Princeton University Press 1973 Conference Proceedings The proceedings of the I ITSEC Interservice Industry Training Simulation and Education Conference are a prima
75. NULL pfWinOriginSize win 100 100 500 500 pfWinName win Iris Performer pfWinType win PFWIN_TYPE_X pfOpenWin win set up X input event handling on pfWindow Dsp pfGetCurWSConnection xwin pfGetWinWSWindow win XSelectInput Dsp xwin KeyPressMask XMapWindow Dsp xwin XSync Dsp FALSE do_events win static void do_events pfWindow win while 1 while XPending dsp XEvent event XNextEvent Dsp amp event switch event type 377 Chapter 10 libpr Basics libpr Sample Code 378 case Keypress Example 10 12 shows how to make a colored cube This example is derived from source code in usr share Performer src pguide libpr C colorcube c Example 10 12 Constructing a Colored Cube With libpr colorcube c routine for constructing colored cube geoset include lt Performer pr h gt include lt stdlib h gt defineCUBE_SIZE1 0f pfGeoSet MakeColorCube void arena pfGeoSet gset pfGeoState gst pfVec4 scolors pfVec3 snorms scoords ushort nindex vindex cindex Data arrays to be passed to pfGSetAttr should be allocated from heap memory oy scolors pfVec4 pfMalloc 4 sizeof pfVec4 arena pfSetVec4 scolors 0 1 0f 0 0f 0 0f O 5f pfSetVec4 scolors 1 0 0f 1 0f 0 0f O 5f pfSetVec4 scolors 2 0 0f 0 0f 1 0f O 5f pfSetVec4 scolors 3 1
76. PFFONT_NUM_CHARS specify how many characters are in this font PFFONT_RETURN_CHAR specify the index of the character that is considered a return character and thus relevant to line justification pfFontAttr Specify a particular attribute of this pfFont Valid Attributes to set PFFONT_NAME name of this font PFFONT_GSTATE pfGeoState to be used when rendering this font PFFONT_BBOX bounding box that bounds each individual character PFFONT_SPACING Set the overall character spacing if this is a fixed width font also the spacing used if one hasn t been set for a particular character 329 Chapter 10 libpr Basics 330 Example 10 1 Loading Characters into a pfFont Setting up a pfFont pfFont ReadFont void pfFont fnt pfNewFont pfGetSharedArena for i1 0 1i lt numCharacters it t pfGeoSet gset getCharGSet i pfVec3 spacing getCharSpacing i pfFontCharGSet fnt i gset pfFontCharSpacing fnt i spacing pfString Simple rendering of three dimensional text can be done using a pfString A pfString is an array of font indices stored as 8 bit bytes 16 bit shorts or 32 bit integers Each element of the array contains an index to a particular character of a pfFont structure A pfString can not be drawn until it has been associated with a pfFont object via a call to pfStringFont To render a pfString once it references a pfFont call the function
77. Performance How IRIS Performer Helps Performance IRIS Performer uses many techniques to increase application performance Knowing about what IRIS Performer is doing and how it affects the various pipeline stages may help you write more efficient code This section lists some of the things IRIS Performer can do for you Draw Stage and Graphics Pipeline Optimizations During drawing IRIS Performer e Sets up an internal record of what routines and rendering methods are fastest for the current graphics platform This information can be queried in any process with pfQueryFeature You can use this information at run time when setting state properties on your pfGeoStates e Has machine dependent fast options for commands that are very performance sensitive Use the ON and _FAST mode settings whenever possible to get machine dependent high performance defaults Some examples include e pfAntialias PFAA_ON e pfTransparency PFTR_ON e pfDecal PFDECAL_BASE_FAST e pfTexFilter tex filt PFTEX_FAST e pfTevMode tev PFTEV_FAST e Sets up default modes for drawing multiprocessing statistics and other areas that are chosen to provide high scene quality and performance Some rendering defaults differ from GL defaults backface elimination is enabled by default pfCullFace PFCF_BACK and lighting materials use Imcolor in IRIS GL and glColorMaterial in OpenGL to minimize the number of materials required in a database pf MtlColor
78. Performer Helps Performance information about display lists see Display Lists in Chapter 10 for more information about multiprocessing see Successful Multiprocessing With IRIS Performer in Chapter 7 Cull and Intersection Optimizations To help optimize culling and intersection IRIS Performer Provides pfFlatten to resolve instancing via cloning and static matrix transformations by pre transforming the cloned geometry It can be especially important to flatten small pfGeoSets otherwise matrix transformations must be applied to each small pfGeoSet at significant computational expense Note that flattening resolves only static coordinate systems not dynamic ones but that where desired pf DCS nodes can be converted to pfSCS nodes automatically using the IRIS Performer utility function pfdFreezeTransforms which allows for subsequent flattening Using pfFlatten of course increases performance at the cost of greater memory use Further the function pfdCleanTree can be used to remove needless nodes identity matrix pfSCS nodes single child pfGroup nodes and the like Uses bounding spheres around nodes for fast culling the intersection test for spheres is much faster than that for bounding boxes If a node s bounding sphere doesn t intersect the viewing frustum there s no need to descend further into that node There are bounding boxes around pfGeoSets the intersection test is more expensive but provide
79. Token X Window will be an X window as opposed to a pure IRIS GL window This only has effect under IRIS GL operation STATS Window will have framebuffer resources to accommodate hardware statistics modes This type cannot be combined with PFWIN_TYPE_OVERLAY or PFWIN_TYPE_NOPORT 365 Chapter 10 libpr Basics 366 Table 10 19 continued pfWinType Tokens PFWIN_TYPE_ Description Bitmask Token OVERLAY Window will have only overlay planes for rendering This type cannot be combined with PFWIN_TYPE_STATS or PFWIN_TYPE_NOPORT NOPORT Window will have a graphics context but no physical window or graphics or framebuffer rendering resources and will not be placed on the screen This token should not be used in combination with any other type token The selection of screen can be done explicitly with pfWinScreen or implicitly by opening a connection to the window system using pfOpenScreen with the desired screen as the default screen A window system connection can communicate with any screen on the system the default screen only determines the screen for windows that do not have a screen explicitly set for them Only one window system connection should be opened for a process See Communicating with the Window System later in this section for details on efficient interaction with the window system The position and or size is set with pfWinOriginSize If the x and y components of the origin are 1 the w
80. Windowing with pfWindows e Real time clocks and e Memory management with pfMemory pfList pfObject pfDataPool pfCycleMemory and pfCycleBuffer All libpr geometry is defined by modular units that employ a flexible specification method These basic groups of geometric primitives are termed pfGeoSets 319 Chapter 10 libpr Basics 320 Geometry Sets A pfGeoSet is a collection of geometry that shares certain characteristics All items in a pfGeoSet must be of the same primitive type whether they re points lines or triangles and share the same set of attribute bindings you can t specify colors per vertex for some items and colors per primitive for others in the same pfGeoSet A pfGeoSet forms primitives out of lists of attributes that may be either indexed or nonindexed An indexed pfGeoSet uses a list of unsigned short integers to index an attribute list See Attributes on page 325 for information about attributes and bindings Indexing provides a more general mechanism for specifying geometry than hard wired attribute lists and also has the potential for substantial memory savings as a result of shared attributes Nonindexed pfGeoSets are sometimes easier to construct usually a bit faster to render and may save memory since no extra space is needed for index lists in situations where vertex sharing isn t possible A pfGeoSet must be either completely indexed or completely nonindexed it s not legal to h
81. a new operator defined to take additional arguments e g operator new size_t s void arena Attempting to delete an array of objects allocated in this manner can cause unpredictable and fatal results such as the invocation of the destructor a large number of times on pointers inside and outside of the original allocation All objects of classes derived from pfObject or pfMemory are reference counted and must be deleted using pfDelete rather than the delete operator pfDelete checks the reference count of the object and when multiprocessing delays the actual deletion until other processes are done with the object To decrement the reference count and delete with a single call use pfUnrefDelete Public structs such as pfVec3 pfSphere etc may be deleted either with pfDelete or the delete operator Invoking Methods on IRIS Performer Objects Since libpr and libpf objects are allocated they can only be maintained by reference Passing Vectors and Matrices to Other Libraries Passing arrays of floats is very common in graphics programming Calls to IRIS GL or OpenGL often require an array of floats or a matrix In the C API 487 Chapter 14 Programming with C Porting from C API to C API 488 the data types such as pfMatrix are arrays and so can be passed straight through to OpenGL routines e g pfMatrix ident pfMakeIdentMat ident glLoadMatrix ident In the C API the data field of the pfMatrix must b
82. amp pfHalfSpacelIsectSeg hs i seg dl d2 if retval 0 return 0 pfClipSeg seg dl d2 return retval Note that these routines do not actually clip the segment If you want the segment to be clipped to the interior of the volume you must call pfClipSeg as in the example above Intersecting With Planes and Triangles Intersections with planes and triangles are simpler than those with volumes pfPlanelsectSeg and pfTrilsectSeg return either PFIS_TRUE or PFIS_FALSE depending on whether an intersection has occurred The distance of the intersection along the segment is returned in one of the arguments Intersecting With pfGeoSets You can intersect line segments with the drawable geometry that s within pfGeoSets by calling pfGSetIsectSegs The operation is very similar to that of pfNodelsectSegs except that rather than operating on an entire scene graph only the triangles within the pfGeoSet are traversed Creating and Working With Line Segments pfGSetIsectSegs takes a pfSegSet and tests to see whether any of the segments intersect the polygons inside the specified pfGeoSet By default information about the closest intersection along each segment is returned as a set of pfHit objects one for each line segment in the request Each pfHit object indicates the location of the intersection the normal and what element was hit This element identification includes the index of the primitive with
83. and in OpenGL with glFinish These calls are expensive and shouldn t be done more than at the start and end of drawing in frame Displaying Statistics Simply To put up a simple statistics display all you have to do is call the function pfDrawChanStats and pass it a pointer to the pfChannel whose statistics you want to display The pfDrawChanStats routine can be called from any process within the application the statistics will be displayed in the channel specified If you want to display one channel s statistics in another channel call pfDrawFStats for an example of this technique as well as the enabling and disabling of every statistics class see the statistics programming example in the file usr share Performer src pguide libpf C stats c By default a statistics display shows all enabled statistics If you want to show only a subset of the statistics you re collecting call pfChanStatsMode with an enabling bitmask indicating which classes are to be displayed Collecting and Accessing Statistics in Your Application Enabling and Disabling Statistics for a Channel For efficiency you may want to turn off statistics collection for a given channel when you re not displaying that channel s statistics In particular the stage timing statistics are enabled by default so if you re using a channel whose statistics you don t care about you should disable statistics for that channel To turn off statistics for a ch
84. as a detail texture when the terrain is viewed on RealityEngine systems This texture is used in addition to the base texture image An optional detail texture spline table definition The blending of the primary texture image and the secondary detail texture is controlled by a blend table defined by this spline function The spline table is optional even when a detail texture is specified Detail texture and its associated blend functions are applicable only on RealityEngine systems 299 Chapter 9 Importing Databases 300 The source code for the PTU format importer is provided in the file usr share Performer src libflibpfdb libpfptu pfptu c pfdLoadFile uses the function pfdLoadFile_ptu to load PTU format files into IRIS Performer run time data structures SIMNET S1000 Format The 1000 format is used by the United States ARMY SIMNET distributed simulation system for armored vehicle training The IRIS Performer s1k loader is in the usr share Performer srcflibflibpfdb libpfs1k directory It consists of two libraries an IRIS Performer loader library developed by Todd R Pravata of Texas Instruments Inc in Plano Texas and an 1000 data format toolkit that may be requested from the following source Frank Abbruscato Director of Data Support Division Digital Processing Center US Army Topographic Engineering Center 7701 Telegraph Road Alexandria VA 22310 3864 phone 703 355 2954 email fabbrusc tec army mil
85. as detailed in Table 6 6 Table 6 6 Possible Traversal Results Set Bits Meaning PFTRAV_CONT Continue the traversal inside this subgraph or GeoSet PFTRAV_PRUNE Continue the traversal but skip the rest of this subgraph or GeoSet PFTRAV_TERM Terminate the traversal here Line Segment Clipping Usually the intersection point of most interest is the one that is nearest to the beginning of the segment By default after each successful intersection the end of the segment is clipped so that the segment now ends at the intersection point Upon the final return from the traversal it contains the closest intersection point However if you want to examine all intersections along a segment you can use a discriminator callback to tell IRIS Performer not to clip segments simply leave out the PFTRAV_IS_CLIP_END bit in the return value If you want the farthest intersection point you can use PFTRAV_IS_CLIP_START so that after each intersection the new segment starts at the intersection point and extends outward Intersection Traversal Traversing Special Nodes Level of detail nodes are intersected against the model for range zero which is typically the highest level of detail If you want to select a different model you can turn off the intersection mask for the LOD node and place a switch node in parallel having the same parent and children as the LOD and set it to the desired model Sequences and switches intersec
86. as representing a clockwise or counterclockwise rotation with respect to an axis All CCW rotations in IRIS Performer are specified by positive angles and negative angles represent CW rotations shadow map A special texture map created by rendering a scene from the view of a light source and then recording the depth at each pixel This Z map is then used with projective texturing in a second pass to implement cast shadows The entire process is automated by the IRIS Performer pfLightSource node shared instancing The simplest form of instancing whereby two or more parent nodes share the same node as a child In this situation any change made to the child will be seen in each instance of that node Also see cloned instancing shininess The coefficient of specular reflectivity assigned to a pfMaterial that governs the appearance of highlights on geometry to which it is bound siblings The name given to nodes that have the same parent in a scene graph skip Refers to frame processing See drop sorting The grouping together of geometry with similar graphics state for more efficient rendering with fewer graphics state changes IRIS Performer sorts during scene graph traversal spacing The relative motion required to move the starting point for subsequent pfFont rendering after drawing a particular character pfGeoSet in a pfFont This motion is a pfVec3 to allow arbitrary escapement for character sets that use vertical ra
87. be discussed further in the Section Creating and Configuring a pfChannel Example 4 3 pfPipeWindow with alternate configuration windows main pfPipe pipe pfPipeWindow pwin pfiInit pfConfig Create pfPipeWindow for pfPipe 0 pipe pfGetPipe 0 pwin pfNewPWin pipe request automatic default overlay and stats windows pfPWinMode pwin PFWIN_HAS_OVERLAY PF_ON pfPWinMode pwin PFWIN_HAS STATS PF_ON Open the main graphics window pfOpenPWin pwin pfFrame while SimDone if Shared gt winSel PFWIN_STATS_WIN select statistics window and enable fill stats pfPWinIndex Shared gt pw PFWIN_STATS_WIN pfFStatsClass fstats PFSTATSHW_ENGFXPIPE_FILL PFSTATS_ON pfEnableStatsHw PFSTATSHW_ENGFXPIPE_FILL else we are not doing statistics so turn them off pfFStatsClass fstats PFSTATSHW_ENGFXPIPE_FILL PFSTATS OFF pfDisableStatsHw PFSTATSHW_ENGFXPIPE_FILL pfPWinIndex Shared gt pw Shared gt winSel Using pfPipeWindows Channel draw process drawing function void DrawFunc void pfChannel chan pfPipeWindow pwin pwin pfGetChanPWin chan if pfGetPWinIndex pwin los PFWIN_OVERLAY_WIN Draw overlay image DrawOverlay Put back the normal drawing window pfPWinIndex pwin PFWIN_GFX_WIN Indicate that we will now draw to the wi
88. be used to render the object without substantial loss of image quality The overall result is fewer polygons to draw and improved performance 192 Frame Rate Management Multiprocessing and level of detail is discussed in this chapter while view culling and state sorting are discussed in Chapter 6 Database Traversal More information on sorting in the context of performance tuning can be found in Chapter 13 Performance Tuning and Debugging Fixing the Frame Rate Frame intervals are fixed periods of time but frame processing is variable in nature Because things change in a scene such as when objects come into the field of view frame processing cannot be fixed In order to maintain a fixed frame rate the average frame processing time must be less than the frame time so that fluctuations don t exceed the selected frame time Alternately the scene complexity can be automatically reduced or increased so that the frame rate stays within a user defined sweet spot This mechanism requires that the scene be modeled with levels of detail pfLOD nodes Each frame IRIS Performer calculates the system load for each frame Load is calculated as the percentage of the frame period it took to process the frame Then if the default IRIS Performer fixed frame rate mechanisms are enabled load is used to calculate system stress which is in turn used to adjust the level of detail LOD of visible models LOD management is IRIS Pe
89. being used with IRIS Performer libpfEXT_igl so for the optimized IRIS GL loader Developing Custom Importers libpfEXT_igl g so for the debug IRIS GL loader libpfEXT_ogl so for the optimized OpenGL loader libpfEXT_ogl g so for the debug OpenGL loader Look for the DSO in several places including SPFLD_LIBRARY_PATH SLD_LIBRARY_PATH SPFHOME usr lib 32 64 libpfdb SPFHOME usr share Performer lib libpfdb Open the DSO via dlopen e Once the object has been found processing continues Query all libpfdu converter functionality from the symbol table of the DSO using dlsym with function names generated by appending _EXT to the name of the corresponding pfd routine name This symbol dictionary is retained for future use Invoke the converter s initialization function pfdInitConverter_EXT if it exists Developing Custom Importers Having fully described how database converters can be integrated into IRIS Performer and the types of functionality they provide the next undertaking is actually implementing a converter from scratch IRIS Performer 2 0 makes a great effort at allowing the quick and easy development of effective and efficient database converters While creating a new file loader for IRIS Performer isn t inherently difficult it does require a solid understanding of the following issues e The structure and interpretation of the data file to be read e The scene graph concepts and nodes of li
90. bin and sgo respectively Wavefront obj Open Inventor iv the STL stereolithography format and so on If your files are in one or more of these formats the perfly program can be used to view them If you have files in other formats you will need to add an importer for those formats to perfly before you can use it to view your files This is not a difficult or daunting task but it does require an understanding of most of IRIS Performer to be done properly It should not be undertaken until you have completed reading this book When you want to develop such file importing routines refer to Chapter 9 Importing Databases for instructions and a discussion of the provided sample file importers Being a complete application makes perfly a good demonstration for IRIS Performer in action but it is also a large rather complex piece of code A better place to start exploring programming with IRIS Performer is the sample code provided in usr share Performer src sample pguide Under this directory you can find examples for programming many of the features available in each of the libraries that make up IRIS Performer using either C or C Chapter 1 Getting Acquainted With IRIS Performer Going Beyond Visual Simulation Deciding Where to Start 10 In perfly you can view an object or scene from any angle and location from points either inside or outside of the scene This is the part of the visual simulat
91. by outer loop and endloop keywords 3 the endloop keyword Here is an excerpt from nut stla one of the STLA files provided in the IRIS Performer sample data directories These are the first two polygons of a 524 triangle hex nut object facet normal 0 1 0 outer loop vertex 0 180666 7 62 2 70757 vertex 4 78652 7 62 1 76185 vertex 4 436 7 62 0 endloop endfacet facet normal 0 381579 0 921214 0 075915 outer loop vertex 4 48833 7 59833 0 vertex 4 436 7 62 0 vertex 4 78652 7 62 1 76185 endloop endfacet Use this function to import data from STLA format files into IRIS Performer run time data structures pfNode pfdLoadFile_stla char fileName pfdLoadFile_stla searches the current IRIS Performer file path for the file named by the fileName argument and returns a pointer to the pfNode that parents the imported scene graph or NULL if the file isn t readable or doesn t contain recognizable STLA format data Description of Supported Formats SuperViewer SV Format The Super Viewer SV format is one of the several database formats that the I3DM database modeling tool can read and write The I3DM modeler was developed by John Kichury of Silicon Graphics and is provided with IRIS Performer The source code for the SV format importer is in the file pfsv c The passenger vehicle database shown in Figure 9 14 was modeled using I3DM and is stored in the SV database format Figure 9 14 Early Automobile
92. chan pfNewChan pfGetPipe 0 Set the callback routines for the pfChannel pfChanTravFunc chan PFTRAV_CULL CullFunc pfChanTravFunc chan PFTRAV_DRAW DrawFunc Attach the visual database to the channel pfChanScene chan ViewState gt scene Attach the EarthSky model to the channel pfChanESky chan ViewState gt eSky Initialize the near and far clipping planes pfChanNearFar chan ViewState gt near ViewState gt far Vertical FOV is matched to window aspect ratio pfChanFOV chan 45 0f NumChans 1 0f Using Channels Initialize the viewing position and direction pfChanView chan ViewState gt initView xyz ViewState gt initView hpr CULL PROCESS CALLBACK FOR CHANNEL The cull function callback Any work that needs to be done in the cull process should happen in this function t void CullFunc pfChannel chan void data z void static long first 1 if EIrSt if pfGetMultiprocess amp PFMP_FORK_CULL amp amp ViewState gt procLock amp PFMP_FORK_CULL pfuLockDownCull pfGetChanPipe chan first 0 PreCull chan data pfCull Cull to the viewing frustum PostCull chan data DRAW PROCESS CALLBACK FOR CHANNEL The draw function callback Any graphics functionality outside IRIS Performer must be done here I O with pure IRIS GL devic
93. change made to the data in a particular frame is not visible in downstream stages of the pipeline until those stages begin processing that frame Processing of libpf objects are frame accurate because multiple copies of data are retained for the different pipeline stages free running The unconstrained phase relationship of image generation where frame rendering is initiated as soon as the previous frame is complete without consideration of a minimum or maximum frame rate 517 Glossary 518 frustum A truncated pyramid two parallel rectangular faces one smaller than the other and four trapezoidal faces that connect the edges of one rectangular face with the corresponding edges of the other rectangular face Note that it is pronounced as it is spelled and contains only one r despite common a misuse Also the plural of frustum is frusta which does not contain an s gaze vector The Y axis from the eyepoint informally the direction the eye is facing graph A network of nodes connected by arcs An IRIS Performer scene graph is so termed due to its having this form In particular a Performer scene graph must be an acyclic graph See also scene graph graphics context The set of modes and other attributes maintained by IRIS GL or OpenGL in both system software and the hardware graphics pipeline that defines how subsequent geometry is to be rendered It is this information which must be saved and resto
94. components uniformly distributed within the range 0 2 to 0 7 and is fully opaque Side Effects POLY Format The Side Effects software PRISMS database modeler format supports both ASCII and binary forms of the POLY format The IRIS Performer loader for ASCII poly files is located in the usr share Performer src lib libpfdb libpfpoly directory The binary format bpoly loader is located in the directory usr share Performer src libflibpfdb libpfbpoly These formats are equivalent in content and differ only in representation The POLY format is an easy to understand ASCII data representation with the following structure 1 A text line containing the keyword POINTS 2 One text line for each vertex in the file Each line begins with a vertex number followed by a colon followed by the X Y and Z axis coordinates of the vertex optional additional information and a new line character The optional information includes color 273 Chapter 9 Importing Databases 274 specification in the form c R G B A a normal vector of the form nN NX NY NZ or a texture coordinate in the form uv S T where each of the values shown are floating point numbers 3 A text line containing the keyword POLYS 4 One text line for each polygon in the file Each line begins with a polygon number followed by a colon followed by a series of vertex indices optional additional information an optional lt char
95. containing block definition entities 4 ENTITIES section containing entities and block references 5 END OF FILE Within each section are groups of values where each value is defined by a two line pair of tokens The first token is a numeric code indicating how to interpret the information on the next line For example the sequence 10 1 000 20 5 000 30 3 000 defines a start point at the XYZ location 1 5 3 The codes 10 20 and 30 indicate respectively that the primary X Y and Z values follow All data values are retained in a set of numbered registers 10 20 and 30 in this example which allows values to be reused This simple state machine type of run length coding makes DXF files space efficient at the cost of making them harder to interpret pfdLoadFile uses the function pfdLoadFile_dxf to load DXF format files into IRIS Performer run time data structures Several widely available technical books provide full details of this format if you need more information Chief among these are AutoCAD Programming 2nd Edition by Dennis N Jump Windcrest Books 1991 and AutoCAD The Complete Reference Second Edition by Nelson Johnson Osborne McGraw Hill 1991 279 Chapter 9 Importing Databases 280 MultiGen OpenFlight Format The OpenFlight format is a binary format used for input and output by the MultiGen and ModelGen database modeling tools produced by MultiGen It is a comprehensive format that can
96. counter for wrapping This additional process can be suppressed using pfClockMode If IRIS Performer cannot find a fast hardware counter to use it defaults to the time of day clock which typically has a resolution between one and ten milliseconds This clock resolution can be improved by using fast timers See the ftimer 1 reference page for more information on fast timers By default processes forked after the first call to pfInitClock share the same clock and will all see the results of any subsequent pfInitClock All such processes receive the same time Managing Nongraphic System Tasks Unrelated processes can share the same clock by calling pfClockName with a clock name before calling pfInitClock This provides a way to name and reference a clock By default unrelated processes don t share clocks Video Refresh Counter VClock The video refresh counter VClock is a counter that increments once for every vertical retrace interval There is one VClock per system In systems where multiple graphics pipelines are present but not genlocked synchronized see the setmon 3 reference page screen 0 is used as the source for the counter A process can be blocked until a certain count or the count modulo some value usually desired number of video fields per frame is reached Table 10 23 lists and describes the pfVClock routines Table 10 23 pfVClock Routines Function Action pfInitVClock Initialize the cloc
97. database process is totally asynchronous If it exceeds a frame time it does not slow down any rendering or intersection pipelines The DBASE process is intended for asynchronous database management when used with pfBuffer pfBuffer A pfBuffer is a logical buffer which isolates database changes to a single process avoiding disastrous collisions on data from multiple processes In typical use a pfBuffer is created with pfNewBuffer made current with pfSelectBuffer and merged with the main IRIS Performer buffer with Successful Multiprocessing With IRIS Performer pfMergeBuffer While the DBASE process is intended for pfBuffer use other processes forked by the application may also use different pfBuffers in parallel for multithreaded database management By ensuring that only a single process uses a given pfBuffer at a given time and following a few scoping rules discussed below the application can safely and efficiently implement asynchronous database paging A pfNode is said to have buffer scope or be in a particular pfBuffer This is an important concept because it affects what you can do with a given node A newly created node is automatically in the currently active pfBuffer until that pfBuffer is merged using pfMergeBuffer At that instant the pfNode is moved into the main IRIS Performer buffer otherwise known as the application buffer A rule in pfBuffer management is that a process may only access nodes that
98. database processing tools and utilities libpfdb Load convert and store specific database formats libpfutil Additional utility functions Before you can import a database you must create it Some simulation applications create data procedurally for examples of this approach see the Silicon Graphics PHD Format on page 295 or Sierpinski Sponge Format sections of this chapter In most cases however you must create visual databases manually Several software packages are available to help with this task and most such systems facilitate geometric modeling texture creation and interactive specification of colors and material properties 251 Chapter 9 Importing Databases Some advanced systems support level of detail specification animation sequences motion planning for jointed objects automated roadway and terrain generation and other specialized functions libpfdu Utilities for Creation of Efficient Performer Run Time structures 252 There are several layers of support in IRIS Performer for loading 3 D models and 3 D environments into IRIS Performer run time scene graphs In fact IRIS Performer 2 0 contains the new libpfdu library devoted to the import of data into and export of data from IRIS Performer run time structures Note that two database exporters have already been written for the Medit and DWB database formats At the top level of the API IRIS Performer provides a standard set of functions to rea
99. definition 515 Designer s Workbench 15 Design Vision Inc 503 detail texture 465 DeWolff Partnership 290 Diamond A J 288 500 502 506 Digital Architecture 504 directed acyclic graph 30 directional lights 237 See also lighting disable graphics modes 340 discriminator callbacks for intersections 418 displace decaling 338 defined 515 display stereo 103 displaying statistics See statistics display list 355 450 GL display list usage 33 IRIS Performer internal 33 display list mode 323 display lists definition 515 dlopen 253 257 535 Index disym 253 257 documentation IRIS GL references xxx OpenGL references xxx Donald Schmitt and Company 288 500 506 double precision arithmetic 466 DRAW 73 draw mask 170 draw mask definition 515 draw traversals See traversals drive motion model 4 driver training 16 drop definition 515 DSO libpf 13 libpfdu 13 libpfui 14 libpfutil 14 libpr 13 DWB format See formats DXF format See formats dynamic definition 516 dynamic coordinate systems See pfDCS nodes dynamics simulation of xxxii dynamic shared objects 13 defined 516 E earth sky model 93 effects atmospheric enabling 235 elastomeric propulsion system 96 enabling atmospheric effects 235 fog 235 536 graphics modes 340 statistics classes 436 entertainment 13 environmental effects 6 environmental model 93 environment mapping
100. description of available light point sizes on your IRIS hardware pfLPointColor sets the color for a specified light point in the given pfLightPoint node Each light in a pfLightPoint can be turned off by setting its red green and blue values to 0 0 or by setting its alpha value to 0 0 which makes it completely transparent Light points with a color of zero will not be considered for rendering Light Points pfLPointRot and pfLPointShape control the direction and shape of all the lights points in a pfLightPoint The direction of the light points in point is the positive Y axis rotated about the X axis by elev and then rotated about the Z axis by azim Roll affects only the light envelope pfLPointShape is used to set the intensity distribution of the light points their visibility envelope A pfLightPoint can have any one of three envelope shapes omnidirectional unidirectional or bidirectional If a light point is omnidirectional it can be seen from any direction with the same intensity This is the fastest light to process and draw using IRIS Performer Unidirectional and bidirectional lights have an elliptical cone of intensity The intensity falloff from the center of the cone to the edge is exponential and is also set with pfLPointShape pfLPointPos is used to set the position of each light point in a pfLightPoint A runway strobe could be implemented with a pfLightPoint containing a single point and repositioning
101. done in the application process pfPipeWindows must be created in the application process However pfPipeWindows may be configured edited opened and closed in the pfPWinConfigFunc configuration callback which will be called in the draw process Window operations are best done in a configuration callback though they can also be done in the drawing callback for a pfChannel on the window Any function which aspires to directly affect the graphics context must be called in the drawing process Table 4 2 shows which processes application or draw via a configuration function that pfPipeWindow calls can be made from and further detail about these functions can be found in the discussion of pfWindows in Chapter 10 libpr Basics 87 Chapter 4 Setting Up the Display Environment 88 Table 4 2 Processes from which to call main pfPipeWindow functions pfPipeWindow Function Application Process Draw process pfNewPWin pfPWinMode pfPWinIndex pfPWinConfigFunc pfOpenPWin pfClosePWin pfClosePWinGL pfPWinOriginSize pfPWinFullScreen pfGetPWinCurOriginSize pfGetPWinCurScreenOriginSize pfPWinFBConfigAttrs pfChoosePWinFBConfig pfPWinFBConfig pfPWinType pfPWinScreen pfPWinShare pfPWinWSWindow pfPWinWSDrawable pfPWinGLCxt pfQueryWin pfMQueryWin Yes Yes Yes Yes Yes Yes X Yes IRIS GL No Yes No Yes but the pfFBConfig must be
102. efficiently render complex geometry with axial or point symmetry A classic sprite example is a tree which is rendered as a single texture mapped quadrilateral The texture image is of a tree and has an alpha component whose values which etches the tree shape into the quad In this case the sprite transformation rotates the quad around the tree trunk axis so that it always faces the viewer Another example is a puff of smoke which again is a texture mapped quad but is rotated about a point to face the viewer so it appears the same from any viewing angle The pfSprite transformation mechanism supports both these simple examples as well as more complicated ones involving arbitrary 3D geometry A pfSprite is a structure which is manipulated through a procedural interface It is different from attributes like pfTexture and pfMaterial since it affects transformation rather than state related to appearance A pfSprite is activated with pfBeginSprite This enables sprite mode and any pfGeoSet that is drawn before sprite mode is ended with pfEndSprite will be transformed by the pfSprite First the pfGeoSet is translated to the 353 Chapter 10 libpr Basics 354 location specified with pfPositionS prite Then it is rotated either about the sprite position or axis depending on the pfSprite s configuration Note that pfBeginSprite pfPositionSprite and pfEndSprite are display listable and this will be captured by a
103. elements at the time of overriding become fixed and cannot be changed until pfOverride is called again with a value of zero to release the state elements The code fragment in Example 10 5 illustrates the use of pfOverride Example 10 5 Using pfOverride pfTransparency PFTR_OFF pfApplyTex brickTex Transparency will be disabled and only the brick texture will be applied to subsequent geometry pfOverride PFSTATE_TRANSPARENCY PFSTATE_TEXTURE 1 Draw geometry HWH Transparency and texture can now be changed pfOverride PFSTATE_TRANSPARENCY PFSTATE_TEXTURE 0 pfGeoState A pfGeoState encapsulates all the rendering modes values and attributes managed by libpr See Rendering Modes on page 335 Rendering Values on page 340 and Rendering Attributes on page 341 for more information pfGeoStates provide a mechanism for combining state into logical units and define the appearance of geometry For example you can set a brick like texture and a reddish orange material on a pfGeoSet and use it when drawing brick buildings 357 Chapter 10 libpr Basics 358 Local and Global State There are two levels of rendering state local and global A record of both is kept in the current pfState The local state is that defined by the settings of the current pfGeoState The rendering state and attributes of a pfGeoState can be either locall
104. events window manager A special X window system client which handles icons window placement and window borders and titles Index Numbers 3DS format See formats 64 bit compilation 69 A Abbot Edwin A xxxiii Abbruscato Frank 300 accessing GL 334 acreate 386 486 509 activation of traversals 154 active database animation sequences 23 as programming language 20 billboards 23 140 level of detail 23 morphing terrain 26 skeleton 28 total animation 28 active scene graph See application traversal Adams J Alan 302 Advanced Graphics Applications 501 505 affine transformations 402 Ahuja Narendra xxxiv airplane 96 Akeley Kurt xxix alias definition 509 allocating memory See memory alpha function 337 animation 26 128 130 characters 27 pfMorph node 153 sequences 23 skeleton 28 total 28 using quaternions for 404 antialiasing 24 340 APP 73 application areas broadcast video 13 driver training 16 entertainment 13 flight simulation 16 rapid rendering xxv simulation based design xxv virtual reality xxv 13 16 virtual sets xxv visual simulation xxv 13 application buffer 221 defined 509 application development tools 16 application traversal 157 applying pfGeoStates 359 arenas 386 388 defined 509 See also shared memory arithmetic precision of 466 array allocation of pfObjects guaranteed failure 486 531 Index aspect ratio matching 9
105. for speed and easy access Examples include pfMatrix and pfSphere These are referred to as public structs or arrays In order to allow some functions to apply to multiple data types IRIS Performer uses the concept of class inheritance Class inheritance takes advantage of the fact that different data types classes often share attributes For example a pfGroup is a node which can have children A pf DCS Dynamic Coordinate System has the same basic structure as a pfGroup but also defines a transformation to apply to its children in other words the pfDCS data type inherits the attributes of the pfGroup and adds new attributes of its own This means that all functions that accept a pfGroup argument will alternatively accept a pfDCS argument For example pfAddChild takes a pfGroup argument but pfDCS dcs pfNewDCS pfAddChild dcs child appends child to the list of children belonging to dcs Because the C language does not directly express the notion of classes and inheritance arguments to functions must be cast before being passed e g pfAddChild pfGroup dcs pfNode child In the example above no such casting is required because IRIS Performer provides macros that perform the casting when compiling with ANSI C Note however that using automatic casting eliminates type checking the macros will cast anything to the desired type If you make a mistake and pass an unintended data type to a casting macro the
106. for the pfWindow when the window is opened and the current pfState is switched when the current pfWindow changes pfSelectState can be used to efficiently switch a different complete pfState pfLoadState will force the full application of a pfState Pushing and Popping State pfPushState pushes the state stack of the currently active pfState duplicating the top state Subsequent modifications of the state through libpr routines are recorded in the top of stack Consequently a call to pfPopState restores the state elements that were modified after pfPushState The code fragment in Example 10 4 illustrates how to push and pop state Example 10 4 Pushing and Popping Graphics State set state to transparency off and texture brickTex pfTransparency PFTR_OFF pfApplyTex brickTex draw geometry here using original state save old state establish new state pfPushState pfTransparency PFTR_ON pfApplyTex woodTex draw geometry here using new state restore state to transparency off and texture brickTex pfPopState Graphics State State Override pfOverride implements a global override feature for libpr graphics state and attributes pfOverride takes a mask that indicates which state elements to affect and a value specifying whether the elements should be overridden The mask is a bitwise OR of the state tokens listed previously The values of the state
107. frame rate e Free run without phase control but with a limit on the maximum frame rate PFPHASE_LIMIT tells the application to run no faster than a specified rate e Fixed frame rate with floating phase PFPHASE_FPLOAT allows the drawing process to display a new frame using swapbuffers 3G at any time regardless of frame boundaries e Fixed frame rate with locked phase PFPHASE_LOCK requires the draw process to wait for a frame boundary before displaying a new frame Free Running Frame Rate Control The simplest form of frame rate control called free running is to have no control at all This uncontrolled mode draws frames as quickly as the 195 Chapter 7 Frame and Load Control 196 hardware is able to process them In free running mode the frame rate may be 60 Hz in the areas of low database complexity but could drop to a slower rate in views that place greater demand on the system Use pfPhase PFPHASE_FREE_RUN to specify a free running frame rate In applications in which real time graphics provide the majority of visual cues to an observer the variable frame rates produced by the free running mode may be undesirable The variable lag in image update associated with variable frame rate can lead to motion sickness for the simulation participants especially in motion platform based trainers or immersive head mounted displays For these and other reasons it is usually preferable to maintain a steady consistent fram
108. function for the libpf application traversal When overloading a traversal function it is usually desirable to invoke the parent class function in this case pfDCS app It is not currently possible to overload libpf s intersection or culling traversals See libpf Objects and Multiprocessing on page 495 Example 14 4 Overloading the libpf Application Traversal int Rotor app pfTraverser trav if enable pfMatrix mat double now pfGetFrameTimeStamp use delta and renorm for large times prevAngle now prevTime 360 0f frequency if prevAngle gt 360 0f prevAngle 360 0f mat makeRot prevAngle axis 0 axis 1 axis 2 setMat mat prevTime now return pfDCS app trav int 492 Multiprocessing and Shared Memory Rotor needsApp void return TRUE The same behavior could also be implemented in either the C or C IRIS Performer API using a callback function specified with pfNodeTravFuncs Note Classes of pfNodes that need to be visited during the application traversal even in the absence of any application callbacks should define the virtual function needsApp to return TRUE Accessing Parent Class Data Members Accesses to parent class data is made through the functions on the parent class Data members on built in classes should never be accessed directly Multiprocessing and Shared Memory Initializing Shared Memory In general to
109. glprof_object tags that will appear in a glprof trace This method has the disadvantage of turning off sorting which may increase the number of mode changes and also the balance of bottlenecks in the scene because it may change the drawing order However it has the advantage of giving per object drawing statistics and it indicates whether a specific object is fill or transform limited Example 13 2 shows sample code for a traversal that installs and removes the glprof object tags taken from trav c The example demonstrates general user traversal code then uses this traversal to install and remove glprof callbacks This code is simplified from that found in usr src Performer src libfibpfutil trav c Example 13 2 General Traversal void InitMyTraverser MyTraverser trav trav gt preFunc NULL trav gt postFunc NULL trav gt mstack NULL trav gt data NULL trav gt node NULL trav gt depth 0 handle return value for pruning or terminating define PFU_DO_RET _ret switch _ret cs case PFTRAV_PRUNE trav gt node prevNode if needPop pfPopMStack trav gt mstack return PFTRAV_CONT case PFTRAV_TERM trav gt node prevNode if needPop pfPopMStack trav gt mstack return PFTRAV_TERM int MyTraverse pfNode node MyTraverser trav 470 Performance Measurement Tools int i TAG numChild 1 int ret PFTR
110. grasp of graphics programming concepts terms such as texture map and homogeneous coordinate aren t explained in this guide and it will help if you re familiar with at least one of the graphics libraries If you re a newcomer to these topics see the references listed under Bibliography at the end of this introduction and examine the glossary for definitions of terms or usage unique to IRIS Performer On the other hand though you need to know a little about graphics you don t have to be a seasoned C or C programmer a graphics hardware guru or a graphics library virtuoso to use IRIS Performer IRIS Performer puts the engineering expertise behind Silicon Graphics hardware and software at your fingertips so you can minimize your application development time while maximizing the application s performance and visual impact The best way to get started is to turn to Chapter 1 Getting Acquainted With IRIS Performer which takes you on a tour of some demo programs These programs let you see for yourself what IRIS Performer does Even if you aren t developing a visual simulation application you might want to look at the demos to see high performance rendering in action At the end of Chapter 1 you ll find suggestions pointing to possible next steps alternatively you can browse through the summary below to find a topic of interest How to Use This Guide What This Guide Contains This guide is divided
111. i Continue with channel initialization Multiple Channels and Multiple Windows For some interactive applications you may want to be able to dynamically control the configuration of Channels and Windows IRIS Performer allows you to dynamically create open and close windows as described in the previous section pfPipeWindows in Action You can also move channels amongst the windows of the shared parent pfPipe and re order channels within a pfPipeWindow Channels can be appended to the end of a pfPipeWindow channel list with pfAddChan and removed with Using Channels pfRemoveChan A channel can only be attached to one pfPipeWindow no instancing of pfChannels is allowed When a pfChannel is put on a pfPipeWindow it is automatically deleted from its previous pfPipeWindow A channel that is not assigned to a pfPipeWindow is not drawn though it may still be culled You can control and re order the drawing of channels within a pfPipeWindow with the pfInsertChan pwin where chan and pfMoveChan pwin where chan routines Both of these routines do a type of insertion pfInsertChan will add chan to pwin s channel list in front of the channel in the list at location where pfMoveChan will delete chan from it s old location and move it to where in pwin s channel list Using Channel Groups In many multiple channel situations including the examples described in the previous section it is useful fo
112. if you re culling down to the pfGeoSet level that is when PFCULL_GSET is set with pfChanTravMode as well as another item to sort during culling If your pfGeoSets are large on the other hand you should definitely cull down to the pfGeoSet level Be sparing in the use of pfLayers Layers imply that pixels are being filled with geometry that is not visible If fill performance is a concern this should be minimized in the modeling process by cutting layers into their bases when possible However this will produce more polygons which require more transform and host processing so it should only be done if it will not greatly increase database size Make the hierarchy of the database spatially coherent so that culling will be more accurate and geometry that is outside the viewing frustum will not be drawn See Figure 6 3 for an example of a spatially organized database Balancing Cull and Draw Processing with Database Hierarchy Construct your database to minimize the draw process time spent traversing and rendering the culled part of the database without the cull process time becoming the limiting performance factor This process involves making tradeoffs as a simpler cull means a less efficient draw stage This section describes these tradeoffs and some good rules to follow to give you a good start Specific Guidelines for Optimizing Performance If the cull and draw processes are performed in parallel the goal is to minimize
113. in SuperViewer SV Format Within SV files object geometry and attributes are described between text lines that contain the keywords model and endmodel For example model wing geometry and attributes endmodel 311 Chapter 9 Importing Databases 312 Any number of models can appear within a SuperViewer file The geometry and attribute data mentioned above each consist of one of the following types 3D Polygon with vertex normals and optional texture coordinates poly3dn lt num_vertices gt textured xl yl zl nxi nyl nzl sl t1 x2 y2 z2 nx2 ny2 nz2 s2 t2 Where Xn Yn Zn are the nth vertex coordinates Nxn Nyn Nzn are the nth vertex normals Sn Tn are the nth texture coordinates 3D Triangle mesh with vertex normals and optional texture coordinates tmeshn lt num_vertices gt textured xl yl z1 nx1 ny1 nzl s1 t1 x2 y2 z2 nx2 ny2 nz2 s2 t2 Where Xn Yn Zn are the nth vertex coordinates Nxn Nyn Nzn are the nth vertex normals Sn Tn are the nth texture coordinates Material definition If the material directive exists before a model definition it is taken as a new material specification Its format is material n Ar Ag Ab Dr Dg Db Sr Sg Sb Shine Er Eg Eb Where nisan integer specifying a material number Ar Ag Ab is the ambient color Dr Dg Dbis the diffuse color Sr Sg Sb is the specular color Shine is the material shininess Er Eg Eb is the emissive c
114. information on fog parameters and operation 235 Chapter 8 Creating Visual Effects Light Points 236 The earth sky model is an attribute of the channel and thus accesses information about the viewer s position current field of view and other pertinent information directly from pfChannel To set the pfEarthSky in a channel use pfChanESky pfLightPoint Note pfLightPoint nodes have been obsoleted in favor of the libpr attribute pfLPointState described in pfLPointState on page 237 However the pfLightPoint node is still available for convenience A pfLightPoint is a pfNode that contains one or more light points Light points are used in flight simulation applications to simulate runway lighting taxiway lights and street lights The light points in a pfLightPoint node share all attributes except point location A pfLightPoint node can be thought of as representing a string of similar point lights pfNewLPoint creates and returns a handle to a pfLightPoint node pfLPointSize sets the screen size for all points in a pfLightPoint The size is specified in pixels and is used as the argument to the IRIS GL function pntsizef or the OpenGL function glPointSize Whenever possible graphics library antialiased points are used to represent light points but the actual representation depends on the graphics hardware being used See the IRIS GL pntsizef reference page or the OpenGL glPointSize reference page for a
115. instance p pfGetPipe 0 sets p to point to the IRIS Performer graphics pipeline numbered zero IRIS Performer maintains its own representation of the global graphics state Therefore changes that you make to the graphics state using graphics library IRIS GL or OpenGL commands can create inconsistencies IRIS Performer provides state management routines that let you manipulate both the graphics library state and the IRIS Performer state When you want to change graphics states use these routines rather than their graphics library counterparts See Using Pipes in Chapter 4 for more information on configuring graphics on a pipe and Graphics State in Chapter 10 for more information on controlling the graphics state Frame Rate and Synchronization The frame rate is the number of times per second the application intends to draw the scene The period for a frame must be an integer multiple of the video vertical retrace period which is typically 1 60th of a second Thus with a 60 Hz video rate possible frame rates are 60 Hz 30 Hz 20 Hz 15 Hz and so on simple c doesn t specify a frame rate so it attempts to free run at the default rate of 60 Hz The synchronization mode or phase defines how the system behaves if drawing takes more than the requested time Free running mode the default is useful for applications that don t require a fixed frame rate pfSync delays the application until the next appropriate frame
116. is designed to compute accurate simulations of global illumination within complex 3D environments The output files created with Lightscape Visualization can be read into IRIS Performer for real time visual exploration Lightscape Technologies provides importers for two of their database formats the simple ASCII LSA format and the comprehensive binary LSB format These loaders are in the usr share Performer src libflibpfdb libpflsa and libpflsb directories in the files pflsa c and pflsb c Files in the LSA format are in ASCII and have the following components 1 a4x4 view matrix representing a default transformation 2 counts of the number of independent triangles independent quadrilaterals triangle meshes and quadrilateral meshes in the file 3 geometric data definitions 287 Chapter 9 Importing Databases 288 There are four types of geometric definitions in LSA files The formats of these definitions are as shown in Table 9 7 Table 9 7 Geometric Definitions in LSA Files Geometric Type Format Triangle t X1 Y1 Z1 C1 X2 Y2 Z2 C2 X3 Y3 Z3 C3 Triangle mesh tmn X1 Y1 Z1 Cl X2 Y2 Z2 C2 Quadrilateral q X1 Y1 Z1 C1 X2 Y2 Z2 C2 X3 Y3 Z3 C3 X4 Y4 Z4 C4 Quadrilateral mesh qmn X1 Y1 Z1 C1 X2 Y2 Z2 C2 The Cn values in Table 9 7 refer to colors in the format accepted by the IRIS GL function cpack these colors should be provided in decimal form The X Y and Z values are vertex coordinates Polygon vertex ordering in
117. isect if not ALL_IN all half spaces don t know for sure if isect amp PFIS_ALL IN isect amp PFIS_TRUE return isect Creating and Working With Line Segments 414 A pfSeg represents a line segment starting at position pos extending for a distance length in the direction dir typedef struct pfVec3 pos pfVec3 dir float length pfSeg The routines that operate on pfSegs assume that dir is of unit length and that length is positive otherwise the results of operations are undefined You can create line segments in three different ways e Specify a point and a direction directly in the structure pfSeg e Specify two endpoints pfMakePtsSeg Creating and Working With Line Segments e Specify one endpoint and an orientation in polar coordinates pfMakePolarSeg e Specify starting and ending distances along an existing segment pfClipSeg Intersection tests are the most important operations that use line segments You can test the intersection of segments with volumes half spaces spheres and boxes with 2D geometry planes and triangles and with geometry inside pfGeoSets Intersecting With Volumes IRIS Performer supports intersections of segments with three types of convex volumes pfHalfSpacelIsectSeg intersects a segment with the half space defined by a plane with an outward facing normal pfSpherelsectSeg intersects with a sphere and pfBoxIsectSeg intersects
118. it isn t recommended since any modifications to the database will not be visible to the application process if it is separate from the cull as when using PFMP_APP_CULLDRAW or PFMP_APP_CULL_DRAW However for transient modifications like custom level of detail switching it is reasonable for the cull process to modify the database The draw process should never modify any pfNode IRIS Performer graphics routines should be called only from the cull or draw processes These routines may modify hardware graphics state They are the routines which can be captured by an open pfDispList See Display Lists in Chapter 10 If invoked in the cull process these routines are captured by an internal pfDispList and later invoked in the draw process but if they are invoked in the draw process they immediately affect the current window These graphics routines can be roughly partitioned into those that apply a graphics entity pfApplyMtl0 pfApplyTex and pfLightOn enable or disable a graphics mode pfEnable pfDisable set or modify graphics state pfTransparency pfPushState pfMultMatrix draw geometry or modify the screen pfDrawGSet pfDrawString pfClear Graphics library routines should be called only from the draw process Since there is no open display list to capture these commands an open window is required to accept them Successful Multiprocessing With IRIS Performer e Trigger routines sh
119. libpf so pf h Main IRIS Performer library Contains libpf which handles multiprocessed database traversal and rendering and libpr which performs the optimized rendering state control and other functions fundamental to real time graphics libpfdu so pfdu h Library of scene and geometry building tools which greatly facilitate the construction of database loaders and converts Tools include a sophisticated triangle mesher and state sharing for high performance databases 13 Chapter 2 IRIS Performer Basics 14 Table 2 1 continued IRIS Performer Libraries DSO Name Header File Description libpfutil so pfutil h Utility functions library libpfui so pfui h User interface library Note that while this document refers often to the libpr library or libpr objects the library itself does not exist in isolation it has been placed within the libpf library to improve instruction space layout and caching behavior However libpr still provides an implementation and portability abstraction layer that simplifies the following discussions In addition to the core libraries IRIS Performer provides a suite of database loaders in the form of dynamic shared objects Each loader reads data files or streams structured in a particular format and converts it into an IRIS Performer scene graph Loader libraries are named after their corresponding file extension for example the Wavefront obj format loader is found in
120. libpr routines If you use a modeler that has its own database format you can develop a file importer for it by modifying one of the sample importers See Chapter 9 Importing Databases for more information about import routines If you write your own modeler using libpr routines you don t have to convert the data structures for libpf to be able to use them In this case you create a database by using a series of calls to construct geometry in pfGeoSets to define state and texture definitions in pfGeoStates and to construct a scene graph of pfNodes The sample programs in Chapter 10 Setting Up the Basic Elements libpr Basics show how to construct simple geometry The source code for the sample importers demonstrate the construction of more complex scenes Setting the Search Path for Database Files Database files are often scattered about a file system making file loading operations tedious IRIS Performer provides a general mechanism for defining multiple search paths When IRIS Performer attempts to open a file it first tries the name as specified If that fails it begins to search for the file using a search path which specifies where to look for data You can specify a search path using pfFilePath path or with the environment variable PFPATH You can specify any number of directories in this way The search path consists of a colon separated list of absolute or relative path names of the directories whe
121. material in order to optimize rendering performance It also causes transparent geometry to be drawn after opaque geometry for proper transparency effects By default the enabled culling modes are PRCULL_VIEW PFCULL_GSET PFCULL_SORT It is recommended that these modes be enabled unless the cull traversal becomes a significant bottleneck in the processing pipeline In this case try disabling PFCULL_GSET first then PFCULL_SORT Normally a pfChannel s cull traversal pre traverses the scene following all paths from the scene to all pfLightSources in the scene so that light sources can be set up before the normal scene traversal If you with to disable this pre traversal set the PRCULL_IGNORE_LSOURCES cull enable bit but your pfLightSources will not illuminate the scene The PFTRAV_DRAW argument to pfChanTravMode modifies the draw traversal A mode of PFDRAW_ON is the default and will cause the pfChannel to be rendered A mode of PFDRAW_OFF indicates that the pfChannel should not be drawn and essentially turns off the pfChannel pfNode Draw Mask Each node in the database hierarchy can be assigned a mask that dictates whether the node is added to the display list and thereby whether it is drawn This mask is called the draw mask even though it is evaluated in the cull traversal because it tells the cull process whether the node is drawable or not The draw mask of a node is set with pfNodeTravMask The channel also has a draw
122. mode The default characteristics of a pfEarthSky are listed in Table 8 2 Table 8 2 pfEarthSky Attributes Attribute Default Clear method PFES_FAST full screen clear Clear color 0 0 0 0 0 0 Sky top color 0 0 0 0 0 44 Sky bottom color 0 0 0 4 0 7 Ground near color 0 5 0 3 0 0 Atmospheric Effects Table 8 2 continued pfEarthSky Attributes Attribute Default Ground far color 0 4 0 2 0 0 Horizon color 0 8 0 8 1 0 Ground fog NULL no fog General visibility NULL no fog Cloud top 20000 0 Cloud bottom 20000 0 Cloud bottom color 0 8 0 8 0 8 Cloud top color 0 8 0 8 0 8 Transition zone bottom 15000 0 Transition zone top 25000 0 Ground height 0 Horizon angle 10 degrees By default an earth sky model isn t drawn Instead the channel is simply cleared to black and the Z buffer is set to its maximum value This default action also disables all other atmospheric attributes To enable atmospheric effects select PFES_ SKY PFES SKY GRND or PFES SKY CLEAR when turning on the earth sky model Clouds are disabled when the cloud top is less than or equal to the cloud bottom Cloud transition zones are disabled when clouds are disabled Fog is enabled when either the general or ground fog is set to a valid pfFog If ground fog isn t enabled no ground fog layer will be present and fog will be used to support general visibility Setting a fog attribute to NULL disables it See Fog on page 350 for further
123. mode field If only a rough volume volume intersection is required you can specify a bounding cylinder in the pfSegSet without any line segments at all and request discriminator callbacks at the PFTRAV_IS_NODE or PFTRAV_IS_GSET level Intersection Traversal Figure 6 4 illustrates some aspects of this process The portion of the figure labeled A represents a single segment B is a collection of nonparallel segments not suitable for tightly bounding with a cylinder and C shows parallel segments surrounded by a bounding cylinder In the bottom portion of the figure the bounding cylinder around the segments intersects the bounding box around the object each segment in the cylinder thus must be tested individually to see if any of them intersect Figure 6 4 Intersection Methods 187 Chapter 7 Frame and Load Control This chapter explains how to control frame rate synchronization and dynamic load management Chapter 7 Frame Rate Management Frame and Load Control This chapter describes how to manage the display operations of a visual simulation application to maintain the desired frame rate and visual performance level In addition this chapter covers advanced topics including multiprocessing and shared memory management A frame is the period of time in which all processing must be completed before updating the display with a new image for example a frame rate of 60Hz means the display is updated 60 time
124. multiprocess configuration 75 node callback functions 171 nodes 111 overview of chapter contents xxvii performance tuning 447 pipes 73 sample code 9 sample programs explained 55 scene graphs 155 scene graph structure 163 shadows 242 shared memory 385 spotlights 242 traversals 153 understanding process models 218 understanding statistics 426 using libpr 317 using the C API 70 viewports 93 view specification 97 where to start xxv windows 76 79 writing a loader 259 help compiler flags 69 help process callback functions 174 Henke Joe 504 high resolution clocks 34 384 Hoffman Wes xxix home page xxxv Hughes John F xxix Hume Andrew 295 539 Index I3DM modeler 311 identity matrix definition 519 I ITSEC xxxiii illegal C object creation examples 487 image computation rate 63 IMAGE Society xxxiv IM format See formats immediate mode 323 immediate mode rendering definition 519 Impact xxv importing databases See databases include files 61 483 indexed pfGeoSets 320 Indigo2 Impact xxv industrial simulation xxv INF infinite value exception 475 info performer xxxv inheriting attributes 112 classes 42 state 156 initializing C virtual functions 493 IRIS Performer See pfInit multiprocessing 62 pflype system 493 shared memory 62 in lining math functions 466 input handling 459 460 inset views 102 installing IRIS Performer 3 instancing 120 clone
125. names in two ways the PFPATH environment variable and pfFilePath Note that the PFPATH environment variable controls file search paths and has nothing to do with the pfPath data structure Table 10 27 describes the routines for working with pfFilePaths Table 10 27 pfFilePath Routines Routine Action pfFilePath Create a search path pfFindFile Search for the file using the search path pfGetFilePath Supply current search path Pass a search path to pfFilePath in the form of a colon separated list of path names Calling pfFilePath a second time replaces the current path list rather than appending to it The environment variable PFPATH is also a colon separated list of path names similar to the PATH variable pfFindFile searches the paths in PFPATH first then those given in the most recent pfFilePath call it returns the complete pathname for the file if the file is found IRIS Performer applications should use pfFindFile either directly or through routines such as pfdLoadFile to look for input data files pfGetFilePath returns the last search path specified by a pfFilePath call It doesn t return the path specified by the PFPATH environment variable if you want to find out that value call getenv 3c 393 Chapter 11 Math Routines This chapter details IRIS Performer s comprehensive set of mathematical functions Chapter 11 Vector Operations Math Routines This chapter
126. need not call pfCBufferConfig or pfCBufferFrame since the libpf routines pfConfig and pfFrame call these respectively Asynchronous I O A nonblocking file interface is provided to allow real time programs access to disk files without affecting program timing The system calls pfOpenFile pfCloseFile pfReadFile and pfWriteFile work in an identical fashion to their IRIX counterparts open close read and write When pfOpenFile or pfCreateFile is called a new process is created using sproc which manages access to the file Subsequent calls to pfReadFile pfWriteFile and pfSeekFile place commands in a queue for the file manager to execute and return immediately To determine the status of a file operation call pfGetFileStatus Error Handling and Notification IRIS Performer provides a general method for handling errors both within IRIS Performer and in the application Applications can control error handling by installing their own error handling functions You can also control the level of importance of an error 391 Chapter 10 libpr Basics 392 Table 10 25 lists and describes the functions for setting notification levels Table 10 25 pfNotify Functions Function Action pfNotifyHandler Install user error handling function pfNotifyLevel Set the error notification level pfNotify Generate a notification pfNotify allows an application to signal an error or print a messag
127. node is derived from pfGroup then recursively traverse its children if pfIsOfType node pfGetGroupClassType for i 0 i lt pfGetNumChildren node i travGraph pfGetChild node i Because IRIS Performer allows subclassing of built in types when decisions are made based on the type of an object it is usually better to use pflsOfType to test the type of an object rather than to test for the strict pfObjects and the Class Hierarchy equality of the pflypes Otherwise the code will not have reasonable default behavior with file loaders or applications which use subclassing While the pfType returned from pfGetType is useful to programs it doesn t mean much to humans pfGetTypeName returns a null terminated ASCII string that clearly identifies an object s type For a pfDCS for instance pfGetTypeName returns the string pfDCS 51 Chapter 3 d Building a Visual Simulation This chapter outlines the structure of a simple visual simulation Application application Chapter 3 Overview Building a Visual Simulation Application This chapter outlines the steps involved in using libpf the visual simulation development library The outline follows the development sequence of a skeleton application program that introduces you to the basic concepts involved in creating a visual simulation application with libpf Each step at which more complex constructions are possible gives a cros
128. not supported and IRIS Performer defaults to the PFMP_APP_CULL_DRAW multiprocessing configuration Regardless of the number of pfPipes there is always a single application process which triggers the rendering of all pipes with pfFrame Multithreading For additional multiprocessing and attendant increased throughput the CULL stage of the rendering pipeline may be multithreaded Multithreading means that a single pipeline stage is split into multiple processes or threads which concurrently work on the same frame Use pfMultithread to allocate a number of threads for the cull stage of a particular rendering pipeline Cull multithreading takes place on a per pfChannel basis that is each thread does all the culling work for a given pfChannel Thus an application with only a single channel will not benefit from multithreading the cull and an application with multiple equally complex channels will benefit most by allocating a number of cull threads equal to the number of channels 217 Chapter 7 Frame and Load Control 218 However it is legal to allocate fewer cull threads if you do not have enough CPUs in this case the threads are assigned to channels on a need basis Order of Calls The multiprocessing model set by pfMultiprocess is used for each of the rendering pipelines In programs that configures the application stage as a separate process all IRIS Performer calls must be made from the process that calls pfConfig
129. of C is decremented Example 2 1 demonstrates how reference counts are incremented and decremented Example 2 1 Objects and Reference Counts pfGeoState gstateA gstateC pfGeoSet gsetB Attach gstateC to gsetB Reference count of gstateC is incremented pfGSetGState gsetB gstateC Attach gstateA to gsetB replacing gstateC Reference count of gstateC is decremented and that of gstateA is incremented pfGSetGState gsetB gstateA This automatic reference counting done by IRIS Performer routines is usually all you ll ever need However the routines pfRef pfUnref and pfGetRef allow you to increment decrement and retrieve the reference count of a libpr object should you wish to do so These routines also work with objects allocated by pfMalloc see Memory Allocation in Chapter 10 for more information An object whose reference count is less than or equal to 0 can be deleted with pfDelete pfDelete works for all libpr objects and all pfNodes but not for other libpf objects like pfPipe and pfChannel pfDelete first checks the reference count of an object If the reference count is non positive pfDelete decrements the reference count of all objects that the current object references then it deletes the current object pfDelete doesn t stop here but continues down all reference chains deleting objects until it finds one whose count is greater than zero Once all referenc
130. of gset is incremented pfAddGSet geode gset This has no effect since the parent count of geode is 1 pfDelete geode This deletes group geode and gset pfDelete group pfObjects and the Class Hierarchy Some notes about reference counting and pfDelete e All reference count modifications are locked so that they guarantee mutual exclusion when multiprocessing e Objects added to a pfDispList don t have their counts incremented due to performance considerations e Inthe multiprocessing environment of libpf the successful deletion of a pfNode doesn t have immediate effect but is delayed one or more frames until all processes in all processing pipelines are through with the node This accounts for the fact that pfDispLists don t reference count their objects e pfUnrefDelete obj is shorthand for pfUnref obj pfDelete obj e Objects whose count reaches zero are not automatically deleted by IRIS Performer You must specifically request that an object be deleted with pfDelete or pfUnrefDelete Copying Objects with pfCopy pfCopy is currently implemented for libpr and pfMalloc objects only Object references are copied and reference counts are modified appropriately as illustrated in Example 2 4 Example 2 4 Using pfCopy pfGeoState gstate0 gstatel pfMaterial mtlA mt1B gstateO pfNewGState arena gstatel pfNewGState arena mtlA pfNewMtl arena
131. on a specified level of magnification from the corresponding base texture The detail texture can be specified with the pfTexDetail command By default MIPmap levels are generated for the texture automatically OpenGL operation allows for the specification of custom MIPmap levels Both MIPmap levels and detail levels can be specified with pfTexLevel The level number should be a positive number for a minification level and a non positive number for a magnification detail level If you are providing your own minification levels you must provide all log gt MAX texSizeX texSizeY minification levels There is only one detail texture for a pfTexture The magnification filters use spline functions to control their rate of application as a function of magnification and specified level of magnification for detail textures These splines can be specified with pfTexSpline The specification of the spline is a set of control points that are pairs of non decreasing magnification levels specified with non positive numbers and corresponding scaling factors Magnification filters can be applied to all components of a texture only the RGB components of a texture or to just the alpha components OpenGL does not allow different magnification filters between detail and sharpen for RGB and alpha channels Note The specification of detail textures may have GL dependencies and magnifications filters may not be available on all hardware configurations
132. or the results are undefined Both pfMultiprocess pfMultithread and pfMultipipe must be called after pfInit but before pfConfig pfConfig configures IRIS Performer according to the required number of pipelines and the desired multiprocessing and multithreading modes forks the appropriate number of processes and then returns control to the application pfConfig should be called only once during each IRIS Performer application Comparative Structure of Models Figure 7 5 shows timing diagrams for each of the process models The vertical lines are frame boundaries Five frames of the simulation are shown to allow the system to reach steady state operation Boxes represent the functional stages and are labeled as follows An application process for the nth frame Ci cull process for the nth frame Da draw process for the nth frame Only one of these models can be selected at a time but they are shown together so that you can compare their structures Successful Multiprocessing With IRIS Performer CULL DRAW Cc B Host Cull Draw Simulation Process Process Process traversal Period 1 Frame Rate PFMPAPPCULLDRAW C3 D3 C4 D4 i oo C4 PFMPAPPCULL_DRAW D3 es ae PFMP_APP_CULLDRAW PFMP_APP_CULL_DRAW ie PFMP_APP_CULLODRAW Q N N o NS Start Frame 0 Frame 1 Frame 2 Frame 3 Frame 4 Time gt Figure 7 5 Multiprocessing Models 219 Chapter 7 Frame and Loa
133. pfDrawString pfStrings support the notion of flattening to trade off memory for faster processing time This will cause individual non instanced geometry to be used for each character eliminating the cost of translating the text cursor between each character when drawing the pfString Example 10 2 Setting up and drawing a pfString Create a string a rotate it for 2 5 seconds void LoadAndDrawString const char text pfFont myfont ReadMyFont pfString str pfNewString NULL pfMatrix mat float start t Use myfont as the 3 d font for this string pfStringFont str fnt Geometry Center String pfStringMode str PFSTR_JUSTIFY PFSTR_MIDDL GI Color String is Red pfStringColor str 1 0f 0 0f 0 O0f 1 0f Set the text of the string pfStringString str text Obtain a transform matrix to place this string Get TheMatrixToPlaceTheString mat pfStringMat str amp mat optimize for draw time by flattening the transforms pfFlattenString str Twirl text for 2 5 seconds start pfGetTime do pfVec4 clr pfSetVec4 clr 0 0f 0 0f 0 0f 1 0f Clear the screen to black pfClear PFCL_COLOR PFCL_DEPTH clr t pfGetTime start 2 5f t PF_MIN2 t 1 0f pfMakeRotMat mat t 315 0f 1 0f 0 0f 0 0f pfPostRotMat mat mat t 720 0f 0 0f 1 0f 0 0f t t pfPostTransMat mat mat 0 0f 150 08 s
134. pfGeoState is similar to applying each state element individually For example if you set a pfTexture and enable a decal mode on a pfGeoState applying it essentially calls pfApplyTex and pfDecal If in display list mode pfApplyGState is captured by the current display list State is logically pushed before and popped after pfGeoStates are applied so that pfGeoStates don t inherit state from each other This is a very powerful and convenient characteristic since as a result pfGeoStates are order independent and you don t have to worry about one pfGeoState corrupting another The code fragment in Example 10 6 illustrates how pfGeoStates inherit state Example 10 6 Inheriting State gstateA should be textured pfGStateMode gstateA PFSTATE_ENTEXTURE PF_ON gstateB inherits the global textur nable mode pfGStateInherit gstateB PFSTATE_ENTEXTURE Texturing is disabled as the global default pfDisable PFEN_TEXTURE 359 Chapter 10 libpr Basics 360 Texturing is enabled when gstateA is applied pfApplyGState gstateA Draw geometry that will be textured The global textur nable mode of OFF is restored so that gstateB is NOT textured pfApplyGState gstateB Draw geometry that will not be textured The actual pfGeoState pop is a lazy pop that doesn t happen unless a subsequent pfGeoState requires the global
135. pfGetWinWSDrawable 371 pfGetWinWSWindow 371 pfGSetAttr 46 321 325 387 pfGSetBBox 321 pfGSetDrawMode 321 322 323 328 pfGSetGState 46 320 360 pfGSetGStateIndex 320 pfGSetHlight 46 321 351 pfGSetIsectMask 186 321 417 pfGSetlsectSegs 321 328 416 417 418 pfGSetLineWidth 321 pfGSetNumPrims 320 322 pfGSetPntSize 321 pfGSetPrimLengths 320 322 pfGSetPrimType 320 551 Index pfGStateAttr 46 359 361 pfGStateFuncs 361 pfGStatelInherit 359 361 pfGStateMode 336 359 361 pfGStateVal 340 361 pfHalfSpaceContainsBox 413 pfHalfSpaceContainsCyl 413 pfHalfSpaceContainsPt 412 pfHalfSpaceContainsSphere 413 pfHalfSpacelsectSeg 415 pfHlightColor 351 pfHlightLineWidth 351 pfHlightMode 351 pfHlightNormalLength 352 pfHlightPntSize 352 pfHyperpipe 223 pfldleTex 344 pfindex 428 pfinit 59 62 218 226 387 493 494 509 pflnitArenas 386 387 388 494 509 pfInitCBuffer 391 pfInitClock 384 pflnitGfx 82 370 pfinitState 355 356 pfInitVClock 385 pfInsertChan 102 105 pfInsertChild 117 pfInsertGSet 46 138 139 pfinvertAffMat 401 pfiInvertFullMat 401 pfInvertIdentMat 402 pfInvertOrthoMat 401 pfInvertOrthoNMat 401 pfInvertQuat 405 pflsectFunc 217 228 452 pflsLightOn 137 pflsOfType 50 pflsTexLoaded 344 pfLayer 517 pfLayerBase 131 pfLayerDecal 131 5
136. pfQueryWin you must also provide the framebuffer configuration information with pfWinFBConfig and pfWinFBConfigData for OpenGL and GLX respectively pfQueryWin uses the internally stored visual and in the case of GLX the attribute array given to the GLX call GLXlink Table 10 21 Window System Types pfWS Type X Type pfWindow Set Get Routine pfWSWindow Window pfWinWSWindow pfGetWinWSWindow pfWSDrawable Drawable pfWinWSDrawable pfGetWinWSDrawable pfGLContext IRIS GL pfWinGLCxt int pfGetWinGLCxt OpenGL GLXContext pfFBConfig XVisualInfo pfWinFBConfig pfGetWinFBConfig pfWSConnection Display pfGetCurWSConnection 371 Chapter 10 libpr Basics 372 Manipulating a pfWindow Windows are opened with pfOpenWin and closed with pfCloseWin When a window is closed its graphics context is deleted If you have multiple windows you select the window to draw to with pfSelectWin Windows can be dynamically resized with the same sizing commands discussed previously for setting up the window IRIS Performer supports multiple framebuffer configurations for the same drawing area in a GL independent fashion with alternate configuration windows An IRIS Performer alternate configuration window has the same window parent pfWinWSWindow but may have a different drawable and graphics context There are standard alternate configuration windows for overlay and statistics windows that can be automatically c
137. pfStats data structures pfGeode 137 pfGeoSet 320 and bounding volumes 408 compilation 323 connectivity 323 draw modes 322 intersection mask 417 intersections with segments 416 primitive types 321 pfGeoSet data structures adding to pfGeode nodes 46 137 pfGeoState data structures applying 359 attaching to pfGeoSets 360 overview 357 362 pf h header file 61 pfHit 417 pfLayer 131 pfLightPoint 132 pfLightPoint nodes 236 pfLightSource 133 pfLOD nodes 130 pfMatrix 399 pfMatStack 407 546 pfMorph 26 153 PFNFYLEVEL environment variable 392 pfNode 115 119 and bounding volumes 408 pfNode data structures 112 119 attributes 115 operations 116 pfObject data structures 42 51 actual type of 50 pfPartition 144 pfPath data structures 168 PFPATH environment variable 65 393 pfPipe configuration 75 data structures See pipelines pfPlane 409 pfScene nodes 92 pfSCS 126 pfSCS nodes 451 pfSeg 414 and bounding volumes 408 pfSegSet data structure definition 180 intersection with 417 pfSequence 128 pfSphere 408 pfState data structures 355 pfString 330 pfSwitch 127 pfTexEnv data structures See texturing pfTexture data structures See texturing pfVec2 397 pfVec3 397 pfVec4 397 pfWindow functions 41 phase 63 defined 524 PHD format See formats PHIGS 285 Phong shading 25 physics of flight xxxii physiognomy clownish 27 pipe definition 524
138. possibly subsequent lines pfdLoadFile uses the function pfdLoadFile_gds to load gds format files into IRIS Performer Silicon Graphics GFO Format The GFO format is the simple ASCII format of the barcelona database that is provided in the IRIS Performer sample database directory This database represents the famous German Pavilion at the Barcelona Exhibition of 1929 which was designed by Ludwig Mies van der Rohe and is shown in Figure 9 5 Description of Supported Formats Figure 9 5 GFO Database of Mies van der Rohe s German Pavilion The source code for the GFO format loader is provided in the file usr share Performer srcflibflibpfdb libpfefo pfbin c pfdLoadFile uses the function pfdLoadFile_gfo to load GFO format files into IRIS Performer run time data structures When working with GFO files remember that hardware lighting isn t used since all illumination effects have already been accounted for with the ambient color at each vertex The GFO format defines polygons with a color at every vertex It is the output format of an early radiosity system Files in this format have a simple ASCII structure as indicated by the following abbreviated GFO file scope v3f 42 9632 8 7500 0 9374 cpack 0x8785a9 v3f 42 9632 8 0000 0 9374 283 Chapter 9 Importing Databases 284 cpack 0x8785a9 v3f 1 0000 6 5858 10 0000 cpack Oxffffff polygon cpack 0 v3 0 cpack 1 v3f 1 co
139. refresh rate 194 release notes 3 rendering modes 335 multiple channels 100 stages of 214 rendering pipelines definition 525 See pipelines rendering values 340 reserved functions 482 right hand rule 96 right hand rule defined 525 Rogers David F 302 Rohlf John xxix Rolfe J M xxxii roll 95 defined 526 rotating geometry to track eyepoint 140 465 rotations quaternion 404 Rougelot Rodney S xxxii routines pfAccumulateStats 437 pfAddChan 104 pfAddChild 117 221 260 pfAddGSet 46 138 139 pfAddMat 401 pfAddScaledVec3 398 pfAddVec3 398 pfAllocChanData 176 228 458 548 pfAlloclsectData 228 pfAlmostEqualMat 402 pfAlmostEqualVec3 399 pfAlphaFunc 333 337 465 466 pfAlphaFunction 477 pfAntialias 83 340 449 456 481 pfApp 225 pfAppFrame 157 pfApplyCtab 342 350 pfApplyFog 342 pfApplyGState 334 358 359 360 361 pfApplyGStateTable 361 pfApplyHlight 342 351 pfApplyLModel 341 pfApplyLPState 342 pfApplyMtl 224 341 pfApplyTEnv 342 343 pfApplyTex 224 333 341 344 345 358 459 pfApplyTGen 342 347 pfAsynchDelete 222 pfAttachChan 105 pfAttachDPool 388 pfAttachPWin 81 pfAttachWin 372 pfAverageStats 437 pfBboardAxis 141 pfBboardMode 141 pfBboardPos 141 pfBeginSprite 353 354 pfBoxAroundBoxes 410 pfBoxAroundPts 410 pfBoxAroundSpheres 410 pfBoxContainsBox 413 pfBoxConta
140. represent nearly all of IRIS Performer s advanced concepts including object hierarchy instancing level of detail selection light point specification texture mapping and material property specification MultiGen has provided an OpenFlight format importer pfdLoadFile_flt for your use The loaders and associated documentation are in the directories usr share Performer src lib libpfdb libpfflt11 and libpfflt14 Refer to the Readme files in these directories for important information about the loaders and for help in contacting MultiGen for information about pfdLoadFile_flt or the OpenFlight format The image in Figure 9 4 shows a model of a spacecraft created by Viewpoint Animation Engineering using MultiGen This OpenFlight format model was loaded into IRIS Performer using pfdLoadFile_flt Description of Supported Formats Figure 9 4 Spacecraft Model in FLIGHT Format pfdLoadFile uses the function pfdLoadFile_flt to load OpenFlight format files into IRIS Performer run time data structures Files in the OpenFlight format are structured as a linear sequence of records The first few bytes of each record are a header containing an op code the length of the record and possibly an ASCII name for the record The first record in the file is a special database header record whose op code stored as a 2 byte short integer has the value 1 This opcode header can be used to identify OpenFlight format files By convention
141. src pguide libpr C movietex c demonstrates the use of different texture sources for playing texture or video movies on pfGeoSet 343 Chapter 10 libpr Basics 344 screens Changing your image source may cause your texture to go through the formatting stage upon the next pfApplyTex Table 10 11 Texture Image Sources PFTEX_SOURCE_ Token Texture image is take from IMAGE CPU memory location specified by pfTexLoadImage or pfTexImage FRAMEBUFFER framebuffer location offset from window origin as specified by pfTexLoadOrigin VIDEO Sirius video texture drain Texture storage is limited only by virtual memory but for real time applications you must consider the amount of texture storage the graphics hardware supports Textures that don t fit in the graphics subsystem will be paged as needed when pfApplyTex is called Libpr provides routines for managing hardware texture memory so that a real time application does not have to get a surprise texture load pflsTexLoaded called from the drawing process will tell you if the pfTexture is currently properly loaded in texture memory pfIdleTex can be used to free up the hardware texture memory owned by a pfTexture pfLoadTex called from the drawing process can be used to explicitly load a texture into graphics hardware texture memory which will include doing any necessary formatting of the texture image By default pfLoadTex will load the entire tex
142. state to be restored This means that the actual state between pfGeoStates isn t necessarily the global state If a return to global state is required call pfFlushState to restore the global state Any modification to the global state made using libpr functions pfTransparency pfDecal and so on becomes the default global state For best performance set as little local pfGeoState state as possible You can accomplish this by setting global defaults that satisfy the majority of the requirements of the pfGeoStates being drawn By default all pfGeoState state is inherited from the global default pfGeoSets and pfGeoStates There is a special relationship between pfGeoSets and pfGeoStates Together they completely define both geometry and graphics state You can attach a pfGeoState to a pfGeoSet with pfGSetGState to specify the appearance of geometry Whenever the pfGeoSet is drawn with pfDrawGSet the attached pfGeoState is first applied using pfApplyGState This combination of routines allows the application to combine geometry and state in high performance units which are unaffected by rendering order To further increase performance sharing pfGeoStates among pfGeoSets is encouraged Graphics State pfGeoState Routines Table 10 18 lists and describes the pfGeoState routines Table 10 18 pfGeoState Routines Function Description pfNewGState Create a new pfGeoState pfCopy Make a copy of the pfGeoState
143. stored in any supported format see Table 9 6 for a list of supported formats Loading database files with pfdLoadFile is easy The function prototype is pfNode pfdLoadFile char fileName pfdLoadFile tests the filename extension portion of fileName the substring starting at the last period in fileName if any for one of the format name codes listed in Table 9 6 then calls the appropriate importer The file format selection process is implemented using dynamic loading of DSOs which are IRIX Dynamic Shared Objects This process allows new loaders that are developed as database formats change to be used with IRIS Performer based applications without requiring recompilation of the IRIS Performer application The details of the loading process internal to pfdLoadFile include searching for the named file using the current IRIS Performer file path extraction of the file type extension translation of the extension using a registered alias facility formation of the DSO name searching through a list of user defined and standard directories for that DSO dynamic loading of the indicated DSO using dlopen formation of a loader function name finding that function within the DSO using dlsym and finally invocation of the loader function 253 Chapter 9 Importing Databases 254 The loader function name is constructed from two components a prefix and the loader suffix The prefix is always pfdLoadFile_ and the suffix is
144. stripes example the stripes would be the decal geometry There can be multiple layers of decals with successively higher visual priorities See layer geometry depth complexity The pixel rendering load of a frame which is defined as the total number of pixels written divided by the number of pixels in the image For example an image of two full screen polygons would have a depth complexity of 2 It is often observed that different types of simulation images have predictable depth complexities with values ranging from a low of 2 5 for high altitude flight simulation to 4 or more for ground based simulations These figures can serve as a guide when configuring hardware and estimating frame rates for visual simulation systems IRIS Performer fill statistics provide detailed accounting and real time visualization of depth complexity as seen in perfly displace decaling An implementation method for decal geometry that uses a Z displacement to render coplanar geometry The actual displacement used is a combination of a fixed offset and a range based scaled offset which are combined to produce the effective offset display List A list into which graphics commands are placed for efficient traversal Both IRIS Performer and the underlying graphics libraries OpenGL or IRIS GL have their own display list structures draw mask A bit mask specified for both pfNodes and pfChannels which together selects a subset of the scene graph fo
145. such that they would show even less detail than normal In this way LOD states allow biasing among different LODs to maintain desirable rendering speeds while maintaining the visual integrity of various objects depending on their subjective importance rather than solely on their current visual significance In some multichannel applications LOD states are used to control the action of LODs in different viewing channels that have different visual significance criteria for instance one channel might be a normal channel while a second might represent an infra red display Rather than simple use of LOD states it is also possible to specify a list of LOD states to a channel and use indexes from this list for particular LODs via pfChanLODStateList and pfLODLODStateIndex In this way in the normal channel a car s geometry might be particularly important while in the infra red channel the hot exhaust of the same car might be much more important to observe This type of channel dependent LOD can be set up by using two distinct and different LOD states for the same index in the lists of LOD states specified for unique channels 203 Chapter 7 Frame and Load Control 204 Note that because IRIS Performer performs LOD calculations in a range squared space as much as possible for efficiency reasons LOD computation becomes more costly when LOD states contain scales that are not equal to 1 0 or offsets not equal to 0 0 for transitions or
146. test and will not have to write z values to the z buffer or go on to more complex fill operations Use the pfStats fill statistics available for display through the channel statistics to visualize your depth complexity and get a count of how many pixels are being computed each frame Be aware of the cost of any fill operations you use and their relative cost on the relevant graphics hardware configuration Quick experiments you can do to test for a fill limitation include Rendering the scene into a smaller window assuming that doing so will not otherwise affect the scene drawn a non zero pfChannel LOD scale will cause a change in object LODs when you shrink the window Using pfOverride to force the disabling of an expensive fill mode 455 Chapter 13 Performance Tuning and Debugging 456 If either of these tests causes a significant reduction in the time to draw the scene then a significant fill bottleneck probably exists Note Some features may invoke expensive modes that need to be used with caution on some hardware platforms pfAntialias and pfTransparency enable blending if multisampling isn t available Globally enabling these functions on machines without multisampling can produce significant performance degradation due to the use of blending for an entire scene Blending of even opaque objects incurs its full cost pfDecal may invoke stenciling particularly if you have requested the decal mode PFDECAL_
147. texture coordinates Each pair of numbers separated by a slash indicates vertex and texture indices respectively for a polygon vertex f 1 1 2 2 3 3 4 4 pfdLoadFile uses the function pfdLoadFile_obj to load Wavefront OBJ files into IRIS Performer run time data structures Silicon Graphics PHD Format The PHD format was created to describe the geometric polyhedron definitions derived mathematically by Andrew Hume and by the Kaleido program of Zvi Har El This format describes only the geometric shape of polyhedra it provides no specification for color texture or appearance attributes such as specularity The IRIS Performer sample data directories contain numerous polyhedra in the PHD format The image in Figure 9 10 shows many of the polyhedron definitions laboriously computed by Andrew Hume 295 Chapter 9 Importing Databases 296 Figure 9 10 Plethora of Polyhedra in PHD Format The source code for the PHD format importer is in the file usr share Performer src lib libpfdb libpfpoly pfphd c PHD format files have a line structured ASCII form an initial keyword defines the contents of each line of data The file format consists of a filename definition introduced by the keyword file followed by one or more object definitions Object definitions are bracketed by the keywords object begin and object end and contain one or more polygon definitions Objects can have a name in quotes follow
148. that point at regular intervals A rotating beacon could be created using a single point and rotating it each frame using pfLPointRot pfLPointState A pfLPointState is a libpr attribute which when attached to an appropriately configured pfGeoState will cause pfGeoSets of type PFGS_POINTS to be rendered as light points pfLPointStates are intended to obsolete pfLightPoints since they provide a more powerful mechanism for simulating light points Special features of the pfLPointState include e Perspective point size points farther away look smaller than those closer to the eye e Perspective fading points whose computed size is less than an application defined threshold are made more transparent rather than shrinking the point any further e Fog punch through e Directionality including bi directional points with different front and back colors 237 Chapter 8 Creating Visual Effects 238 Since pfLPointState uses the pfGeoState mechanism light points can appear different to different pfChannels by using indexed pfGeoStates and pfGeoState tables For example a light point may look brighter in an infra red channel than in an out the window channel One improvement over pfLightPoints is that point directions are supplied by a pfGeoSet s normals so a single pfLPointState can be used for many light points with differing directions A further improvement is in performance pfLPointStates can use texture mapping to sim
149. that this comfort zone acts as a dead band Instantaneous system load within the bounds of the dead band doesn t result in a change in the system stress level If the size of the comfort zone is too small oscillatory distress is the probable result It is often necessary to keep the highLoad level below the 100 point so that blended LOD transitions don t drive the system into overload situations Successful Multiprocessing With IRIS Performer For those applications in which the default stress function is either inappropriate or insufficient you can compute the system stress yourself and then set the stress load factor Your filter function can access the same system measures that the default stress function uses but it s also free to keep historical data and perform any feedback transfer processing that application specific dynamic load management may require The primary limitation of the default stress function is that it has a reactive rather than predictive nature One of the major advantages of user written stress filters is their ability to predict future stress levels before increased or decreased load situations reach the pipeline Often the simulation application knows for example when a large number of moving models will soon enter the viewing frustum If their presence is anticipated then stress can be artificially increased so that no sudden LOD changes are required as they actually enter the field of view Successful
150. the number of separate data and index arrays Keep the data and index arrays for pfGeoSets contiguous and try to keep separate pfGeoSets contiguous to avoid small fragmented pfMalloc memory allocations The ideal size of a pfGeoSet and of each triangle strip within the pfGeoSet depends a great deal on the specific CPU and system architecture involved you may have to do benchmarks to find out what s best for your machine For a general rule of thumb use at least 4 triangles per strip on any machine and 8 on most Use 5 to 10 strips in each pfGeoSet or a total of 24 to 100 triangles per pfGeoSet 461 Chapter 13 Performance Tuning and Debugging 462 libpf Databases When you re using libpf the following tips can improve the performance of database tasks Use pfFlatten especially when a pfScene contains many small instanced objects and billboards Use pfdCleanTree and if application considerations permit pfdFreezeTransforms to minimize the cull traversal processing time and maximize state sorting scope Initialize each mode in the scene pfGeoState to match the majority of the database in order to set as little local state for individual pfGeoStates as possible The utility function pfdMakeSharedScene provides an easy to use mechanism for this task Minimize the number of very small pfGeoSets that is those containing four or fewer total triangles Each tiny pfGeoSet means another bounding box to test against
151. these files have a flt filename extension pfdLoadFile_flt makes use of several environment variables when locating data and texture files These variables and several additional functions including pfdConverterMode_flt pfdGetConverterMode_flt and pfdConverterAttr_flt assist in OpenFlight file processing 281 Chapter 9 Importing Databases 282 McDonnell Douglas GDS Format The gds format also known as the Things format is used in at least one CAD system and a minimal loader for this format has been developed for IRIS Performer users The IRIS Performer loader for gds files is located in the usr share Performer src lib libpfdb libpfgds directory The GDS format subset accepted by the pfdLoadFile_gds function is easy to describe It consists of the following five sequential sections in an ASCII file 1 The number of vertices which is given following a YIN tag 2 The vertices with one X Y Z triple per line for vertices lines 3 The number zero on a line by itself 4 The number of polygons on a line by itself 5 A series of polygon definitions each of which is represented on two or more lines The first line contains the number one and the name of a material to use for the polygon The next line or lines contain the indices for the polygons vertices The first number on the first line is the number of vertices This is followed by that number of vertex indices on that and
152. three dimension text within the context of libpf pfFont The basic primitive supporting text rendering is the libpr pfFont primitive A pfFont is essentially a collection of pfGeoSets in which each pfGeoSet represents one character of a particular font pfFonts also contain metric data such as a per character spacing the three dimensional escapement offset used to increment a text cursor after the character has been drawn Thus pfFonts maintain all of the information that is necessary to draw any and all valid characters of a font However note that pfFonts are passive and have little functionality on their own for example you cannot draw a Geometry pfFont it simply provides the character set for the next higher level text data object the pfString Table 10 4 lists some routines that are used with a pfFont Table 10 4 pfFont Routines Function Description pfNewFont Create a new pfFont pfDelete Delete a pfFont pfFontCharGSet Set the pfGeoSet to be used for a specific character of this pfFont pfFontCharSpacing Set the 3D spacing to be used to update a text cursor after this character has been rendered pfFontMode Specify a particular mode for this pfFont Valid Modes to set PFFONT_CHAR_SPACING specify whether to use fixed or variable spacings for all characters of a pfFont Possible values are PFFONT_CHAR_SPACING_FIXED and PFFONT_CHAR_SPACING_VARIABLE the latter being the default
153. to place the same model in more than one location by instancing it under more than one pfDCS transformation node intersection pipeline Like the rendering pipeline IRIS Performer supports a two stage multiprocessing pipeline between the APP and ISECT processes See also rendering pipeline latency The amount of time between an input and the response to that input For example rendering latency is usually defined as the time from which the eyepoint is set until the display devices scans out the last pixel of the first field corresponding to that eye point latency critical Operations which must be performed during the current frame and which will reliably finish quickly An example of this would be reading the current position of a head tracking device from shared memory layer geometry Objects that appear above other objects in pfLayer geometry In a runways and stripes example the stripes would be the decal geometry There can be multiple layers of decals with successively higher visual priorities See also base geometry 519 Glossary 520 level of detail The idea of representing a single object such as a house with several different geometric models a cube a simple house and a detailed house for example that are designed for display at different distances The models and ranges are designed such that the viewer is unaware of the substitutions being made This is possible because distant objects appear sma
154. to routines that create data that must be visible to all processes Routines that accept an Successful Multiprocessing With IRIS Performer arena argument are the pfNew routines found in the ibpr library and the IRIS Performer memory allocator pfMalloc In practice it is usually safest to create libpr objects like pfGeoSets and pfMaterials in shared memory libpf objects like pfNodes are always created in shared memory Allocating shared memory does not by itself solve the memory visibility problem discussed above You must also make sure that the pointer that references the memory is visible to all processes IRIS Performer objects once incorporated into the database via routines like pfAddGSet pfAddChild and pfChanScene automatically ensure that the object pointers are visible to all IRIS Performer processes However pointers to application data must be explicitly shared A common way of doing this is to allocate the shared memory after pfInit but before pfConfig and to reference the memory with a global pointer Since the pointer is set before pfConfig forks any processes these processes will all share the pointer s value and can thereby access the same shared memory region However if this pointer value changes in a process its value will not change in any other process since forked processes don t share the same address space Even with data visible to all processes data exclusion is still a problem The
155. transparency levels In addition the flag PFTR_ NO_OCCLUDE may be logically OR ed into the transparency mode in which case geometry will not write depth values into the frame buffer This will prevent it from occluding subsequently rendered geometry Enabling this flag improves the appearance of unordered blended transparent surfaces There are two basic transparency mechanisms screen door transparency which requires hardware multisampling and blending Blending offers very high quality transparency but for proper results requires that transparent surfaces be rendered in back to front order after all opaque geometry has been drawn When using transparent texture maps to etch geometry or if the surface has constant transparency screen door transparency is usually good enough Blended transparency is usually required to avoid banding on surfaces with low transparency gradients like clouds and smoke Shading Model Selects flat shading or Gouraud smooth shading pfShadeModel takes one of two tokens PFSM_FLAT or PFSM_GOURAUD One some graphics hardware flat shading can offer a significant performance advantage Alpha Function pfAlphaFunc is an extension of the IRIS GL function afunction 3g and the OpenGL function glAlphaFunc it allows IRIS Performer to keep track of the hardware mode The alpha function is a pixel test that compares the incoming alpha to a reference value and uses the result to determine whether or
156. usr share Performer src pguide libpf C billboard c Example 5 12 Setting Up a pfBillboard static pfVec2 BBTexCoords 0 0f LOE 7 1 0f 0 0f Oty Of OEF Of Er EY Os O static pfVec3 BBVertCoords 4 XZ plane for pt bboards 0 58 Of 0 0f 0 5f SOE 0f 0252 Of Of 0 5f Of Of om om a PRO Of AE KEA OEF AE A OE OPa E APE LEAL Of world Zup static pfVec3 BBAxes 4 1 0f 0 0f 0 0f 0 0f OL Of Of Of OOF O Be PS a ll A static int BBPrimLens 4 static pfVec4 BBColors 1 0 1 0 1 0 1 0 Convert static data to pfMalloc ed data static void memdup void mem size_t bytes void arena void data pfMalloc bytes arena memcpy data mem bytes return data For pedagogical use only Reasonable performance requires more then one pfGeoSet per pfBillboard oy pfBillboard MakeABill pfVec3 pos pfGeoState gst long bbType pfGeoSet gset pfGeoState gstate pfBillboard bill Node Types void arena pfGetSharedArena j gset pfNewGSet arena gstate pfNewGState arena pfGStateMode gstate PFSTATE_ENLIGHTING PF_OFF pfGStateMode gstate PFSTATE_ENTEXTURE PF_ON Create load texture map for billboard pfGStateAttr gstate PFSTATE_TEXTURE texture pfGSetGState gset gstate pfGSetAttr gset PFGS_C
157. visual simulation xxv 13 overview 19 28 visual simulation origins of xxxii volumes bounding 123 124 boxes 408 creating 410 cylinders 408 460 dynamic 123 extending 410 hierarchical 159 intersection testing 412 spheres 408 visibility testing 162 boxes axially aligned 408 cylinders 409 geometric 408 half spaces 409 intersections See intersections primitives 408 spheres 408 transforming 411 VRML 157 255 285 287 Ww Wavefront 293 OB format 37 widget defined 530 windows 41 76 79 WindRiver 467 WindView 467 wireframe 322 Woo Mason xxx wood balsa 96 WorkShop 467 world s fair 1929 Barcelona Spain 282 Wright Frank Lloyd 507 write 391 www sgi com XXXV X XCreateWindow 371 X windows 91 X window system xxxi 41 Y Yale Compact Star Chart 308 Yellowstone National Park 298 Z z fighting 338 563 Tell Us About This Manual As a user of Silicon Graphics products you can help us to better understand your needs and to improve the quality of our documentation Any information that you provide will be useful Here is a list of suggested topics General impression of the document Omission of material that you expected to find Technical errors Relevance of the material to the job you had to do Quality of the printing and binding Please send the title and part number of the document with your comments The part number for this document is 007 1680
158. whether a node is within a pfChannel s viewing frustum for the current frame Nodes that are not visible are pruned omitted from the list of objects to be drawn so that the Geometry Pipeline doesn t waste time processing primitives that couldn t possibly appear in the final image Hierarchical Bounding Volumes Testing a node for visibility compares the bounding volume of each object in the scene against a viewing frustum that is bounded by the near and far clip planes and the four sides of the viewing pyramid Both nodes see Chapter 5 and pfGeoSets see Chapter 10 have bounding volumes that surround the geometry that they contain Bounding volumes are simple 159 Chapter 6 Database Traversal 160 geometric shapes whose centers and edges are easy to locate Bounding volumes are organized hierarchically so that the bounding volume of a parent encloses the bounding volumes of all its children You can specify bounding volumes or let IRIS Performer generate them for you see Bounding Volumes in Chapter 5 Figure 6 1 shows a frustum and three objects surrounded by bounding boxes Two of the objects are outside the frustum one is within it One of the objects outside the frustum has a bounding box whose edges intersect the frustum as shown by the shaded area The visibility test for this object returns TRUE because its bounding box does intersect the view frustum even though the object itself doesn t Cull Travers
159. with an axially aligned box The intersection test of a segment and a convex volume can have one of five results e The segment lies entirely outside the volume e The segment lies entirely within the volume e The segment lies partially inside the volume with the starting point inside e The segment lies partially inside the volume with the ending point inside e The segment lies partially inside the volume with both endpoints outside As with the volume volume tests the segment volume intersection routines return a value that is the bitwise OR of some combination of the tokens PFIS_TRUE PFIS_ALL_IN PFIS_START_IN and PFIS_MAYBE When PFIS_TRUE is set PFIS_MAYBE is also set for consistency with those routines that do quick intersection tests for culling The functions take two arguments that return the distances along the segment of the starting and ending points The return values are designed so 415 Chapter 11 Math Routines 416 that you can AND them together for testing for the intersection of a segment against the intersection of a number of volumes For example a convex polyhedron is defined as the intersection of a set of half spaces Example 11 4 shows how to intersect a segment with a polyhedron Example 11 4 Intersecting a Segment With a Convex Polyhedron long HSSIsectSeg pfPlane hs pfSeg seg long nhs float dl float d2 long retval Oxffff for long i 0 i lt nhs itt retval
160. your application by gathering statistics on certain operations IRIS Performer provides run time profiling of the time spent in parts of the graphics pipeline for a given frame The pfDrawChanStats function displays application cull and draw time in the form of a graph drawn in a channel see Chapter 12 Statistics for more information on that and related functions There are advanced debugging and tuning tools available from Silicon Graphics that can be of great assistance WorkShop product in the CASEVision tools provides a complete development environment for debugging and tuning of host tasks The Performance Co Pilot helps you to tune host code in a real time environment There is also the Wind View product from WindRiver that works with IRIX REACT to do full system profiling in a real time environment However progress can be made with the basic tools that are in the IRIX development environment prof pixie and glprof The IRIS GL debugging utility gldebug can also be used to aid in performance tuning as can the OpenGL equivalent ogldebug This section briefly discusses getting started with these tools Note See the graphics library manuals available from Silicon Graphics for complete instructions on using these graphics tools See the IRIX System Programming Guide to learn more about pixie and prof Using pixie and prof to Measure Performance You can use the IRIX performance analysis utilities pixie and prof to
161. 0 75 2 25 6 8 20 0 c 18 9342 15 B32 put a disc on the top and bottom of the cylinder d LDiS 3 0 0 L 80 2 di Tb bs 34 00 Tb 0 2 build cylinder cone 00 a2 1S 26 820 0 29 5B 25757 30 put a disc on the bottom of the cone d 20 See 00 Sk 03 build cone sphere 027 200 TS 6 820 0 s 5 15 0 3 build sphere hexahedron E 6252 225 2510 6 4 8 2 0 0 Borg 1S Sf LT ae 2 Description of Supported Formats build hexahedron superquadric sphere f 80 10 30 6 8 20 0 ss 25 V5 0 2 52 21 4 build superquadric_sphere disc washer shape weg ZO e201 DO 46 gt wr8 20 7 0 525 90 02 0112 5 build disc grid height field 80 280 20 26 8 20 0 g 4412 18 22 28 0 4 000 0 OM 0 0 00 10 000 0 build grid superquadric torid E 40 20 60 6 8 20 0 Ste 25 gt 25 0 035 05 5 085 533 23853 build superquadric_torid polygon with no normals f 20 20 20 6 8 20 0 p 4 5 5 gt 0 35 oy SLO 35 35 10 oae a 10 build polygon pfdLoadFile uses the function pfdLoadFile_nff to load NFF format files into IRIS Performer run time data structures Wavefront Technology OBJ Format The OBJ format is an ASCII data representation read and written by the Wavefront Technology Model program A number of database models in this format have been placed in the public domain making this a useful format 293 Chapter
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163. 1 GetNextColorFloat polygon gt colors 0 2 GetNextColorFloat Add this polygon to pfdBuilder Because it is a single poly 1 is specified here pfdAddBldrGeom 1 break case GRAPHICS_STATE_TEXTURE char texName pfTexture tex texName ReadTextureName iimFile if texName NULL Get prototype tex from pfdBuilder 264 Developing Custom Importers tex pfdGetTemplateObject pfGetTexClassType This clears that object to default pfdResetObject tex If just the name of a pfTexture is set pfdBuilder will auto find amp Load the texture pfTexName tex texName This is the current pfdBuilder texture and texturing is on pfdBldrStateAttr PFSTATE_TEXTURE tex pfdBldrStateMode PFSTATE_ENTEXTURE PF_ON else No texture means disable texturing And set current texture to NULL pfdBldrStateMode PFSTATE_ENTEXTURE PF_OFF pfdBldrStateAttr PFSTATE_TEXTURE NULL break case GRAPHICS _STATE_ MATERIAL pfMaterial mtl mtl pfdGetTemplateObject pfGetMtlClassType pfdResetObject mt1 pfMtlColor mtl PE AMBIENT GetAmRed GetAmGreen GetAmBlue pf
164. 1 pfIrilsectSeg 416 pfuCollideSetup 452 pfuDownloadTexList 459 pfuLockDownApp 457 pfuLockDownCull 457 pfuLockDownDraw 457 pfuLockDownProc 457 pfUnref 47 pfUnrefDelete 49 pfUpdatePart 144 145 pfuPrioritizeProcs 457 pfUserData 45 490 pfVClockSync 385 pfViewMat 354 pfWinFBConfig 371 pfWinFBconfig 369 pfWinFBConfigAttrs 368 pfWinFBConfigData 370 371 pfWinFullScreen 80 366 pfWinGLCxt 370 371 pfWinIndex 372 373 pfWinMode 373 pfWinOriginSize 366 pfWinOverlayWin 372 pfWinScreen 366 pfWinShare 372 pfWinStatsWin 372 pfWinType 365 pfWinWSDrawable 370 371 pfWinWSWindow 371 372 373 pfWriteFile 391 pfXformBox 411 pfXformPt3 398 pfXformVec3 398 runway lights 32 Ryan S T airplane 96 555 Index S S1000 data base API 300 S1000 format See formats sample code 9 41 58 77 89 90 91 142 157 169 205 238 245 251 254 259 343 352 374 376 377 378 381 433 434 443 457 459 460 465 470 491 524 sample data 58 sample programs 254 524 perfly 3 sample source directory xxviii sampling program counter 467 scan rate 194 scene definition 526 scene complexity definition 526 scene graph 64 defined 526 state inheritance 156 scene graphs 155 scene hraph 30 Schacter Bruce J xxxii xxxiv screen door transparency 337 SCS See pfSCS nodes search paths 65 393 definition 526 segments
165. 1 0f c 1 0f s pfFrame show objects static for three seconds sleep 3 pfExit exit 0 Oy OE he ALS 8 O O ar gt y 149 Chapter 6 Database Traversal This chapter explains how to manipulate traverse and examine a scene graph Chapter 6 Database Traversal Chapter 5 Nodes and Node Types described the node types used by libpf This chapter describes the operations that can be performed on the run time database defined by a scene graph These operations typically work with part or all of ascene graph and are known as traversals because they traverse the database hierarchy IRIS Performer supports four major kinds of database traversals e Application e Cull e Draw e Intersection The application traversal updates the active elements in the scene graph for the next frame This includes processing active nodes such as pfMorph and invoking user supplied callbacks for animations or other embedded behaviors Visual processing consists of two basic traversals culling and drawing The cull traversal selects the visible portions of the database and puts them into a display list The draw traversal then runs through that display list and sends rendering commands to the Geometry Pipeline Once you have set up all the necessary elements culling and drawing are automatic although you can customize each traversal for special purposes The intersection traversal compute
166. 10 6 vindex 11 5 vindex 12 1 vindex 13 5 right vindex 14 6 vindex 15 2 vindex 16 3 vindex 17 2 top vindex 18 6 vindex 19 7 vindex 20 0 vindex 21 4 bottom vindex 22 5 vindex 23 1 cindex ushort pfMalloc 24 sizeof ushort arena cindex 0 0 cindex 1 alee cindex 2 2 cindex 3 3 cindex 4 0 cindex 5 1 Ccindex 6 2 cindex 7 3 379 Chapter 10 libpr Basics cindex 8 0 cindex 9 1 cindex 10 2 cindex 11 3 cindex 12 0 cindex 13 1 cindex 14 2 cindex 15 3 cindex 16 0 cindex 17 1 cindex 18 2 cindex 19 3 cindex 20 0 cindex 21 1 Ccindex 22 2 cindex 23 3 Allocate the pfGeoSet out of the same arena gset pfNewGSet arena set the coordinate normal and color arrays and their corresponding index arrays Kf pfGSetAttr gset PFGS_COORD3 PFGS_PER_VERTEX scoords vindex pfGSetAttr gset PFGS_NORMAL3 PFGS_PER_PRIM norms nindex pfGSetAttr gset PFGS_COLOR4 PFGS_PER_VERTEX scolors cindex pfGSetPrimType gset PFGS_QUADS pfGSetNumPrims gset 6 Fl ve create a new geostate from shared memory disable texturing and enable transparency i gst pfNewGState arena pfGStateMode gst PFSTATE_ENTEXTURE 0 pfGStateMode gst PFSTATE_TRANSPARENCY 1
167. 3 assembly mock up xxv assignment operators 496 asynchronous database paging definition 509 asynchronous database processing 220 asynchronous deletion 222 asynchronous I O 391 atmospheric effects enabling 235 atmospheric model 32 attribute binding definition 510 attributes bindings 327 461 flat shaded 327 overview 325 traversals 154 AutoCAD 277 automatic type casting 42 average statistics 443 See also statistics axes default 95 axially aligned boxes 408 base geometry 338 definition 510 basic block counting 467 behaviors 157 bezel definition 510 bidirectional lights 237 See also lighting billboards 23 140 466 defined 510 implementation using sprites 353 binary operators 496 532 BIN format See formats binning definition 510 bins 24 bins definition 510 blended transparency 337 bottlenecks 453 456 fill 455 host 453 transform 454 bounding volumes defined 511 See also volumes boxes axially aligned 408 broadcast video 13 buffer scope 221 defined 511 BYU format See formats Cc C 70 C See IRIS Performer C API C code examples xxviii caching intersections 460 state changes 450 callbacks culling 168 171 174 customized culling 158 discriminators for intersections 418 draw 171 174 function 171 node 171 post cull 172 post draw 172 pre cull 172 pre draw 172 process 174 CASEVision 467 casting 61 C c
168. 42 return gd A pfLightSource node s primary purpose is to represent a graphics library light source pfLight in a scene graph The position and orientation of the light source is affected by transformations inherited through the scene graph providing a simple means of moving lights about In conjunction with an object s material properties pfMaterial and the global lighting model pfLightModel illumination is computed at geometry vertices by the Geometry Pipeline While this kind of bread and butter lighting is very efficient it does not adequately simulate certain important lighting effects In particular per pixel spotlights and shadows are not supported by the default lighting mechanism On graphics library implementations which support texture mapping the pfLightSource node supports per pixel spotlights and opera lighting through a technique called projective texturing and also support shadows if shadow map hardware is available In practice default lighting is used in conjunction with projected texturing since the latter does not consider geometry normals but the former does Both projected texturing and shadows require a pfFrustum which defines the viewing volume of the light source The frustum s eye point is located at the pfLightSource position and the frustum s view direction is aligned along the pfLightSource s Y axis You can think of the frustum as a slide projector whose eyepoint is the proj
169. 460 494 Sproull Robert F xxix stack 486 stage definition 527 stages of rendering 214 stage timing graph 426 427 See also statistics Staples J K xxxii STAR format See formats state changes 450 defined 528 inheritance 156 local and global 358 state elements 333 state management 32 state specification global 358 local 358 static coordinate systems See pfSCS nodes static data in C classes 495 statistics 6 425 444 average 443 CPU 430 cumulative 443 current 443 data structures 425 443 displaying 425 426 434 enabling 436 fill 432 graphics 432 previous 443 stage timing defaults 435 graph 427 use in applications 434 stencil decaling 338 defined 528 stereo display 103 Stevens Brian L xxxii STL format See formats stress definition 528 stress management 31 210 stress management See load management structures libpfdu pfdBuilder 284 subclassing 490 subgraph definition 528 subpixels 24 subpixel Z buffer 24 SuperViewer 311 SV format See formats switch nodes 127 synchronization mode 63 synchronization of frames 195 system load management 31 557 Index T Tarbouriech Philippe xxix tearing 338 testing intersections See intersections visibility 162 Texas Instruments 300 texel definition 528 text 138 texture detail 465 environment mapping 25 magnification 465 minification 465 overview 25 26 sharpen 465 texture mapping d
170. 5 6 pfLayer Functions Function Description pfNewLayer Create a pfLayer node pfLayerMode Specify a hardware mode to use in drawing decals pfGetLayerMode Get current mode pfLayerBase Specify the child containing base geometry pfGetLayerBase Find out which child contains base geometry pfLayerDecal Specify the child containing decal geometry pfGetLayerDecal Find out which child contains decal geometry pfLayer nodes can be used to overlay any sort of markings on a given polygon and are important to avoid flimmering Example 5 6 demonstrates how to display runway markings as a decal above of a coplanar runway This example uses the performance mode PFDECAL_BASE_FAST for layering as described in the reference page other available modes are PFDECAL_BASE_HIGH_QUALITY PFDECAL_BASE_DISPLACE and PFDECAL_BASE_STENCIL 131 Chapter 5 Nodes and Node Types 132 Example 5 6 Marking a Runway With a pfLayer Node pfLayer layer pfGeode runway runway_markings avoid flimmering of runway and runway_markings layer pfNewLayer pfLayerBase layer runway pfLayerDecal layer runway_markings pfLayerMode layer PFDECAL_BASE_FAST pfLightPoint Nodes A pfLightPoint is a leaf node that represents a light point or set of light points Light points don t provide overall illumination for a scene rather they are discrete points that emanate light such as street lights and runway edge lights
171. 52 pfLayerMode 131 pfLengthQuat 405 pfLengthVec3 398 pfLightAmbient 137 pfLightAtten 349 pfLightColor 137 pfLightOff 137 pfLightOn Q 137 224 341 348 pfLightPos 137 pfLModelAtten 349 pfLoadMatrix 353 pfLoadMStack 407 pfLoadState 356 pfLoadTex 344 pfLoadTexFile 343 pfLODCenter 130 pfLODLODState 203 pfLODLODStateIndex 203 pfLODRange 130 pfLODTransition 207 pfLogQuat 405 pfLPointColor 132 236 pfLPointPos 133 237 pfLPointRot 132 237 pfLPointShape 133 237 pfLPointSize 132 236 pfLSourceAttr 242 244 pfLSourceColor 242 pfLSourceVal 243 pfMakeCoordMat 400 fMakeEulerMat 399 fMakeOrthoFrust 409 fMakePerspFrust 409 fMakePolarSeg 415 fMakePtsSeg 414 fMakeQuatMat 399 fMakeRotMat 399 fMakeRotOntoMat 399 fMakeRotQuat 405 fMakeScaleMat 400 fMakeTransMat 400 TOO U O O o O o SUV VVVUUVUUUUD OS ONO POO SO SO OS SO RO PO OS OO ES PSS fMalloc 47 227 325 386 386 387 388 461 fMergeBuffer 221 511 fModelMat 354 fMorphAttr 245 fMoveChan 102 105 fMovePWin 90 fMQueryFStats 438 442 fMQueryHit 180 181 417 fMQueryStats 438 442 fMtlColorMode 349 449 455 478 fMultipipe 217 218 fMultiprocess 75 214 215 217 218 220 427 452 475 481 493 fMultithread 217 218 fMultMat 401 fMultMatrix 224 353 fMultQuat 405 fNegateVec3 398 fNewBb
172. 6 pfObject 486 pfPlane 409 pfPolytope 485 pfQuat 404 485 pfSeg 414 485 pfSegSet 180 485 pfSphere 408 485 pfSprite 353 485 pfState 32 485 pfStats 425 443 486 533 Index pfString 330 485 pfTexEnv 485 pfTexGen 485 pfTexture 485 pflype 486 pfVec2 397 485 pfVec3 397 485 pfVec4 397 485 pfWindow 486 class hierarchy definition 512 class inheritance 42 definition 512 Clay Sharon xxix clearing the screen 32 clipped definition 512 clipping planes definition 512 clocks high resolution 384 cloned instancing 121 123 definition 512 cloning 31 cloning definition 513 close 391 closed loop control system 210 color tables 33 compiled mode 323 definition 513 compiler flags 69 compiling IRIS Performer applications 67 complex pixels definition 513 computer aided design xxv conferences I ITSEC xxxiii IMAGE xxxiv SIGGRAPH xxix SPIE xxxiv configuration pfChannel 92 534 pfFrustum 93 pfPipe 75 pfPipeWindow 79 pfScene 92 viewpoint 95 viewport 93 configuring IRIS Performer 62 configuring IRIS Performer See pfConfig containment frustum 162 conventions naming 35 typographical xxviii coordinate systems 95 dynamic See pfDCS nodes static See pf SCS nodes coplanar geometry 131 338 copying pfObjects 49 core dump from aggregate pfObject allocation 486 from mixing malloc and pfFree 386 from mixing pfMalloc and free 386 from static pfOb
173. 6 pfSelectWin 366 pfSelectWSConnection 374 pfSeqDuration 128 pfSeqInterval 128 pfSeqMode 128 pfSeqTime 128 pfSetMatCol 400 pfSetMatColVec3 400 pfSetMatRow 400 pfSetMatRowVec3 400 pfSetVec3 398 pfShadeModel 337 pfSharedArenaSize 386 388 pfSlerpQuat 405 pfSphereAroundBoxes 410 pfSphereAroundPts 410 pfSphereAroundSpheres 410 pfSphereContainsCyl 413 pfSphereContainsPt 412 pfSphereContainsSphere 413 pfSphereExtendByPt 410 pfSphereExtendBySphere 410 pfSpherelsectSeg 415 pfSpotLightCone 137 pfSpotLightDir 137 pfSpriteAxis 354 pfSpriteMode 354 pfSqrDistancePt3 398 pfSquadQuat 405 pfStageConfigFunc 76 pfStatsClass 433 438 pfStatsClassMode 437 438 439 pfStatsCountGSet 438 pfStatsHwAttr 433 438 pfStringColor 332 pfStringFont 330 pfStringMat 332 pfStringMode 332 pfSubloadTex 344 pfSubloadTexLevel 344 pfSubMat 401 pfSubVec3 398 pfSwitchVal 127 pfSync 63 65 157 193 428 452 pflevMode 449 pflexDetail 46 347 pflexFilter 346 449 pflexFormat 344 345 477 pflexFrame 345 pflexImage 46 343 344 pflexLevel 347 pflexList 345 pflexLoadImage 345 pflexLoadMode 343 345 346 pflexLoadOrigin 344 pflexLoadSize 344 pflexSpline 347 pffGenMode 347 pff GenPlane 348 pfIranslate 353 pfIransparency 224 333 336 358 449 456 pfIransposeMat 40
174. 7 intensity 237 light points 132 236 light sources 133 overview 348 light points 32 definition 520 Lightscape Technologies 287 499 Limber Michael xxix linear algebra 33 line segments 414 See also pfSegSet data structures linking IRIS Performer applications 67 link libraries 13 load definition 521 loaders 259 loading databases 37 loading files See databases load management 31 level of detail scaling 210 213 statistics 430 local state 358 locked phase definition 521 locks allocating 388 LOD level of detail managing 198 208 See also level of detail See also load management Loral Advanced Distributed Simulation 300 LSA See formats LSB See formats macros 466 PFADD_ SCALED _ VEC3 398 PFADD_VEC3 398 PFALMOST_EQUAL_MAT 402 PFALMOST_EQUAL_VEC3 399 PFCOMBINE_VEC3 398 PFCONJ_QUAT 405 PFCOPY_MAT 401 PFCOPY_VEC3 398 PFDISTANCE_PT3 398 PFDIV_QUAT 405 PFDOT_VEC3 398 PFEQUAL_MAT 402 PFEQUAL_VEC3 399 PFGET_MAT_COL 400 PFGET_MAT_COLVEC3 400 PFGET_MAT_ROW 400 PFGET_MAT_ROWVEC3 400 PFLENGTH_QUAT 405 PFLENGTH_VEC3 398 PFMAKE IDENT_MAT 399 PFMAKE SCALE MAT 400 PFMAKE_ TRANS_MAT 400 PFMATRIX 489 PFMULT_QUAT 405 PFNEGATE_VEC3 398 PFQUAT 489 PFSCALE_VEC3 398 PFSET_MAT_COL 400 PFSET_MAT_COLVEC3 400 PFSET_MAT_ROW 400 PFSET_MAT_ROWVEC3 400 PFSET_VEC3 398 PFSQR_DISTANCE_PT3 398 PFSUB_VEC3 398 PFVEC2 489 PFVEC3 489 PFVEC4 489 magic carpet 10 maili
175. 9 Example 10 10 Example 10 11 Example 10 12 Example 10 13 Example 11 1 Example 11 2 Example 11 3 Example 11 4 Example 11 5 Example 13 1 Setting Up a Partition 145 Inheritance demonstration program 146 Application Callback to Make a Pendulum 157 pfNode Draw Callbacks 173 Cull Process Callbacks 175 Using Passthrough Data to Communicate With Callback Routines 177 Frame Control Excerpt 198 Setting LOD Ranges 205 Default Stress Function 212 How to Configure a pfEarthSky 231 How to set up a pfLPointState 238 Projected texture and shadow pfLightSources 243 How to set up a pfMorph node 245 Loading Characters into a pfFont 330 Setting up and drawing a pfString 330 Using pfDecal to draw road with stripes 339 Pushing and Popping Graphics State 356 Using pfOverride 357 Inheriting State 359 Opening a pfWindow 364 Creating a Statistics Window 374 Using the Default Overlay Window 375 Creating a Custom Overlay Window 376 pfWindows and X Input 377 Constructing a Colored Cube With libpr 378 Constructing a Textured Cube With libpr 381 Matrix and Vector Math Examples 403 Quaternion Example 405 Quick Sphere Culling Against a Set of Half Spaces 414 Intersecting a Segment With a Convex Polyhedron 416 Intersection Routines in Action 419 Drawing an Object Without Calling pfDraw 465 Example 13 2 Example 13 3 Example 14 1 Example 14 2 Example 14 3 Example 14 4 Example 14 5 General Traversal 470 Using the Travers
176. AV_CONT needPop 0 pfNode prevNode trav gt node if node NULL pfNotify PFNFY_WARN PFNFY_USAGE MyTraverse Null node return PFTRAV_CONT for SCS and DCS push the transform on the stack 7 if pfIsOfType node pfGetSCSClassType amp amp trav gt mstack pfMatrix mat pfGetSCSMat pfSCS trav gt node mat pfPushMStack trav gt mstack pfPreMultMStack trav gt mstack mat needPop 1 call pre traversal callback trav gt node pfNode node if trav gt preFunc ret trav gt preFunc trav PFU_DO_RET ret after preFunc in case topology changed if pflsOfType node pfGetGroupClassType numChild pfGetNumChildren node if pflsOfType node pfGetGroupClassType for i 0 i lt numChild i trav gt depth ret MyTraverse pfNode pfGetChild group i trav trav gt depth 471 Chapter 13 Performance Tuning and Debugging 472 PFU_DO_RET ret PFU_DO_RET ret call post traversal callback trav gt node node if trav gt postFunc ret trav gt postFunc trav PFU_DO_RET ret if needPop pfPopMStack trav gt mstack return PEFTRAV_CONT BRK RK KK KK A A A AA A AA A AA A A A A A A A A A I Traversals and callbacks for installing and removing pre draw callbacks pfNodeTravFuncs for generating GL Prof tags during drawing WARNIN
177. BASE_HIGH_QUALITY or if there is no faster alternative on the current hardware platform which can cause performance degradations on some system pfFeature can be used to verify the availability and speed of these features on the current graphics platform The cost of specific fill operations can vary greatly depending on the graphics hardware configuration As a rule of thumb flat shading is much faster than Gouraud shading because it reduces both fill work and the host overhead of specifying per vertex colors Z buffering is typically next in cost and then stencil and blending On a RealityEngine the use of multisampling can add to the cost of some of these operations specifically z buffering and stenciling See Multisampling on page 476 for more information Texturing is considered free on RealityEngine and Impact systems but is relatively expensive on a VGX and is actually done in the host stage on lower end graphics platforms such as Extreme and XZ Some of the low end graphics platforms also implement z buffering on the host You may not be able to achieve benchmark level performance in all cases for all features For instance if you frequently change modes and you use short triangle strips you get much less than the peak triangle mesh performance quoted for the machine Fill rates are sensitive to both modes mode changes and polygon sizes As a general rule of thumb assume that fill rates average around 70 of peak on genera
178. COLORTABLE 342 PFSTATE_CULLFACE 335 PFSTATE_DECAL 335 PFSTATE_ENCOLORTABLE 336 PFSTATE_ENFOG 336 PFSTATE_ENHIGHLIGHTING 336 PFSTATE_ENLIGHTING 335 359 PFSTATE_ENLPOINTSTATE 336 PFSTATE_ENTEXGEN 336 PFSTATE_ENTEXTURE 336 359 PFSTATE_ENWIREFRAME 336 PFSTATE_FOG 342 PFSTATE_FRONTMTL 341 PFSTATE_HIGHLIGHT 342 PFSTATE_LIGHTMODEL 341 PFSTATE_LIGHTS 341 PFSTATE_LPOINTSTATE 342 PFSTATE_SHADEMODEL 335 PFSTATE_TEXENV 342 PFSTATE_TEXGEN 342 PFSTATE_TEXTURE 341 PFSTATE_TRANSPARENCY 333 335 PFSTATS_ENGFX 432 PFSTATS_ON 432 PFSTR_CENTER 332 PFSTR_CHAR 332 PFSTR_CHAR SIZE 332 PFSTR_FIRST 332 PFSTR_INT 332 PFSTR_JUSTIFY 332 PFSTR_LAST 332 PFSTR_LEFT 332 PFSTR_MIDDLE 332 PFSTR_RIGHT 332 PFSTR_SHORT 332 PFSWITCH_OFF 127 PFSWITCH_ON 127 PFTEX_BASE_APPLY 346 PFTEX_BASE_AUTO_REPLACE 345 PFTEX_BASE_ AUTO_SUBLOAD 346 PFTEX_FAST 346 PFTEX_FAST_DEFINE superceeded 345 PFTEX_LIST_APPLY 346 PFTEX_LIST_AUTO_IDLE 346 PFTEX_LIST_AUTO_SUBLOAD 346 PFTEX_LOAD BASE 343 346 PFTEX_LOAD LIST 346 PFTEX_SOURCE FRAMEBUFFER 344 PFTEX_SOURCE_ IMAGE 344 PFTEX_SOURCE_ VIDEO 344 PFTEX_SUBLOAD_FORMAT 344 PFTG_EYE_PLANE 348 PFTG_EYE_PLANE_IDENT 348 PFTG_OBJECT_PLANE 348 PFTG_SPHERE MAP 348 PFTR_BLEND_ALPHA 337 PFTR_FAST 336 PFTR_HIGH_QUALITY 336 PFTR_MS_ALPHA 337 PFTR_NO_OCCLUDE 337 PFTR_OFF 335 336 PFTR_ON 336 PFTRAV_CONT 171 184 418 PFTRAV_CULL 136 169 176 PFTRAV_DRA
179. CONT Continue and traverse the children of this node PFTRAV_PRUNE Skip the subgraph rooted at this node and continue PFTRAV_TERM Terminate the entire traversal 171 Chapter 6 Database Traversal 172 Callbacks are processed by the cull traversal in the following order 1 8 If a pre cull callback is defined then call the pre cull callback to get a cull result and find out whether traversal should continue Possible return values are listed in Table 6 2 If the pre cull callback returns PFTRAV_PRUNE the traversal returns to the parent and continues with the node s siblings if any If the callback returns PFTRAV_TERM the traversal terminates immediately Otherwise cull processing continues If the pre cull callback doesn t set the cull result using pfCullResult and view frustum culling is enabled then perform the standard node within frustum test and set the cull result accordingly If the cull result is PFIS_FALSE skip the traversal of children The post cull callback is invoked and traversal returns so that the parent node can traverse any siblings If a pre draw callback is defined then place a libpr display list packet in the display list so that the node s pre draw callback will be called by the draw process If running a combined CULLDRAW traversal invoke the pre draw callback directly instead Process the node continuing the cull traversal with each of the node s children or adding the node
180. Detail In creating LOD models and transitions for objects it s often safe to assume that the entire model should transition at the same time It s quite reasonable to make features of an automobile such as door handles disappear from the scene at the same time even when the passenger door is slightly closer than the driver s door It is much less clear that this approach would work for very large objects such as an aircraft carrier or a space station and it s clearly not acceptable for objects that span a large extent such as a terrain surface Attempts to handle large extent objects with discrete LOD tools focus on breaking the big object into myriad small objects and treating each small object independently This works in some cases but often fails at the junction between two or more independent objects where cracks or seams exist when different detail levels apply to the objects Some terrain processing systems have attempted to provide a hierarchy of crack filling geometry that is enabled based on the LOD selections of two neighboring terrain patches This digital grout becomes untenable when more than a few patches share a common vertex An alternate approach the active surface definition treats the entire terrain as a single connected and coherent surface The essence of the approach is that a triangle representing terrain either is judged to be 209 Chapter 7 Frame and Load Control Dynamic Load Management
181. ES PFDBLDR_AUTO_CMODE PFDBLDR_AUTO_DISABLE_TCOORDS_BY_STATE PFDBLDR_AUTO_DISABLE_NCOORDS_BY_STATE PFDBLDR_AUTO_LIGHTING_STATE_BY_NCOORDS PFDBLDR_AUTO_LIGHTING_STATE_BY_MATERIALS PFDBLDR_AUTO_TEXTURE_STATE_BY_TEXTURES PFDBLDR_AUTO_TEXTURE_STATE_BY_TCOORDS PFDBLDR_BREAKUP PFDBLDR_BREAKUP_SIZE PFDBLDR_BREAKUP_BRANCH PFDBLDR_BREAKUP_STRIP_LENGTH PFDBLDR_SHARE_MASK PFDBLDR_ATTACH_NODE_NAMES PFDBLDR_DESTROY_DATA_UPON_BUILD PFDBLDR_PF12_STATE_COMPATIBLE PFDBLDR_BUILD_LIMIT PFDBLDR_GEN_OPENGL_CLAMPED_TEXTURE_COORDS PFDBLDR_OPTIMIZE_COUNTS_NULL_ATTRS PFDBLDR_NODE_NAME_ COMPARE PFDBLDR_STATE_NAME_COMPARE Supported Database Formats Because the pfdBuilder is released as source code it is easy to add further functionality and more modes and attributes to even further customize this central functionality In fact because the pfdBuilder acts as a data funnel in converting data into IRIS Performer run time structures it is easy to control the behavior of many standard conversion tasks through merely globally setting builder modes which will subsequently affect all converters that use the pfdBuilder to process their data Supported Database Formats Vendors of several leading database construction and processing tools have provided database loading software for you to use with IRIS Performer This section describes these loaders the loaders developed by the IRIS Performer engineering team and several loaders developed in the IRIS
182. G removes any existing pre or post draw callbacks FA A A A A I I I I I HO He glprof pre draw traversal callback issues glprof_object calls PY static int cbGLProf pfTraverser trav void data const pfNode node pfGetTravNode trav const char nn static char name 80 if node NULL amp amp nn pfGetNodeName node if it exists use the node name for the tag strncpy name nn 79 else Performance Measurement Tools otherwise use the node type string for the tag strncpy name pfGetTypeName pfObject node 79 glprof_object name return 0 callback for placing glprof callbacks as pre draw callbacks on nodes ey static int cbhPutGLProfTag MyTraverser trav pfNode node trav gt node if node NULL amp amp pflsOfType node pfGetGeodeClassType pfNodeTravFuncs node PFTRAV_DRAW cbGLProf NULL return PFTRAV_CONT callback to remove the pre draw glprof tag callbacks ay static int cbRmGLProfTag MyTraverser trav pfNode node trav gt node if node NULL amp amp pflsOfType node pfGetGeodeClassType pfiIsofType node pfGetGroupClassType pfNodeTravFuncs node PFTRAV_DRAW NULL NULL return PFTRAV_CONT glprof object tag traversal void DoGLProfTraversal pfNode node int mode MyTraverser trav InitMyTraverser amp trav pfNotif
183. IRIS Performer Programmer s Guide Document Number 007 1680 030 CONTRIBUTORS Edited by Steven Hiatt Illustrated by Dany Galgani Production by Derrald Vogt Engineering contributions by Sharon Clay Brad Grantham Don Hatch Jim Helman Michael Jones Martin McDonald John Rohlf Allan Schaffer Chris Tanner and Jenny Zhao Copyright 1995 Silicon Graphics Inc All Rights Reserved This document contains proprietary and confidential information of Silicon Graphics Inc The contents of this document may not be disclosed to third parties copied or duplicated in any form in whole or in part without the prior written permission of Silicon Graphics Inc RESTRICTED RIGHTS LEGEND Use duplication or disclosure of the technical data contained in this document by the Government is subject to restrictions as set forth in subdivision c 1 ii of the Rights in Technical Data and Computer Software clause at DFARS 52 227 7013 and or in similar or successor clauses in the FAR or in the DOD or NASA FAR Supplement Unpublished rights reserved under the Copyright Laws of the United States Contractor manufacturer is Silicon Graphics Inc 2011 N Shoreline Blvd Mountain View CA 94039 7311 Indigo IRIS OpenGL Silicon Graphics and the Silicon Graphics logo are registered trademarks and Crimson Elan Graphics Geometry Pipeline ImageVision Library Indigo Elan Indigo Indy IRIS GL IRIS Graphics Library IRIS Indigo IR
184. IS InSight IRIS Inventor IRIS Performer IRIX Onyx Personal IRIS Power Series RealityEngine RealityEngine and Showcase are trademarks of Silicon Graphics Inc AutoCAD is a registered trademark of Autodesk Inc X Window System is a trademark of Massachusetts Institute of Technology IRIS Performer Programmer s Guide Document Number 007 1680 030 Contents Examples XV Figures xix Tables xxi About This Guide xxv Why Use IRIS Performer xxv What You Should Know Before Reading This Guide xxvi How to Use This Guide xxvi What This Guide Contains xxvii Conventions xxviii Bibliography xxix Computer Graphics xxix The IRIS GL and OpenGL Graphics Libraries xxx X Xt IRIS IM and Window Systems xxxi Visual Simulation xxxii Mathematics of Flight Simulation xxxii Virtual Reality xxxiii Geometric Reasoning xxxiii Conference Proceedings xxxiii Survey Articles in Magazines xxxiv Internet Resources xxxv Contents Getting Acquainted With IRIS Performer 3 Exploring the IRIS Performer Sample Scenes 3 Installing the Software 3 Exploring Code 9 Going Beyond Visual Simulation 10 Deciding Where to Start 10 IRIS Performer Basics 13 What Is IRIS Performer 13 Applications 16 Features 16 Survey of Visual Simulation Techniques 19 Low Latency Image Generation 21 Consistent Frame Rates 22 Rich Scene Content 23 Texture Mapping 25 Character Animation 26 Database Construction 28 Overview of th
185. IsectMask The mask in the pfGeoSet is useful when pfGeoSets are embedded in a larger data structure it allows you to define pfGeoSets to 417 Chapter 11 Math Routines 418 belong to different classes of geometry for intersection for example water ground foliage pfGSetIsectSegs also takes a mask and an intersection test is performed only if the bitwise AND of the two masks is nonzero Discriminator Callbacks If a callback is specified in pfGSetIsectSegs that function is invoked when a successful intersection occurs either with the bounding box of the pfGeoSet or with a primitive The discriminator can decide what action to take based on the information about the intersection contained in a pfHit object The return value from the discriminator determines whether the current intersection is valid and should be copied into the return structure whether the rest of the geometry in the pfGeoSet is examined and whether the segment should be clipped before continuing Unless the return value includes the bit PFTRAV_IS_IGNORE the intersection is considered successful and is copied into the array of pfHit structures for return The bits of the PFTRAV_ tokens determine whether to continue as shown in Table 11 12 Table 11 12 Discriminator Return Values Result Meaning PFTRAV_CONT Continue examining geometry inside the pfGeoSet PFTRAV_PRUNE Terminate the traversal now PFTRAV_TERM Terminate the traversal now
186. LAY_WIN will also automatically create and open a statistics window if one has not already been set and if the current window cannot support statistics This mode only has effect for X windows AUTO_RESIZE The graphics window and active alternate configuration windows are automatically resized to match the parent pfWinWSWindow This mode is enabled by default and only has effect for X windows ORIGIN_LL The origin of the pfWindow for placement purposes will be the lower left corner X uses the upper left corner as the origin and pure IRIS GL uses the lower level This mode is enabled by default EXIT The application will receive a DeleteWindow message upon selection of the Exit from the window system menu on the window border This mode only has effect for X windows 373 Chapter 10 libpr Basics 374 Communicating with the Window System You can communicate with a local or remote window server by means of a window system connection a pfWSConnection in X also known as a Display connection You can use your pfWSConnection for selecting X events for your window as is demonstrated in Example 10 11 Libpr offers several utilities for creating a connection to a window server A given connection can communicate with any screen managed by that window server so usually a process only needs one connection A process should not share the connection of another process so you will need a connection per process Typically t
187. LITY ifdef USE_TEXTURE_MAPPING_FOR_DIRECTIONALITY Use texture mapping for directionality CPU computes size and range and fog attenuation P pfLPStateMode lps PFLPS_DIR_MODE PFLPS_DIR_MODE_TEX pfLPStateMode lps PFLPS_TRANSP_MODE PFLPS_TRANSP_MODE_ALPHA pfLPStateMode lps PFLPS_FOG_MODE PFLPS_FOG_MODE_ALPHA pfuMakeLPStateShapeTex lps tex 256 pfGStateAttr gst PFSTATE_TEXTURE tex pfTGenMode tgen PF_S PFTG_SPHERE_MAP pfTGenMode tgen PF_T PFTG_SPHERE_MAP else Use texture mapping for range and fog attenuation CPU computes size and directionality pfLPStateMode lps PFLPS_DIR_MODE PFLPS_DIR_MODE_ALPHA pfLPStateMode lps PFLPS_TRANSP_MODE PFLPS_TRANSP_MODE_TEX pfLPStateMode lps PFLPS_FOG_MODE PFLPS_FOG_MODE_TEX pfuMakeLPStateRangeTex lps tex 256 pfNewFog NULL pfGStateAttr gst PFSTATE_TEXTURE tex pfTGenPlane tgen PF_S 0 0f 0 0f 1 0f 0 0f pfTGenPlane tgen PF_T 0 0f 0 0f 1 0f 0 0f pfTGenMode tgen PF_S PFTG_EYE_PLANE_IDENT pfTGenMode tgen PF_T PFTG_EYE_PLANE_IDENT endif pfGStateAttr gst PFSTATE_TEXGEN tgen pfGStateMode gst PFSTATE_ENTEXGEN 1 Make PFGS_POINTS pfGeoSet arranged in a sphere gd pfNewGecde gs pfNewGSet
188. LOD node is a list of ranges that define the distance at which each model is appropriate to display There is no limit to the number of levels of detail that can be used Figure 7 2 Level of Detail Node Structure The object can be transformed as needed During the culling phase of frame processing the distance from the eyepoint to the object is computed and used with other factors to select which LOD model to display The IRIS Performer pfLOD node contains a value known as the center of LOD processing The LOD center point is an x y z location that defines the point used in conjunction with the eyepoint for LOD range switching calculations as described in the Level of Detail Range Processing section of this chapter Figure 7 3 shows an example in which multiple LOD models grouped under a parent LOD node are used to represent a toy racecar Level of Detail Management Blend zones Switch ranges Figure 7 3 Level of Detail Processing Figure 7 3 demonstrates that each car in a row of identical cars placed at increasing range from the eyepoint is drawn using a different child of the tree s LOD node 201 Chapter 7 Frame and Load Control 202 The double ended arrows indicate a switch range for each level of detail When the car is closer to the eyepoint than the first range nothing is drawn When the car is between the first and second ranges LOD 1 is drawn When the car is between the second a
189. LSA files is consistently counter clockwise and polygon normals are not specified The first few lines of the LSA sample file chamber 0 lsa provide an example of the format 0 486911 0 03228900 0 979046 0 9596590 1 665110 0 00944197 0 286293 0 2806240 0 000000 1 92730000 0 017805 0 0174524 0 240398 5 54670000 13 021200 13 4945000 1782 4751 0 0 t 4 35 7 3677 2 57 6188666 6 5 9 3 2 57 5663353 4 35 9 3 2 57 5728890 t 6 5 9 3 2 57 5663353 4 35 7 3677 2 57 6188666 6 5 8 2463 2 57 6057596 The count line indicates that the file contains 1782 independent triangles and 4751 independent quadrilaterals which together represent 11 284 triangles The image in Figure 9 7 shows this database the New Jerusalem City Hall This was produced by A J Diamond of Donald Schmitt and Company Toronto Canada using the Lightscape Visualization system Description of Supported Formats Figure 9 7 LSA Format City Hall Database pfdLoadFile uses the function pfdLoadFile_lsa to load LSA format files into IRIS Performer run time data structures Files in the LSB binary format have a very different structure from LSA files Representing not just polygon data they contain much of the structural information present in the s files used by the Lightscape Visualization system including material layer and texture definitions as well as a hierarchical mesh definition for geometry This information is structured as a series of data secti
190. MIT APP_CULL_DRAW Draw 13 3ms tris 1701 verts 2540 Figure 12 1 Stage Timing Statistics Display The statistics diagram in Figure 12 1 is the simplest of the standard statistics displays There are several other standard display formats each emphasizing other classes of statistics Statistics collection though highly optimized can take extra time in IRIS Performer operations Because of this you have a great deal of fine control over exactly what statistics are currently being collected and what statistics are being displayed Statistics are divided into classes separated into vertically stacked boxes in a display and into modes within each class The next several sections describe the classes shown in a typical statistics display Interpreting Statistics Displays Status Line The top line of a standard statistics display above the box that the rest of the statistics are drawn in shows the current average frame rate followed by a slash and the target frame rate To set a target frame rate call pfFrameRate The rest of that status line indicates what frame rate control method you re using FLOAT FREE LIMIT or LOCK for details see Achieving the Frame Rate in Chapter 7 your multiprocess model set with pfMultiprocess and the average time in milliseconds spent in the channel draw callback An optional part of the status line indicates the number of triangles in the scene Stage Timing Graph The main p
191. MakeRotQuat q2 angle2 axis 0 pfMakeQuatMat m3q q2 7 axis 1y axis 1 axis 1 axis 1 AssertEqMat m2 m3q make rot quat q2 angle 1 0f t anglel t angle2 pfMakeRotMat m3 angle axis 0 pfMakeRotQuat ql anglel axis 0 pfMakeRotQuat q2 angle2 axis 0 pfSlerpQuat q3 t ql q2 pfMakeQuatMat m3q q3 AssertEqMat m3q m3 quaternion axis 2 axis 2 axis 2 axis 2 axis 1 axis 2 axis 1 axis 1 slerp axis 2 axis 2 Matrix Stack Operations Matrix Stack Operations IRIS Performer allows you to create a stack of transformation matrices which is called a pfMatStack Table 11 4 lists and describes the matrix stack routines Note that none of these routines has a macro equivalent The matrix at the top of the matrix stack is denoted TOS for Top of Stack Table 11 4 Matrix Stack Routines Routine pfNewMStack pfResetMStack pfPushMStack pfPopMStack pfPreMultMStack pfPostMultMStack pfLoadMStack pfGetMStack pfGetMStackTop pfGetMStackDepth pfPreTransMStack pfPostTransMStack pfPreRotMStack pfPostRotMStack pfPreScaleMStack pfPostScaleMStack Operation Allocate storage Reset the stack Duplicate the TOS and push it on the stack Pop the stack Premultiply the TOS by a matrix Postmultiply the TOS by a matrix Set the TOS matrix Get the TOS matrix Get a pointer to the TOS matrix Retur
192. Mode mtl side PEMTL_CMODE_AD e Uses a large number of specialized routines for rendering different kinds of objects extremely quickly There s a specialized drawing routine for each possible pfGeoSet configuration each choice of primitive type attribute bindings and index selection Each time you 449 Chapter 13 Performance Tuning and Debugging 450 change from one pfGeoSet to another one of these specialized routines is called However this happens even if the new pfGeoSet has the same configuration as the old one so larger pfGeoSets are more efficient than smaller ones the function call overhead for drawing many small pfGeoSets can reduce performance As a rule of thumb a pfGeoSet should contain at least 4 triangles and preferably between 8 and 64 If the pfGeoSet is too large it can reduce the efficiency of other parts of the process pipeline Caches state changes because applying state changes is costly in the draw stage IRIS Performer accumulates state changes until you call one of the pfApply functions at which point it applies all the changes at once Note that this differs from the graphics libraries in which state changes are immediate If you have several state changes to make in IRIS Performer set up all the changes before applying them rather than using the one change at a time approach with each change followed by an apply operation that you might expect if you re used to graphics library progr
193. MtlColor mtl PFMTL_DIFFUSE GetDfRed GetDfGreen GetDfBlue pfMtlColor mtl PE SPECULAR GetSpRed GetSpGreen GetSpBlue pfMtlShininess mtl GetMtlShininess j pfMtlAlpha mtl GetMtlAlpha pfdBldrStateAttr PFSTATE_FRONTMTL mtl pfdBldrStateAttr PFSTATE_BACKMTL mtl break case GRAPHICS STATE STORE pfdSaveBldrState GetStateName 265 Chapter 9 Importing Databases 266 break case GRAPHICS_STATE LOAD pfdLoadBldrState break case GRAPHICS_STATE pfdPushBldrState GetStateName PUSH break case GRAPHICS_STATE_POP pfdPopBldrState break case GRAPHICS _STATE_ RESET pfdResetBldrState break case GRAPHICS_STATE __CAPTURE_DEFAULT BldrState pfdCaptureDefault break case BEGIN_LEAF_NOD Not really nec destroyed on b pfdResetBldrGeome break case END_LEAF_NOD 7 pfNode nd if nd NU pfAddChild break One of the fundamental structures essary because it is uild try pfdBuild LL root nd involved in the above routine outline is the pfdGeom structure which users fill in with information about a single primitive or a single strip of primitives The pfdGeom structure is essential in communicating with the pfdBuilder and is defined as follows typedef struct _pfdGeom int flags int nbind c bind
194. Multiprocessing With IRIS Performer m Advanced This section describes an advanced topic that applies only to systems with more than one CPU If you don t have a multiple CPU system you may want to skip this section IRIS Performer uses multiprocessing to increase throughput for both rendering and intersection detection Multiprocessing can also be used for tasks that run asynchronously from the main application like database management Although IRIS Performer hides much of the complexity involved you need to know something about how multiprocessing works in order to use multiple processors well 213 Chapter 7 Frame and Load Control 214 Review of Rendering Stages Recall from Chapter 3 that an IRIS Performer application renders images using one or more pfPipes as independent software rendering pipelines The flow through the rendering pipeline can be modeled using these functional stages Intersection Test for intersections between segments and geometry to simulate collision detection or line of sight for example Application Do requisite processing for the visual simulation application including reading input from control devices simulating the vehicle dynamics of moving models updating the visual database and interacting with other networked simulation stations Cull Traverse the visual database and determine which portions of it are potentially visible perform level of detail selection for models with multiple r
195. NN t Nr OW e A Sae ome os N N Ae Ww ome POLYS Description of Supported Formats S29 LO de 2 lt 4 13 14 15 16 lt 5 17 18 19 20 lt 6 21 22 23 24 lt pfdLoadFile uses the functions pfdLoadFile_poly and pfdLoadFile_bpoly to import data from poly and bpoly format files into IRIS Performer run time data structures Brigham Young University BYU Format The Brigham Young University byu format is used as an interchange format by some finite element analysis packages The IRIS Performer loader for byu files is located in the usr share Performer src libfibpfdb libpfbyu directory The format of a BYU file consists of four parts as defined below 1 A text line containing four counts the number of parts the number of vertices the number of polygons and the number of elements in the connectivity array 2 The part definition list containing the starting polygon number and ending polygon number one pair per line for parts lines 3 The vertex list which has the X Y Z coordinates of each vertex in the database packed two per line This means that vertices 1 and 2 are on the first line 3 and 4 are on the second and so on for vertices 1 2 lines of text in the file 4 The connectivity array with an entry for each polygon These entries may span multiple lines in the input file and each consists of three or more vertex indices with the last negated as an end of
196. OORD3 PFGS_PER_VERTEX r E7 memdup BBVertCoords sizeof BBVertCoords arena NULL pfGSetAttr gset PFGS_TEXCOORD2 PFGS_PER_VERTEX memdup BBTexCoords sizeof BBTexCoords arena NULL pfGSetAttr gset PFGS_COLOR4 PFGS_OVERALL memdup BBColors sizeof BBColors arena NULL pfGSetPrimLengths gset int memdup BBPrimLens sizeof BBPrimLens pfGSetPrimType gset PFGS_QUADS pfGSetNumPrims gset 1 pfGSetGState gset gst bill pfNewBboard switch bbType case PF_X axial rotate case PF_Y case PF_Z pfBboardAxis bill BBAxes bbType pfBboardMode bill PFBB_ROT PFBB_AXIAL_ROT break case 3 point rotate pfBboardAxis bill BBAxes bbType arena r pfBboardMode bill PFBB_ROT PFBB_POINT_ROT_WORLD break pfAddGSet bill gset pfBboardPos bill 0 pos 143 Chapter 5 Nodes and Node Types 144 return bill pfPartition Nodes A pfPartition is a pfGroup that organizes the scene graphs of its children into a static data structure that can be more efficient for intersections Currently partitions are only useful for data that lies more or less on an XY plane such as terrain A pfPartition would therefore be inappropriate for a skyscraper model Partition construction comes in two phases After a piece of the scene graph has been placed under the pfPartition pfBuildPart examines
197. PFFB_RED_SIZE 8 PFFB_SAMPLES 8 PFFB_ STENCIL SIZE 1 NULL main pfPipe pipe pfPipeWindow pwin pfiInit pfConfig Create pfPipeWindow for pfPipe 0 pipe pfGetPipe 0 pwin pfNewPWin pipe Set the framebuffer configuration pfPWinFBConfigAttrs Shared gt pw FBAttrs Indicate that the window is ready to open pfOpenPWin pwin trigger the opening of the window in the draw 89 Chapter 4 Setting Up the Display Environment 90 pfFrame If you want to do all of your own window creation and management you can do so and just give IRIS Performer the handles to your windows with the pfPWinWSDrawable function you may also provide a parent X window with the pfPWinWSWindow function pfOpenPWin will make use of any windows that have already been provided More details regarding the creation and configuration of pfPipeWindows and pfWindows are discussed in Chapter 10 libpr Basics pfPipeWindows in Action pfPipeWindows allow for a reasonable amount of flexibility in the running application Management of channels in pfPipeWindows is discussed later in this chapter in the Section Using Multiple Channels pfPipeWindows can be re ordered on their parent pfPipe to control the order that they are drawn in with the command pfMovePWin pipe index pwin pfPipeWindows can be dynamically opened and closed in th
198. PI called for instance a user might define a brick state with a red material and a brick texture Later he might just want to say brick is the current state and then input the walls of several buildings This type of state naming is accomplished by fully specifying the state to be named via the immediate mode API and then calling pfdSaveBldrState This state can then be recalled via pfdLoadBldrState ParselIIMFile FILE iimFile pfGroup root pfdGeom poly while op GetNextOp iimFile NULL switch op Developing Custom Importers case G EOMETRY_POLYGON polygon gt numVerts GetNumVerts iimFile Determine if polygon has Texture Coords if pfdGetBldrStateMode PFSTATE_ENTEXTURE PF_ON polygon gt tbind PFGS_PER_VERTEX else polygon gt tbind PFGS_OFF Determine if Polygon has normals if AreThereNormalsPerVertex TRUE polygon gt nbind PFGS_PER_VERTEX else if pfdGetBldrStateMode PFSTATE_ENLIGHTING PF_ON polygon gt nbind PFGS_PER_PRIM else polygon gt nbind T PFGS_OFF Determine if Polygon has colors if AreThereColorsPerVertex TRUE polygon gt cbind PFGS_PER_VERTEX else if AreThereColorsPerPrim TRUE polygon gt cbind PFGS_PER_PRIM else polygon gt cbind PFGS_OFF for i 0 i lt polygon gt numVerts i R
199. Performer header files include lt Performer pf h gt include lt Performer pfutil h gt include lt Performer pfdu h gt Overview Declare variables for the required elements pfScene a scene graph to be rendered on a channel pfPipe a graphics pipeline to perform the rendering pfChannel a view to be rendered on the designated pipe You can configure IRIS Performer to use multiple scenes multiple pipes if your system has them and multiple channels per pipe See Using Multiple Channels in Chapter 4 Initialize IRIS Performer pfiInit This sets up the shared memory arena used for multiprocessing initializes the high resolution clock and resets IRIS Performer s state Configure IRIS Performer pfconfig This configures the number of pipes and starts processes based on the selected multiprocessing model The code in Example 3 1 uses the defaults a single pipe and a multiprocessing model that is tailored to the number of processors on the machine Load or create the database root pfdLoadFile argv 1 pfdLoadFile loads a database from the disk using whichever file importer seems appropriate based on the three letter extension at the end of the given filename There are other ways to set up scenes too for instance you can call a specific importing routine in place of pfdLoadFile if you want to load only databases of a particular format or you can create geometric objects directly using libpr a
200. Performer user community for other database formats Importing your databases is simple if they re in formats for which IRIS Performer database loaders have already been written Each of the loaders listed in Table 9 6 is included with IRIS Performer If you want to import or export databases in any of these formats refer to the appropriate section of this chapter for specific details about the individual loaders Table 9 6 Supported Database Formats Name Description 3ds AutoDesk 3DStudio binary data bin SGI format used by powerflip bpoly Side Effects Software PRISMS binary data byu Brigham Young University CAD FEA data dwb Coryphaeus Software Designer s Workbench data dxf AutoDesk AutoCAD ASCII format flt11 MultiGen public domain Flight v11 format flt14 MultiGen OpenFlight v14 format 269 Chapter 9 Importing Databases 270 Table 9 6 continued Supported Database Formats Name Description gds McDonnell Douglas GDS things data gfo Old SGI radiosity data format im Simple IRIS Performer data format irtp AAI Graphicon Interactive Real Time PHIGS iv SGI Open Inventor format VRML 1 0 superset Isa Lightscape Technologies ASCII radiosity data Isb Lightscape Technologies binary radiosity data medit Medit Productions medit modeling data nff Eric Haines ray tracing test data obj Wavefront Technologies data format pegg Radiosity research data format phd SGI polyhedron data format poly Side Effects S
201. RAW 215 216 450 452 PFMP_CULLoDRAW 215 216 427 PFMP_FORK_CULL 215 PFMP_FORK_ DBASE 220 PFMP_FORK_DRAW 214 215 216 PFMP_FORK_ISECT 217 PFMPASS_NONTEX_SCENE 243 PFMTL_CMODE_AD 455 PFNFY_ALWAYS 392 PFNFY_DEBUG 254 392 475 559 Index PFNFY_FATAL 386 392 PFNFY_FP_DEBUG 392 393 PFNFY_INFO 392 PFNFY_NOTICE 392 PFNFY_WARN 392 PFPB_LEVEL 368 PFPHASE_FLOAT 195 PFPHASE_FREE RUN 195 PFPHASE_LIMIT 195 PFPHASE_LOCK 195 PFPK_M_ALL 185 PFPK_M_NEAREST 185 PFPROC_APP 76 PFPROC_CULL 76 PFPROC_DBASE 76 PFPROC_DRAW 76 PFPROC_ISECT 76 PFPWIN_TYPE_NOPORT 366 PFPWIN_TYPE_OVERLAY 366 PFPWIN_TYPE_SHARE 81 PFPWIN_TYPE_STATS 81 365 PFPWIN_TYPE_X 81 365 PFOFTR_LIGHT_ATTENUATION 349 PFOFTR_LMODEL_ATTENUATION 349 PFQOHIT_FLAGS 180 181 PFQHIT_GSET 181 PFOHIT_NAME 181 PFOHIT_NODE 181 PFOHIT_NORM 181 PFQHIT_PATH 181 PFOHIT_POINT 180 PFQOHIT_PRIM 181 PFOHIT_SEG 180 PFOHIT_SEGNUM 180 PFQHIT_TRI 181 PFOHIT_VERTS 181 PFOHIT_XFORM 181 PFSM_FLAT 337 PFSM_GOURAUD 335 337 PFSORT_BACK_TO_FRONT 168 PFSORT_BY_STATE 167 560 PFSORT_END 167 PFSORT_FRONT_TO_BACK 167 PFSORT_NO_ORDER 167 PFSORT_QUICK 168 PFSORT_STATE_BGN 167 PFSORT_STATE_END 167 PFSPRITE_AXIAL_ROT 354 PFSPRITE_MATRIX_THRESHOLD 354 PFSPRITE_POINT_ROT_EYE 354 PFSPRITE_POINT_ROT_WORLD 354 PFSPRITE_ROT 354 PFSTATE_ALPHAFUNC 335 PFSTATE_ALPHAREF 340 PFSTATE_ANTIALIAS 335 PFSTATE_BACKMTL 341 PFSTATE_
202. SMat 127 pfGetFilePath 393 pfGetFileStatus 391 pfGetGSet 138 139 pfGetLayerBase 131 pfGetLayerDecal 131 pfGetLayerMode 131 pfGetLightAmbient 137 pfGetLightColor 137 pfGetLightPos 137 pfGetLODCenter 130 pfGetLODRange 130 pfGetLPointColor 132 pfGetLPointPos 133 pfGetLPointRot 132 pfGetLPointShape 133 pfGetLPointSize 132 pfGetMatCol 400 pfGetMatColVec3 400 pfGetMatRow 400 pfGetMatRowVec3 400 pfGetMStack 407 pfGetMStackDepth 407 pfGetMStackTop 407 pfGetNumChildren 117 pfGetNumGSets 138 139 pfGetOrthoMatCoord 400 pfGetOrthoMatQuat 400 pfGetParent 168 pfGetParentCullResult 173 pfGetPartAttr 145 pfGetPartType 145 pfGetPipe 76 pfGetPipeScreen 76 pfGetPipeSize 77 pfGetPWinCurOriginSize 88 pfGetPWinCurScreenOriginSize 88 pfGetQuatRot 405 pfGetRef 47 pfGetSCSMat 126 pfGetSemaArena 227 386 388 pfgetSemaArena 356 pfGetSeqDuration 128 pfGetSeqFrame 128 pfGetSeqInterval 128 pfGetSeqMode 128 pfGetSeqTime 128 pfGetSharedArena 226 325 386 pfGetSize 387 pfGetSpotLightCone 137 pfGetSpotLightDir 137 pfGetSwitchVal 127 pfGetTime 34 384 pfGetType 50 pfGetTypeName 51 pfGetVClock 385 pfGetWinCurOriginSize 367 pfGetWinCurScreenOriginSize 367 pfGetWinFBConfig 371 pfGetWinFBConfigData 370 pfGetWinGLCxt 371 pfGetWinOrigin 366 pfGetWinSize 366
203. SpotLightDir leftHeadlight 0 0f 1 0f 0 0f pfSpotLightCone leftHeadlight 1 0f 30 0f pfSpotLightDir rightHeadlight 0 0f 1 0f 0 0f pfSpotLightCone rightHeadlight 1 0f 30 0f Turn on headlights This isn t really necessary since pfLightSources are on by default LightOn leftHeadlight LightOn rightHeadlight Fy Fh Create car geometry and add to car DCS pfAddChild car initCarGeometry Attach headlights to moving car pfAddChild car leftHeadlight pfAddChild car rightHeadlight In Example 5 9 both the position and spotlight direction of the light sources are transformed by the combination of the car s pf DCS and all other pfDCS or pfSCS nodes above it in the scene graph Note that we specified to pfLightPos that the pfLightSource have a location with the fourth coordinate nonzero This defines a local light source an infinite light source has zero for its fourth coordinate An infinite light source has only a direction not a location it emits parallel rays because it is considered 135 Chapter 5 Nodes and Node Types 136 infinitely far away The sun for example is approximated as an infinite light source Transformations change only the direction of an infinite light source not its position Also note in Example 5 9 that a pfSwitch isn t necessary to turn a pfLightSource on or off you can directly switch a pfLightSource with pfLightOn and pfL
204. Sys PFQSYS_MAX_STENCIL_BITS amp sten bits PF_MIN2 4 sten pfStatsHwAttr PFSTATSHW_FILL_DCBITS bits Initialize GL win pfNewWin NULL pfWinOriginSize win 100 100 500 500 pfWinName win Iris Performer pfWinType win PFWIN_TYPE_X PFWIN_TYPE_STATS pfOpenWin win Example 10 9 demonstrates the creation of a window with a default overlay window Example 10 9 Using the Default Overlay Window int main void pfWindow win over Initialize Performer pfInit pfInitState NULL Initialize the window win pfNewWin NULL pfWinOriginSize win 100 100 500 500 pfWinName win Iris Performer pfWinType win PFWIN_TYPE_X pfWinMode win PFWIN_HAS_OVERLAY 1 pfOpenWin win First select and draw into the overlay window pfWinIndex win PFWIN_OVERLAY_WIN Select causes the index to be applied pfSelectWin win Then select the main gfx window pfWinIndex win PFWIN_GFX_WIN pfSelectWin win 375 Chapter 10 libpr Basics 376 Example 10 10 demonstrates creating a custom overlay window and is taken from the sample program usr share Performer src pguide libpr C winfbconfig c Example 10 10 Creating a Custom Overlay Window static int OverlayAttrs PFFB_LEVEL 1 Level 1 indicates overlay visual PFFB _BUFFER_SIZE 8 None int main void
205. TENCIL 369 PFFB_STEREO 368 PFFB_USE_GL 369 PFFOG_PIX_EXP 350 PFFOG_PIX_EXP2 350 PFFOG_PIX_LIN 350 PFFOG_PIX_SPLINE 350 351 PFFOG_VTX_EXP 350 PFFOG_VTX_EXP2 350 PFFOG_VTX_LIN 350 PFFONT_BBOX 329 PFFONT_CHAR_ SPACING 329 PFFONT_CHAR_SPACING_FIXED 329 PFFONT_CHAR_SPACING_VARIABLE 329 PFFONT_GSTATE 329 PFFONT_NAME 329 PFFONT_NUM_CHARS 329 PFFONT_RETURN_CHAR 329 PFFONT_SPACING 329 PFGS_COLOR4 349 PFGS_COMPILE_GL 323 328 PFGS_FLAT_LINESTRIPS 321 327 PFGS_FLAT_TRISTRIPS 322 327 PFGS_FLATSHADE 322 PFGS_LINES 321 PFGS_LINESTRIPS 321 PFGS_OFF 327 PFGS_OVERALL 327 PFGS_PER_PRIM 327 PFGS_PER_VERTEX 327 PFGS_POINTS 237 321 PFGS_POLYS 322 PFGS_QUADS 322 417 PFGS_TRIS 321 417 PFGS_TRISTRIPS 322 417 PFGS_WIREFRAME 322 PFHL_BBOX_FILL 352 PFHL_BBOX_LINES 352 PFHL_FILL 352 PFHL_FILL_R 352 PFHL_FILLPAT 352 PFHL_FILLPAT2 352 PFHL_FILLTEX 352 PFHL_LINES 351 PFHL_LINES_R 352 PFHL_LINESPAT 351 PFHL_LINESPAT2 351 PFHL_NORMALS 352 PFHL_POINTS 352 PFHL_SKIP_BASE 352 PFIS_ALL_IN 172 173 413 415 PFIS_FALSE 172 412 413 416 PFIS_MAYBE 413 415 PFIS_PICK MASK 185 PFIS_START_IN 415 PFIS_TRUE 412 413 415 416 PFLS_INTENSITY 244 PFLS_PROJ_FOG 244 PFLS_PROJ_FRUSTUM 242 PFLS_PROJ_TEX 242 PFLS_SHADOW_SIZE 243 PFMP_APP_CULL_DRAW 215 217 224 226 428 PFMP_APP_CULLDRAW 215 216 224 PFMP_APPCULL_DRAW 215 217 PFMP_APPCULLDRAW 215 216 217 475 PFMP_CULL_DL_D
206. Table 11 9 Testing Volume Intersections Routine Action Test if A Inside B pfHalfSpaceContainsSphere Sphere inside a half space pfFrustContainsSphere Sphere inside a frustum pfSphereContainsSphere Sphere inside a sphere pfSphereContainsCyl Cylinder inside a sphere pfHalfSpaceContainsCyl Cylinder inside a half space pfFrustContainsCyl Cylinder inside a frustum pfHalfSpaceContainsBox Box inside a half space pfFrustContainsBox Box inside a frustum pfBoxContainsBox Box inside a box The volume volume intersection tests are designed to quickly locate empty intersections for rejection during a cull If the complete intersection test is too time consuming the result PFIS_MAYBE is returned to indicate that the two volumes might intersect The returned value is a bitwise OR of tokens as shown in Table 11 10 Table 11 10 Intersection Results Test Result Meaning PFIS_FALSE No intersection PFIS_MAYBE Possible intersection PFIS_MAYBE PFIS_TRUE PFIS_MAYBE PFIS_TRUE PFIS_ALL_IN A contains at least part of B A contains all of B 413 Chapter 11 Math Routines This arrangement allows simple code such as that shown in Example 11 3 Example 11 3 Quick Sphere Culling Against a Set of Half Spaces long HSSContainsSphere pfPlane hs pfSphere sph long numHS long i isect isect 0 for i 0 i lt numHS itt isect amp pfHalfSpaceContainsSphere sph hs i if isect PFIS_FALSE return
207. W 176 PFTRAV_IS_BCYL 186 PFTRAV_IS_CACHE 452 PFTRAV_IS_CLIP_END 184 418 PFTRAV_IS_CLIP_START 184 418 PFTRAV_IS_CULL_BACK 186 PFTRAV_IS_GEODE 184 PFTRAV_IS_GSET 184 186 417 PFTRAV_IS_IGNORE 184 418 PFTRAV_IS_NO_PART 144 PFTRAV_IS_NODE 186 PFTRAV_IS_PRIM 184 417 PFTRAV_MULTIPASS 243 PFTRAV_PRUNE 171 172 184 418 PFTRAV_TERM 171 172 184 418 PFWIN_AUTO_RESIZE 373 PFWIN_EXIT 373 PFWIN_GFX_WIN 83 372 PFWIN_HAS_OVERLAY 373 PFWIN_HAS_ STATS 373 PFWIN_NOBORDER 373 PFWIN_ORIGIN_LL 373 PFWIN_OVERLAY_WIN 83 372 373 PFWIN_STATS_WIN 83 372 PFWIN_TYPE_NOPORT 365 366 PFWIN_TYPE_OVERLAY 365 PFWIN_TYPE_STATS 366 total animation 28 total latency 21 tour through simple c 55 transformations affine 402 definied 529 inheritance through scene graph 156 order of composition 402 orthogonal 402 orthonormal 402 411 specified by matrices 399 transition distance definition 529 transparency 24 336 476 477 transparency in textures 25 transport delay 21 561 Index traversals 31 activation 154 application 157 attributes 154 culling 153 158 166 customizing 158 166 node pruning 159 visibility testing 159 163 database See databases definition 529 draw 153 169 intersection 153 179 187 overview 31 triangle meshing 36 TRI format See formats trigger routine definition 529 Truxal Carol xxxiv Tucker Johanathan B xxxiv twinkle 24 type actual o
208. Window 3pf reference page For sample programs involving windows and input handling see usr share Performer src pguidef libpr libpf libpfutil libpfui X and IRIS IM The X Window System is a network based hardware independent window system for use with bitmapped graphics displays In the X client server model an X server running in the background handles input and output and informs client applications when various events occur A special client the window manager places windows on the screen handles icons and manages the titles and borders of windows IRIS IM is Silicon Graphics port of OSF Motif a set of widgets for use with Xt the X toolkit intrinsics library With the pfWindow window functions that IRIS Performer provides you don t need to know X or IRIS IM to use windows However if you want to learn about those topics anyway see the books mentioned in the Bibliography on page xxix 41 Chapter 2 IRIS Performer Basics pfObjects and the Class Hierarchy 42 IRIS Performer provides an object oriented programming interface to most of its data structures Only IRIS Performer functions can change the values of elements of these data structures for instance you must call pfMtlColor to set the color of a pfMaterial structure rather than modifying the structure directly Instances of these encapsulated data types are referred to as pfObjects In addition some simple data types are not encapsulated
209. _VTX_EXP2 Compute fog exponentially at vertices e squared PFFOG_PIX_LIN Compute fog linearly at pixels PFFOG_PIX_EXP Compute fog exponentially at pixels e PFFOG_PIX_EXP2 Compute fog exponentially at pixels e squared PFFOG_PIX_SPLINE Compute fog using a spline function at pixels pfFogType uses these tokens to set the type of fog A detailed explanation of fog types is given in the reference page for pfFog 3pf and the IRIS GL fogvertex 3g and OpenGL glFog 3g reference pages Graphics State You can set the near and far edges of the fog with pfFogRange For exponential fog functions the near edge of fog is always zero in eye coordinates The near edge is where the onset of fog blending occurs and the far edge is where all pixels are 100 fog color The token PFFOG_PIX_SPLINE selects a spline function to be applied when generating the hardware fog tables This is further described in the pfFog 3pf reference page Spline fog allows the user to define an arbitrary fog ramp that can more closely simulate real world phenomena like horizon haze For best fogging effects the ratio of the far to the near clipping planes should be minimized In general it s more effective to add a small amount to the near plane than to reduce the far plane Highlights IRIS Performer provides a mechanism for highlighting geometry with alternative rendering styles useful for debugging and interactivity A pfHighlight created with
210. a 1 PFIS_FALSE PFIS_TRUE Figure 6 1 Culling to the Frustum Chapter 6 Database Traversal 162 Visibility Testing The cull traversal begins at the root node of a channel s scene graph the pfScene node and continues downward directed by the results of the cull test at each node At each node the cull test determines the relationship of the node s bounding volume to the viewing frustum Possible results are that the bounding volume is entirely outside is entirely within is partially within or completely contains the viewing frustum If the intersection test indicates that the bounding volume is entirely outside the frustum the traversal prunes that node that is it doesn t consider the children of that node and continues with the node s next sibling If the intersection test indicates that the bounding volume is entirely inside the frustum the node s children are not cull tested because the hierarchical nature of bounding volumes implies that the children must also be entirely within the frustum If the intersection test indicates that the bounding volume is partially within the frustum or that the bounding volume completely contains the frustum the testing process continues with the children of that node Because a bounding volume is larger than the object it surrounds it is possible for a bounding volume to be partially within a frustum even when none of its enclosed geometry is visible
211. a pfStats and a pfPipeWindow has a pfWindow In these cases the first object in each pair provides functions corresponding to those of the second For example pfFrustum has a routine pfMakeSimpleFrust frust 45 0f and pfChannel has a corresponding routine pfMakeSimpleChan channel 45 0f All of the major classes in IRIS Performer are derived from the pfObject class It unifies the data types by providing common attributes and functions However some distinctions remain between libpr objects and libpf objects due to memory and performance considerations User Data The primary attribute of a pfObject is called user data its primary functions are pfDelete pfCopy and pfPrint Each pfObject contains a special pointer to void which is reserved for application use This pointer can be set with pfUserData to point to a user supplied data structure This user structure usually further describes the pfObject by adding attributes that make sense to the application Both libpf and libpr objects have user data pointers 45 Chapter 2 IRIS Performer Basics 46 pfDelete and Reference Counting Most kinds of data objects in IRIS Performer can be placed in a hierarchical scene graph using instancing see Instancing in Chapter 5 when an object is referenced multiple times Scene graphs can become quite complex which can cause problems if you re not careful Deleting objects can be a particularly dangerou
212. able Commands added to a reset display list overwrite any previously entered commands A display list is typically reset at the beginning of a frame and then filled with the visible scene pfDispLists support concurrent multiprocessing where the producer and consumer processes simultaneously write and read the display list The PFDL_RING argument to pfNewDList creates a ring buffer or FIFO type display list pfDispLists automatically ensure ring buffer consistency by providing synchronization and mutual exclusion to processes on ring buffer full or empty conditions State Management pfState is a structure that represents the entire libpr graphics state A pfState maintains a stack of graphics states that can be pushed and popped to save and restore state The top of the stack describes the current graphics state of a window as it s known to IRIS Performer pfInitState initializes internal libpr state structures and should be called at the beginning of an application before any pfStates are created Multiprocessing applications should pass a usinit semaphore arena 355 Chapter 10 libpr Basics 356 pointer to pfInitState such as pfGetSemaArena so IRIS Performer can safely manage state between processes pfNewState creates and returns a handle to a new pfState which is typically used to define the state of a single window If using pfWindows discussed in Windows on page 363 a pfState is automatically created
213. ace to the graphics libraries This interface eliminates the guesswork of the tuning process by providing optimized data structures and performance tuned renderers The interface is intuitive easy to learn and flexible enough to let you plug any application into the hooks provided by libpr to access the full set of graphics library features libpr is platform independent so you can realize performance gains across the entire Silicon Graphics product line Note Both libpr and libpf object files are incorporated into a single library called libpf so the routines can be arranged in memory to improve caching behavior However libpr is still conceptually a stand alone library and is referred to a such in the following discussion Design Motivation A great deal of specialized knowledge is required to tune the performance of any piece of software A primary design goal of IRIS Performer is to provide you with that knowledge in the form of an easy to use toolkit The design decisions implemented in libpr combine an understanding of subtle machine level implications with hands on experience in tuning a variety of applications 317 Chapter 10 libpr Basics 318 Applications that you develop using IRIS Performer will approach peak performance on both current and future hardware and software releases so you don t have to spend a lot of time porting and tuning your code every time you make an upgrade to your system Key Features li
214. ack 2 v3 2 cpack 3 v3 3 polygon cpack 4 v3f 4 cpack 5 v3 5 coack 6 v3 6 cpack 7 v3 7 polygon cpack 7330 v3 7330 coack 7331 v3 7331 cpack 7332 v3f 7332 cpack 7333 v3 7333 instance polygon 0 polygon 1 pol Lygon 2675 This example is taken from the file barcelona l gfo one of only two known databases in the GFO format The importer uses functions from the libpfdu library such as those from the pfdBuilder to generate efficient shared triangle strips This increases the speed with which GFO databases can be drawn and reduces the size and complexity of the loader since the builder s functions hide the details of the pfGeoSet construction process Silicon Graphics IM Format The im format is a simple format developed for test purposes by the IRIS Performer engineering team As new features are added to IRIS Performer the im loader is extended to allow experimentation and testing A recent example of this is support for pfText pfString and pfFont objects which can be seen by running perfly on the sample data file fontsample im The IRIS Performer im loader is in the usr share Performer src lib libpfdb libpfim directory Here is an example IM format file that creates an extruded 3D text string Copy this to a file ending in the extension im and load it into Perfly For a complete example of how text is handled in IRIS Performer use Perfly to
215. acter and a new line The optional information includes color specification in the form c R G B A a normal vector of the form n NX NY NZ or a texture coordinate in the form uv S T where the values in parentheses are floating point numbers Here is asample POLY format file for a cube with colors texture coordinates and normals specified at each vertex POINTS 0 5 0 5 0 5 c 0 0 0 1 uv 0 0 n 0O 1 0 OS 0 50 5 E 07 0 1p aL avi 0 0 na Oy 17 0 0 25 00 10 59 S Le Op Ty 1 cue 0 n 0 7 c lt 0 0 5 0400 045 1 20 20 0 Dk wwiCl 0 a Oy Ly 0 05 0 5 0 5 eO 07 Tp aw 0520 60 0 1 SOrD 04 5405 e300 1 dy Ly av Oy Ly O 0 1 0 50 5 OS cls Ly ape 2 veh 1 mG07 07 1 02 S 20 5055 ECT Oy l E suas On 077 Oy aL 059 045 05 56 00 1 ye ae av Oy ul m4 ag 20 0 5 0 5 0 5 c 0 1 0 1 uv 0 1 n 0O 1 0 055 e 1 1 09 1 ruv It 2h CO Ty 0 ty ly 1 curds Don 05 2 0 OMAANA UO BWN FE DIK TARWON POW ww ee O ol oO ol fo uo 0 O O 1 uv 0O 0 n 0 0 1 hy Oy OY a oasa A O a a EO 0 843 pp dy OO Lay A Oo Qy EL Of Ty 07 1 av 0 4 wO 07 1 0 O O 1 uv 0O 0 n 1 0 O 0 1 0 1 uv 0 1 n 1 0 O Tya dey Ly ar 0 2 a S 20 0 Dy hy Ty av Os 0 ney Oy 2 r Ly LY awl ao arity 0 Ip dp 05 T aa Lg t aay 0 1 0 0 1 uv 1 0 n 1 0 0 1 O de 2 uw Ly 0 ard 0 0 N
216. agated down the process pipeline and then back up to the application process to be included in the PREV buffer In a libpf application most statistics collection is completely automatic The application must simply enable the desired classes of statistics via pfStatsClass and or pfStatsClassMode The IRIS Performer processes are responsible for actually opening the pfFrameStats structure in which to accumulate the enabled statistics classes as well as for managing any statistics hardware resources All types of libpf statistics can be accumulated without ever making specific calls to open a structure for accumulation or enabling statistics hardware When using only libpr statistics however one must explicitly open a pfStats structure for statistics accumulation by calling pfOpenStats Hardware statistics resources must also be managed by an application using only libpr statistics Statistics function calls that have HW in their names such as pfEnableStatsHw and pfStatsHwAttr directly access system Collecting and Accessing Statistics in Your Application hardware such as graphics hardware and CPU be careful to make such calls only from the relevant process pfEnableStatsHw expects PFSTATSHW_EN bitmask tokens Statistics classes which have corresponding statistics hardware have a PFSTATSHW_ prefix in their token names Ina libpf application IRIS Performer takes care of enabling the correct hardware modes that c
217. ail is appropriate for a given distance to the eyepoint The sections that follow describe how to create multiple LOD models and how to control when the changeover to a different LOD occurs Level of Detail Models Most objects comprise smaller objects that become visually insignificant at ranges where the conglomerate object itself is still quite prominent For example a complex model of an automobile might have door handles side and rear view mirrors license plates and other small details A short distance away these features may no longer be visible even though the car itself is still a visually significant element of the scene It is important to realize that as a group these small features may contain as many polygons as the larger car itself and thus have a detrimental effect on rendering speed You can construct two LOD models simply by providing one model that contains all of the detailed features and another model that contains only the car body itself and none of the detailed features A more sophisticated scheme uses multiple LOD models that are grouped under an LOD node 199 Chapter 7 Frame and Load Control 200 Figure 7 2 shows an LOD node with multiple children numbered 1 through n In this case the model named LOD 1 is the most detailed model and models LOD 2 through LOD n represent progressively coarser models Each of these LOD models might contain children that also have LOD components Associated with the
218. ails on geometric objects without making those details into actual geometry One valuable and widely used addition to these texture processing features is the concept of partly transparent textures An example of this is the use of billboards see pfBillboard Nodes in Chapter 5 For instance to display a tree using textures and billboards create a texture map of a tree from a photograph perhaps marking the background any part of the texture which does not show part of the tree as transparent Then using a flat rectangle for the billboard map the texture to the billboard the transparent regions in the texture become transparent regions of the billboard allowing other geometry to show through Environment Mapping You can use textures to simulate reflections usually in a curved surface of a 3D environment such as a room by using the viewing vector and the geometry s surface normal to compute each screen pixel s index into the texture image The texture used for this process the environment map must contain images of the environment to be reflected Sophisticated Shading You can use the environment mapping technique to implement lighting equations by noting that the environment map image represents the image seen in each direction from a chosen point Interpreting this image as the illumination reflected from an incident light source as a function of angle the intensities rather than the colors of the environment map can b
219. aintain control of your simulation loop The Motif interface is created in its own process and Motif event handlers and callbacks will be executed in that process The Motif callbacks set flags in shared memory to communicate with the main application Part of this communication is the sharing of X windows between IRIS Performer and Motif The example program usr share Performer src pguide libpf C motif c demonstrates the basic elements of this integrated IRIS Performer Motif hook up 91 Chapter 4 Setting Up the Display Environment Using Channels 92 This section describes how to use pfChannels A pfChannel is a view of a graphics scene A pfChannel is a required element for an IRIS Performer application because it establishes the visual frame of reference for what is rendered in the drawing process Creating and Configuring a pfChannel When you create a new pfChannel it is attached to a pfPipe for the duration of the application The pfPipe renders the pfScene viewed by the pfChannel into a pfPipeWindow that is managed by that pipe The simplest method uses one channel one window and one pipe You can use multiple channels in a single pfWindow on a pfPipe thereby allowing channels to share hardware resources Using multiple channels is an advanced topic that is discussed in the section of this chapter on Using Multiple Channels For now focus your attention on understanding the concepts of setting up and using a single c
220. alled a display list during a compilation stage This data structure is highly optimized for efficient transfer to the graphics hardware However compiled mode has some major disadvantages e compilation is usually costly e adisplay list must be recompiled whenever its pfGeoSet s attributes change e the display list uses extra memory In general immediate mode will offer excellent performance with minimal memory usage and no restrictions on attribute volatility which is a key aspect in may advanced applications Despite this experimentation may show cases where compiled mode offers a performance benefit To enable or disable compiled mode call pfGSetDrawMode with the PFGS_COMPILE_GL token When enabled compilation is delayed until the next time the pfGeoSet is drawn with pfDrawGSet Subsequent calls to pfDrawGSet will then send the compiled pfGeoSet to the graphics hardware Primitive Connectivity A pfGeoSet requires a coordinate array that specifies the world coordinate positions of primitive vertices This array is either indexed or not depending on whether a coordinate index list is supplied If the index list is supplied it s used to index the coordinate array if not the coordinate array is interpreted in a sequential order A pfGeoSet s primitive type dictates the connectivity from vertex to vertex to define geometry Figure 10 1 shows a coordinate array consisting of four coordinates A B C and D and the g
221. also exist to aid in the design of roadways instrument panels and terrain surfaces The reward of building complex databases that accurately and efficiently represent the desired virtual environment is great however since real time image generation systems are only as good as the environments they re used to explore Overview of the IRIS Performer Libraries Overview of the IRIS Performer Libraries This section outlines the basic elements of each library The ibpf Visual Simulation Library libpf is the visual simulation development library Functions from libpf make calls to libpr functions libpf thus provides a high performance yet easy to use interface to the hardware Multiprocessing Framework libpf provides a pipelined multiprocessing model for implementing visual simulation applications The pipeline stages are e application e cull e draw The application stage updates and queries the scene The cull stage traverses the scene and adds all potentially visible geometry to a special libpr display list which is then rendered by the draw stage Rendering pipelines can be split into separate processes from one to three to tailor the application to the number of available CPUs In addition IRIS Performer provides an intersection stage which may be multiprocessed that intersects line segments with the database for things like collision detection and line of sight determination Multiprocess operation is largely
222. am pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis if pfCylContainsPt amp cyl pt printf 0 9 halfLength not in cylinder n pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis if pfCylContainsPt amp cyl pt printf 0 9 halfLength not in cylinder n pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis pfAddScaledVec3 pt pt 0 9f cyl radius perp if pfCylContainsPt amp cyl pt printf printf 0 9 halfLength not in cylinder n pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis pfAddScaledVec3 pt pt 0 9f cyl radius perp if pfCylContainsPt amp cyl pt printf 0 9 halfLength not in cylinder n pfAddScaledVec3 pt cyl center 1 1f cyl halfLength cyl axis if pfCylContainsPt amp cyl pt printf 1 1 halfLength in cylinder n pfAddScaledVec3 pt cyl center 1 1f cyl halfLength cyl axis if pfCylContainsPt amp cyl pt printf 1 1 halfLength in cylinder n pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis pfAddScaledVec3 pt pt 1 1f cyl radius perp if pfCylContainsPt amp cyl pt printf 1 1 radius in cylinder n pfAddScaledVec3 pt cyl center 0 9f cyl halfLength cyl axis pfAddScaledVec3 pt pt 1 1f cyl radius perp if pfCylContainsPt amp cyl pt printf 1 1 radius in cylinder n
223. ame The operation name always precedes the type name In this case the operation name is unabbreviated and the type name is abbreviated For example the name of the routine that applies a pflexture is pfApplyTex Compound type names are abbreviated by the first initial of the first word and the entire second word For example to draw a display list which is type pfDispList use pfDrawD List Symbolic token names incorporate another abbreviation usually shorter of the type name For example pfTexture tokens begin with PFTEX_ pfDispList tokens begin with PFDL_ This convention ensures that tokens for a particular type have their own name space Other tokens and identifiers follow the conventions of ANSI C and C wherein a valid identifier consists of upper and lower case alphabetic characters digits and underscores and the first character must not be a digit Further details of these coding conventions as they pertain to C programming are described in Chapter 14 Programming with C 35 Chapter 2 IRIS Performer Basics 36 The libpfdu Geometry Builder Library libpfdu is a database utilities library It provides helpful functions for constructing optimized IRIS Performer data structures and scene graphs It s used mainly by database loaders which take an external file format containing 3D geometry and graphics state and load them into IRIS Performer optimized run time only structur
224. amming Evaluates state changes lazily that is it avoids making any redundant changes When you apply a state change IRIS Performer compares the new graphics state to the previous one to see if they re different If they are it checks whether the new state sets any modes If it does IRIS Performer checks each mode being set to see whether it s different from the previous setting To take advantage of this feature share pfGeoStates and inherit states from the global state wherever possible Set all the settings you can at the global level and let other nodes inherit those settings rather than setting each node s attributes redundantly To do this within a database you can set up pfGeoStates with your desired global state and apply them to the pfChannel or pfScene with pfChanGState or pfSceneGState You can do this through the database loader utilities in libpfdu trivially for a given scene with pfdMakeSharedScene or have more control over the process with pfdDefaultGState pfdMakeSceneGState and pfdOptimizeG StateList Provides an optimized immediate mode rendering display list data type pfDispList in libpr The pfDispList type reduces host overhead in the drawing process and requires much less memory than a graphics library display list libpf uses pfDispLists to pass results from the cull process to the draw process when the PFMP_CULL_DL_DRAW mode is turned on as part of the multiprocessing model For more How IRIS
225. and static coordinate systems Fixed frame rate capability Shadows and spotlights Morphing Visual simulation features An environmental model Light points 17 Chapter 2 IRIS Performer Basics Animation sequences Sophisticated fog and haze control Landing light capabilities Billboarded geometry Geometry Builder Library ibpfdu Features e Allows input in immediate mode fashion simplifying database conversion e Produces optimized IRIS Performer data structures Tessellates input polygons including concave and recombines triangles into high performance meshes Automatically shares state structures between geometry when possible Produces scene graph containing optimized pfGeoSets and pfGeoStates Utility Library ibpfutil Features e Processor isolation routines e GLX mixed mode utilities e Device input and event handling both IRIS GL and X versions e Cursor control e Simple and efficient GUI and widgets e Scene graph traversal utilities e Texture animation or movies e Smoke and fire effect simulation User Interface Library ibpfui Features e Trackball fly and drive motion models e Collision models 18 Survey of Visual Simulation Techniques Survey of Visual Simulation Techniques Computers have generated interactive simulated virtual environments usually for training or entertainment since the 1960s Computer image generation CIG has not always been a r
226. and the portion of the geometry beyond the clipping plane is mathematically trimmed and discarded clipping planes The normal clipping planes are those that define the viewing frustum These are the left right top bottom near and far clipping planes All rendered geometry is clipped to the intersection of the half spaces defined by these planes and only the portion inside all six is displayed by the graphics hardware cloned instancing The style of instancing that creates a possibly partial copy of a node hierarchy rather than simply making a reference to the parent node This allows pfDCS nodes and other internal nodes to be changed in the copy without changing those in the original Also see shared instancing cloning Making a copy of a data structure recursively copying down to some specified level In IRIS Performer pfCopy creates a shallow copy pfClone creates a deeper copy that creates new copies of internal nodes but not of leaf nodes This means that the pfDCS pfSwitch and other internal nodes in the cloned hierarchy are separate from those in the original compiled mode IRIS Performer pfGeoSets are designed for rapid immediate mode rendering and in most situations outperform IRIS GL and OpenGL display list usage In those cases where GL display lists are desired pfGeoSets may be placed in compiled mode whereby a GL display list will be created the first time the pfGeoSet is rendered and this display list wil
227. and triangles within each strip it therefore makes sense to have several triangles in each strip and several strips in each set If you put only two triangles in a pfGeoSet you ll spend all that loop overhead on drawing those two triangles when you could be drawing many more with little extra cost The channel statistics can display as part of the graphics statistics a histogram showing the percentage of your database that is drawn in triangle strips of certain lengths 453 Chapter 13 Performance Tuning and Debugging Only bind vertex attributes that are actually in use For example if you bind per vertex colors on a set of flat shaded quads the software will waste work by sending those colors to the graphics pipeline which will ignore them Similarly it s pointless to bind normals on an unlit pfGeoSet Nonindexed drawing has less host overhead than indexed drawing because indexed drawing requires an extra memory reference to get the vertex data to the graphics pipeline This is most significant for primitives that are easily host limited such as independent polygons or very short triangle strips However indexed drawing can be very helpful in reducing the memory requirements of a very large database Enable state sorting for pfChannels this is the default By sorting the CPU does not need to examine as many pfGeoStates The graphics channel statistics can be used to report the pfGeoSet to pfGeoState drawing ratio Trans
228. annel call pfFStatsClass pfGetChanFStats chan PFSTATS_ALL PFSTATS_OFF Use the same function with different parameters to enable all or specific classes of statistics for a channel You can specify which classes to enable in order to minimize statistics collection overhead Statistics in ibprand libpf pfStats Versus pfFrameStats libpf statistics accumulate into a pfFrameStats structure to later be displayed printed queried or otherwise operated on The pfFrameStats structure actually contains four buffers of statistics a buffer for the previous frame s statistics a buffer of averaged statistics for the previous update period a buffer of accumulated statistics for the current update period and a buffer of statistics being accumulated for the current frame The pfFrameStats structure is built upon the libpr pfStats structure so the pfFrameStats API includes routines to duplicate the functionality of pfStats The duplicated API exists because the routines cannot be intermixed pfStats routines can only be used on pfStats structures and pfFrameStats routines can only be called with pfFrameStats structures However pfstats classes and class modes designated with the PFSTATS_ prefix can be enabled ona pfFrameStats structure The pfStats statistics classes include the system and hardware statistics for the graphics pipeline and the CPU as well the pixel fill statistics and rendering statistics on geometry graphics state a
229. ant in the profiling output When running a program for profiling run a set number of frames and then use the automatic exit described below Using gldebug and og ldebug to Observe Graphics Calls You can use the graphics utilities gldebug IRIS GL and ogldebug OpenGL to both debug and tune IRIS Performer applications The application must be run in single process mode in order to use gldebug but ogldebug can handling multiprocessed programs Use gldebug or ogldebug to e Show which graphics calls are being issued e Look for frequent mode changes or unnecessary mode settings that can be caused if your initialization of the global state doesn t match the majority of the database e Look for unnecessary vertex bindings such as unneeded per vertex colors or normals for a flat shaded object Follow these steps to examine one frame of the application in a gldebug session 1 Start up profiler of choice IRIS gldebug i ignore s F your_prog_name prog_options OPEN ogldebug your_prog_name prog_options 2 Turn off output and breakpoints from the control panel 3 Seta breakpoint at swapbuffers or glXSwapBuffers Performance Measurement Tools 4 Click the Continue button and go to the frame of interest 5 Turn on breakpoints Execution stops at swapbuffers or glXSwapBuffers 6 Turn on all trace output 7 Click the Continue button Execution stops at the next swapbuffers outputting one full scene
230. aphics contexts can be created for the window using pfWindows pfPipeWindows and pfWindows allow you to have a list of alternate pfWindows that render to exactly the same screen area but may have different framebuffer configuration You can then select the current configuration for a pfPipeWindow with pfPWinIndex There are two kinds of common alternate configuration windows that can be created automatically for you overlay windows created in the overlay planes and windows to support hardware fill statistics discussed in Chapter 12 Statistics You can use pfPWinMode to indicate that you would like these windows created for you automatically Special tokens to pfPWinIndex are used to select these common special alternate configuration windows PFWIN_GFX_WIN PFWIN_OVERLAY_WIN and PFWIN_STATS WIN where PFWIN_GFX_WIN selects the normal default drawing window Note that only a pfWindow never a pfPipeWindow can be an alternate configuration window Further details on creating and using alternate configuration windows are discussed with pfWindows in Chapter 10 libpr Basics The source code in Example 4 3 is taken from usr share Performer src pguide libpf C pipewin c and demonstrates the automatic creation and selection of overlay and statistics windows for a pfPipeWindow This also shows usage of pfChannels and interaction 83 Chapter 4 Setting Up the Display Environment 84 between pfPipeWindows and pfChannels that will
231. ar argv float t 0 0f pfScene scene pfNode root pfPipe p pfPipeWindow pw pfChannel chan pfSphere bsphere if argc lt 2 pfNotify PFNFY_FATAL PFNFY_USAGE Usage simple file ext n exit 1 Initialize Performer pfiInit Select multiprocessing mode based on number of processors z pfMultiprocess PFMP_DEFAULT Load all loader DSO s before pfConfig forks pfdInitConverter argv 1 Initiate multi processing mode set by pfMultiprocess FORKs for Performer processes CULL and DRAW etc happen here pfConfig Overview Append to Performer search path PFPATH files in usr share Performer data ane pfFilePath usr share Performer data Read a single file of any known type if root pfdLoadFile argv 1 NULL pfExit exit 1 Attach loaded file to a new pfScene scene pfNewScene pfAddChild scene root Create a pfLightSource and attach it to scene pfAddChild scene pfNewLSource Configure and open graphics window p pfGetPipe 0 pw pfNewPWin p pfPWinType pw PFPWIN_TYPE_X pfPWinName pw IRIS Performer pfPWinOriginSize pw 0 0 500 500 Open and configure the GL window pfOpenPWin pw Create and configure a pfChannel chan pfNewChan p pfChanScene chan scene pfChanFOV chan 45 0f
232. arena pfGSetPrimType gs PFGS_POINTS pfGSetNumPrims gs NPOINTS 240 Light Points colors pfMalloc sizeof pfVec3 NPOINTS arena coords pfMalloc sizeof pfVec3 NPOINTS arena norms pfMalloc sizeof pfVec3 NPOINTS arena pfGSetAttr gs PFGS_NORMAL3 PFGS_PER_VERTEX norms NULL pfGSetAttr gs PFGS_COLOR4 PFGS_PER_VERTEX colors NULL pfGSetAttr gs PFGS_COORD3 PFGS_PER_VERTEX coords NULL ion lt lt pfGSetGState gs gst pfAddGSet gd gs Squash sphere into an ellipse so perspective point size is more easily seen pfMakeRotMat squash 90 0f 1 0f 0 0f 0 0f pfPostScaleMat squash squash 1 0f 2 0f 5f pfiInvertAffMat squashInvTransp squash pfTransposeMat squashInvTransp squashInvTransp dphi 180 0f NPOINTS2 1 dtheta 360 0f NPOINTS2 phi dphi for k 0 i 0 i lt NPOINTS2 2 i float Ct st Spy cps theta 0 0f pfSinCos phi amp sp amp cp for j 0 J3 lt NPOINTS2 j k pfSetVec4 colors k 1 0f 1 0f 1 0f 1 0f pfSinCos theta amp st amp ct pfSetVec3 norms k ct sp st sp cp pfScaleVec3 coords k 10 0f norms k pfXformPt3 coords k coords k squash pfXformVec3 norms k norms k squashInvTransp pfNormalizeVec3 norms k theta dtheta phi dphi 241 Chapter 8 Creating Visual Effects Spotlights and Shadows 2
233. art of the timing display is the stage timing graph occupying the top portion of the statistics display The red vertical lines the darker ones in Figure 12 1 mark video retrace intervals which occur at the video refresh rate of the system commonly 60 times per second a field is the period of time between two video retrace boundaries The green vertical lines the lighter ones in the figure indicate frame boundaries Note that frame boundaries are always on field boundaries and are an integral number of fields The segmented horizontal line segments in the top portion of the timing graph show the time taken by each of the IRIS Performer pipeline stages i intersection a application c cull and d draw for each of the four frames shown 0 through 3 On screen all stages belonging to a given frame are drawn in one color different colors indicate different frames The stages of the most recent frame at the right of the graph are marked a0 c0 and d0 previous frames have higher numbers so a 1 indicates the application stage of the immediately previous frame All stages performed by the same IRIX process are connected by vertical lines If two stages are performed by different processes they are not connected by a vertical line In most multiprocessing modes a stage of one frame occurs at the same time as another stage for a different frame so that for instance d0 is directly below c 1 in the graph The exception is the
234. assure safe multiprocess operation with any DSOs providing C virtual functions or defining new pfTypes Initialization should be carried out in the following sequence 1 Call pfInit This initializes the type system and for libpf applications sets up shared memory 2 Initialize any application supplied classes a Load any application specific C DSOs b Call pfdInitConverter to initialize and load any converter DSOs c Enter any user supplied pfTypes into the type system e g call Rotor init 3 Call pfConfig This forks off other processes as specified by pfMultiprocess 4 Create libpf and libpr objects 493 Chapter 14 Programming with C Note Pure libpr applications that do their own multiprocessing outside of IRIS Performer with fork should explicitly create shared memory with pfInitArenas before calling pfInit Otherwise the type system will not be visible in the address space of other processes More on Shared Memory and the Type System IRIS Performer objects or other objects that use pfTypes can only be shared between related processes Related processes are those created with fork or sproc from the main process after pfInit in a libpf application e g processes created by pfConfig New pfTypes should be added before pfConfig forks off other processes so that the static data member containing the class type is visible in all processes otherwise pf lt Class gt getClassType wil
235. at is expensive and should be avoided when possible Quaternion Operations Because a pfQuat is also a pfVec4 all of the pfVec4 routines and macros may be used on pfQuats as well Table 11 3 Routines for Quaternions Routine Effect Macro Equivalent pfMakeRotQuat q a x y z Sets q to rotation of a none degrees about x y z pfGetQuatRot q a x y z Sets a to angle and none x y z to axis of rotation represented by q pfConjQuat d q d conjugate of q PFCONJ_QUAT pfLengthQuat q returns length of q PFLENGTH_QUAT pfMultQuat d q1 q2 d q1 q2 PFMULT_QUAT pfDivQuat d q1 d2 d ql ql PFDIV_QUAT pfInvertQuat d q1 d 1 ql pfExpQuat d q d exp q none pfLogQuat d q d In q none pfSlerpQuat d t q1 q2 d interpolationwith none weight t between q1 t 0 0 and q2 t 1 0 pfSquadQuat d t q1 q2 a b d quadratic none interpolation between q1 and q2 pfQuatMeanTangent d q1 q2 d mean tangent of none q3 q1 q2 and q3 Example 11 2 Quaternion Example test quaternion slerp M7 pfQuat ql q2 q3 pfMatrix ml m2 m3 m3q 405 Chapter 11 Math Routines 406 pfVec3 axis float anglel angle2 angle t MakeRandomVec3 axis pfNormalizeVec3 axis anglel drand48 90 0f angle2 drand48 90 0f t drand48 pfMakeRotMat m1 anglel axis 0 pfMakeRotQuat ql anglel axis 0 pfMakeQuatMat m3q ql pfMakeRotMat m2 angle2 axis 0 pf
236. ate a pfState for IRIS Performer s state management Windows For X windows IRIS Performer maintains two windows and a graphics context The top level X window is the one that placed on the screen and is the one that you should use in your application for selecting X events This top level window is very lightweight and has minimal resources allocated to it IRIS Performer then maintains a separate X window that is a child of the parent X window and is the one that is attached to the graphics context This allows you to select different framebuffer resources for the same drawing area by just selecting a different graphics window and graphics context pair for the parent X window pfWindows directly support this functionality and this is discussed in the next section Manipulating a pfWindow Finally with OpenGL you may choose to draw to a different X Drawable than a window X windows are created with the X function XCreateWindow Mixed model IRIS GL windows have an X window serve as both the graphics drawable and the GL context OpenGL graphics contexts are created with glXCreateContext The parent X Window can be set with pfWinWSWindow the graphics window or X Drawable is set with pfWinWSDrawable and the OpenGL graphics context is set with pfWinGLCxt For compatibility between GLs IRIS Performer defines the following GL and Window System independent types defined in Table 10 21 If you create your own window but want to use
237. ate about an axis as is done for a tree or a lamp post or constrained only by a point as when simulating a cloud or a puff of smoke Specify the rotation mode by calling pfBboardMode specify the rotational axis by calling pfBboardAxis Since rotating the geometry to the eyepoint doesn t fully constrain the orientation of a point rotating billboard modes are available to use the additional degree of freedom to align the billboard in eye space or world space Usually the normals of billboards are specified to be parallel to the rotational axis to avoid lighting anomalies pfFlatten is highly recommended for billboards If a billboard lies beneath a pfSCS or pfDCS an additional transformation is done for each billboard This can have a substantial performance impact on the cull process where billboards are transformed Table 5 11 describes the functions for working with pfBillboards Table 5 11 pfBillboard Functions Function Description pfNewBboard Create a pfBillboard node pfBboardPos Set a billboard s position pfGetBboardPos Find out a billboard s position pfBboardAxis Specify the rotation or alignment axis pfGetBboard Axis Find out the rotation or alignment axis pfBboardMode Specify a billboard s rotation type pfGetBboardMode Find out a billboard s rotation type 141 Chapter 5 Nodes and Node Types 142 Example 5 12 demonstrates the construction of a pfBillboard node The code can be found in
238. ates to follow the eyepoint This is often simply a single texture mapped quadrilateral used to represent an object that has roughly cylindrical or spherical symmetry such as a tree or a puff of smoke respectively IRIS Performer supports billboards that can rotate about an axis for cylindrical objects or a point for spherical objects binning The action of the sort phase of libpf s cull traversal that segregates drawable geometry into major sections such as opaque and transparent before the per bin sorting based in the contents of associated pfGeoStates so that state changes can be reduced by drawing groups of similar geometry sequentially while still drawing semitransparent objects in the desired order within the frame bins The unique collections into which the cull traversal segregates drawable geometry The number of bins is defined by calls to pfChanBinSort and pfChanBinOrder Typical bins are those for opaque and transparent geometry where opaque objects are rendered first for superior image quality when using blended transparency bounding volume A convex region that encompasses a geometric object or a collection of such objects IRIS Performer pfGeoSets have axis aligned bounding boxes which are rectangular boxes whose faces are along the X Y or Z axes Each IRIS Performer pfGeode has a bounding sphere that contains the bounding box of each pfGeoSet in the pfGeode Performer group nodes have hierarchical bounding sph
239. ave some attributes indexed and others nonindexed Note Jibpf applications can include pfGeoSets in the scene graph with the pfGeode Geometry Node Table 10 1 lists a subset of the routines that manipulate pfGeoSets Table 10 1 pfGeoSet Routines Function Description pfNewGSet Create a new pfGeoSet pfDelete Delete a pfGeoSet pfCopy Copy a pfGeoSet pfGSetGState Specify the pfGeoState to be used pfGSetGStateIndex Specify the pfGeoState index to be used pfGSetNumPrims Specify the number of primitive items pfGSetPrimType Specify the type of primitive pfGSetPrimLengths Set the length of strip primitives Geometry Table 10 1 continued pfGeoSet Routines Function Description pfGSetAttr Set the attribute bindings pfGSetDrawMode Specify draw mode e g flat shading or wireframe pfGSetLineWidth Set the line width for line primitives pfGSetPntSize Set the point size for point primitives pfGSetHlight Specify highlighting type for drawing pfDrawGSet Draw a pfGeoSet pfGSetBBox Specify a bounding box for the geometry pfGSetIsectMask Specify an intersection mask for pfGSetIsectSegs pfGSetlsectSegs Intersect line segments with pfGeoSet geometry pfQueryGSet Determine the number of triangles or vertices pfPrint Print the pfGeoSet contents Primitive Types All primitives within a given pfGeoSet must be of the same type To set the type of all primitives in a pfGeoSet named gset call pfGSetPrimType gset
240. balance its cost a virtually free screen clear Technically it doesn t really clear the screen but rather allow you to set the z values in the framebuffer to be undefined Therefore use of this clear requires that every pixel on the screen be rendered every frame This clear is invoked with a pfEarthSky using the PFES_TAG option to pfESkyMode Refer to the pfEarthSky 3pf reference page for more detailed information Transparency There are two ways of achieving transparency on a RealityEngine blending and screen door transparency with multisampling Blended transparency using the IRIS GL blendfunction routine or the OpenGL g1BlendFunc equivalent can be used with or without Notes on Tuning for RealityEngine Graphics multisampling Blending doesn t increase the number of complex pixels but is expensive for complex pixels To reduce the number of pixels with very low alpha one can use a pfAlphaFunc that ignores pixels of low alpha such as alpha less than 3 or 4 This will slightly improve fill performance and probably not have a noticeable effect on scene quality Many scenes can use values as high as 60 or 70 without suffering degradation in image quality In fact for a scene with very little actual transparency this can reduce the fuzzy edges on textures that simulate geometry such as trees and fences that arise from MIP mapping Screen door transparency gives order independent transparent effects and is used
241. base Concerns Optimizing your databases can provide large performance increases libpr Databases The following tips will help you achieve peak performance when using libpr Minimize the number of pfGeoStates by sharing as much as possible Initialize each mode in the global state to match the majority of the database in order to set as little local state for individual pfGeoStates as possible Use triangle strips wherever possible they produce the largest number of polygons from a given number of vertices so they use the least memory and are drawn the fastest of the primitive types Use the simplest possible attribute bindings and use flat shaded primitives wherever possible If you re not going to need an object s attributes don t bind them anything you bind will have to be sent to the pipeline with the object Flat shaded primitives and simple attribute bindings reduce the transformation and lighting requirements for the polygon Note that the flat shaded triangle strip primitive renders faster than a regular triangle strip but you have to change the index by two to get the colors right that is you need to ignore the first two vertices when coloring See Attribute Bindings in Chapter 10 for more information Use nonindexed drawing wherever possible especially for independent polygon primitives and short triangle strips When building the database avoid fragmentation in memory of data to be rendered Minimize
242. best for culling since a GeoSet is the smallest culling unit and spatially localized GeoSets with few primitives are best for intersections Front Face Back Face One way to speed up intersection testing is to turn on PFTRAV_IS_CULL_BACK When this flag is enabled only front facing geometry is tested Enabling Caching Precomputing information about normals and projections speeds up intersections inside GeoSets For the best performance you should enable caching in GeoSets when you set the intersection masks with pfNodeTravMask If the geometry within a GeoSet is dynamic such as waves on a lake caching can cause incorrect results However for geometry that changes only rarely you can use pfGSetIsectMask to recompute the cache as needed Intersection Methods for Segments Normally when intersecting down to the primitive level each line segment is separately tested against each bounding volume in the scene graph and after passing those tests is intersected against the pfGeoSet bounding box Segments that intersect the bounding box are eventually tested against actual geometry When a pfSegSet has a spatially localized group of at least several line segments you can speed up the traversal by providing a bounding volume You can use pfCylAroundSegs to create a bounding cylinder for the segments and place a pointer to the resulting cylinder in the pfSegSet s bound field then OR the PFTRAV_IS_BCYL bit into the pfSegSet s
243. bflibpfdu pfdLoad File c pfdLoadFile pfdStoreFile pfdConvertFrom and pfdConvertTo exist only as a level of indirection to allow a user to manipulate all databases libpfdu Utilities for Creation of Efficient Performer Run Time structures regardless of format through a central API They are in fact merely a mechanism for creating an open environment for data sharing among the multitudes of 3 dimensional database formats In fact each of these routines merely determines via file type extension which database converter to load as a run time DSO and then calls the appropriate functionality from that converter s DSO All converters must provide API that is exactly the same as the corresponding libpfdu API with _EXT added to the routine names for example for medit files the suffix is _medit Note that multiple physical extensions can be mapped to one converter extension via calls to pfdAddExtAlias Several aliases are pre defined upon initialization of libpfdu For example VRML wrl files are mapped to Inventor iv so that the Open Inventor 2 1 loader can be used to import them It is also important to note that because each of these converters are unique entities that they each may have state that is important to their proper function Moreover their database format may allow for multiple IRIS Performer interpretations and so there exists API see Table 9 4 not only to initialize and exit database c
244. ble topics Alternatively use a World Wide Web browser to look at ftp sgigate sgi com pub Performer selected topics Electronic forum for discussions about IRIS Performer The info performer mailing list provides a forum for discussion of IRIS Performer including technical and non technical issues Subscription requests should be sent to info performer request sgi com Much like the comp sys sgi newsgroups on the Internet it isn t an official support channel but is monitored by several interested SGI employees familiar with the toolkit World Wide Web page Silicon Graphics maintains a public Web page for IRIS Performer at http www sgi com Technology Performer html This page can be accessed using a Web browser such as Netscape This guide errata and amendments may be made available through this page XXXV Chapier 1 ad Getting Acqu ainted With This chapter introduces you to some of the sample IRIS Performer IRIS Performer applications and databases Chapter 1 Getting Acquainted With IRIS Performer A complete sample application perfly as well as many short example programs are included with IRIS Performer This chapter explains how to use these applications so you can get acquainted with some of the features of IRIS Performer If you re already somewhat familiar with IRIS Performer or visual simulation in general you might want to skip ahead to the overview in Chapter 2 IRIS Performer Basics
245. blishing Company Inc 1993 A compilation of OpenGL reference pages e The OpenGL Porting Guide a Silicon Graphics publication shipped in IRIS InSight viewable on line format as part of the IRIS Developer Option Provides information on updating IRIS GL based software to use OpenGL Bibliography X Xt IRIS IM and Window Systems In conjunction with OpenGL you may wish to learn about the X window system the Xt Toolkit Intrinsics library and IRIS IM though note that if you use IRIS Performer s pfWindow routines windows are handled for you in that case you don t need to know about any of these topics For information on X Xt and Motif see the O Reilly X Window System Series Volumes 1 2 4 and 5 usually referred to simply as O Reilly with a volume number e Nye Adrian Volume One Xlib Programming Manual Sebastopol California O Reilly amp Associates Inc 1991 e Volume Two Xlib Reference Manual published by O Reilly amp Associates Inc Sebastopol California e Volume Four X Toolkit Intrinsics Programming Manual by Adrian Nye and Tim O Reilly published by O Reilly amp Associates Inc Sebastopol California e Volume Five X Toolkit Intrinsics Reference Manual published by O Reilly amp Associates Inc Sebastopol California For information on IRIS IM Silicon Graphics port of OSF Motif and on making your application interact well with the Silicon Graphics desktop se
246. boundary See Chapter 7 Frame and Load Control to learn more about frame rates phase and synchronization modes 63 Chapter 3 Building a Visual Simulation Application 64 Setting Up a Channel A channel is a rendering viewport into a pipe A pipe can have many channels within it but by default a channel occupies the full window of a pipe You can tell the channel to use a portion of the window using pfChanViewport pfChanViewport chan left right bottom top Channels support the standard viewing concepts such as eyepoint view direction field of view and near and far clipping planes For displays using multiple adjacent screens you can slave channels together to a single viewpoint You can also use channels to control scene management functions such as the switching of level of detail models based on graphics stress and pixel size See Using Channels in Chapter 4 to learn more about setting up channels Creating and Loading a Scene Graph Databases exist in a variety of formats IRIS Performer doesn t define a file format for databases instead it supports extensible run time scene definitions of sufficient generality to support many database formats Source code for several file importers is included with IRIS Performer the provided importers are described in Chapter 9 Importing Databases Creating a Database You can create a database with any modeler or write your own modeler using
247. bpf e The geometry and attribute definition objects of libpr 257 Chapter 9 Importing Databases 258 Structure and interpretation of the Database File Format In order to effectively convert a database into an IRIS Performer scene graph it is important to have a substantial understanding of several concepts related to the original database format e the parsing of the file based on the database format e the data types represented in the format and their IRIS Performer correspondence e the scene graph structure of the file if any e the method of graphics state definition and inheritance defined in the format Before trying to convert sophisticated 3 D database formats into IRIS Performer it is important to have a thorough grasp of how every structure in the format needs to affect how IRIS Performer performs its run time management of a scene graph However although it requires a great deal of understanding to convert complex behaviors of external formats into IRIS Performer it is still very straight forward to migrate basic structure geometry and graphics state into efficient IRIS Performer run time structures via the functionality provided in the IRIS Performer database builder pfdBuilder Scene Graph Creation using Nodes as defined in ibpf Creating an IRIS Performer scene graph requires a definite knowledge of the following IRIS Performer libpf node types pfScene pfGroup and pfGeode These nodes can be used t
248. bpr is a fundamental set of building blocks in much the same way that a graphics library is It doesn t impose a multiprocessing orientation nor is it targeted to any specific type of application its only goal is optimizing the use of SGI graphics hardware It can be used freely in conjunction with either the IRIS GL or the OpenGL graphics library The library has four basic components e high performance immediate mode geometry rendering e efficient management of Graphics Pipeline state e fast and flexible analytic intersection detection support e common low level programming utilities such as statistics gathering window management real time clocks and shared memory Some important features of libpr are that it e encapsulates graphics library state in objects e has a limited notion of hierarchy e doesn t extend or manage all graphics library functions e allows you to intermix graphics library and libpr calls freely e provides functionality not available in lower level graphics libraries e is an easy porting target for applications libpr provides highly optimized loops for rendering a wide variety of immediate mode geometric primitives like points lines triangles and triangle strips Geometry appearance is it textured lit transparent is determined by the current state of the Geometry Pipeline when the geometry is rendered Efficient management of this state is crucial for best performance To achieve the best performan
249. bpr pfWindows but have added support for handling the multiprocessed environment of libpf applications and fit into the libpf display hierarchy of pfPipes pfPipeWindows and pfChannels Additionally pfPipeWindows support the multiprocessing environment of libpf by having a separate copy of each pfPipeWindow in each pipeline process All of the windowness of pfPipeWindows really comes from the fact that there is a pfWindow internal to the pfPipeWindow Many of the basic support routines such pfPWinFullScreen and pfWinFullScreen have very similar functionality for pfWindows and pfPipeWindows However there are situations where pfPipeWindows are able to provide the same functionality in a much more efficient manner Management of dynamic window origin and size is one case where pfPipeWindows have a real advantage over pfWindows pfPipeWindows are able to take advantage of the multiprocessed libpf environment to always Using pfPipeWindows be able to return an accurate window size and origin relative to the window parent A process separate from the rendering process is notified by the window system of changes in the pfPipeWindow s size in an efficient manner without impacting the window system or the rendering process Further details regarding setting and querying window origin and size are discussed with pfWindows in Chapter 10 libpr Basics Note pfPWin routines expect a pfPipeWindow and the pfWin routines a pfWindo
250. buffer pass or fail status of the base geometry This bit is then used as a visibility determination rather than the Z buffer test for each of the layers which are rendered in bottom lowest visual priority to top highest visual priority order Z buffer updating is disabled during the stencil rendering operation and is restored when the pfLayer node has been completely rendered Stencil bit processing is the highest quality mode of pfLayer operation stress IRIS Performer stress processing is the closed loop feedback mechanism that monitors cull and draw times to determine how pfLODState range scale factors should be adjusted to compensate for system load in order to maintain a chosen frame rate subgraph A connected subset of a scene graph usually the set consisting of all descendents of a particular node texel Short for texture element a pixel of a texture texture mapping Displaying a texture as though it were the surface of a given polygon tile A section of a spatially subdivided database or a rectangular subregion of a larger texture image transformation Homogeneous 4x4 matrices that define 3D transformations some combination of scaling rotation and translation transition distance The distance at which one level of detail model is switched for another When fading or morphing between levels of detail the distance at which 50 of each model is rendered See level of detail traversals One o
251. c masks for different subgraphs of the scene this can be accomplished by calling pfNodeTravMask root PFSET_OR PFTRAV_SET_FROM_CHILD 0x0 which sets each node s mask by OR ing 0x0 with the current mask and the masks of the node s children Note that this traversal like that used to update node bounding volumes is unusual in that it propagates information up the graph from leaf nodes to root Discriminator Callbacks If you need to make a more sophisticated discrimination than node masks allow about when an intersection is valid IRIS Performer can issue a callback on each successful intersection and let you decide whether the intersection is valid in the current context 183 Chapter 6 Database Traversal 184 If a callback is specified in pfNodelIsectSegs then at each level where an intersection occurs for example with bounding volumes of libpf pfGeodes mode PFTRAV_IS_GEODE libpr GeoSets mode PFTRAV_IS_GSET or individual geometric primitives mode PFTRAV_IS_PRIM IRIS Performer invokes the callback giving it information about the candidate intersection The value you return from the callback determines whether the intersection should be ignored and how the intersection traversal should proceed If the return value includes the bit PFTRAV_IS_IGNORE the intersection is ignored The intersection traversal itself can also be influenced by the callback The traversal is subject to three possible fates
252. cal Instrumentation Engineers SPIE also has articles of interest to visual simulation developers in their conference proceedings Some of the interesting publications are e Vol 17 Photo Optical Techniques in Simulators April 1969 e Vol 59 Simulators amp Simulation March 1975 e Vol 162 Visual Simulation amp Image Realism August 1978 Survey Articles in Magazines e Aviation Week amp Space Technology January 17 1983 Special issue on visual simulation e Fischetti Mark A and Carol Truxal Simulating the Right Stuff IEEE Spectrum March 1985 pp 38 47 e Schacter Bruce Computer Image Generation for Flight Simulation IEEE Computer Graphics amp Applications October 1981 pp 29 68 e Schacter Bruce and Narendra Ahuja A History of Visual Flight Simulation Computer Graphics World May 1980 pp 16 31 e Tucker Jonathan B Visual Simulation Takes Flight High Technology Magazine December 1984 pp 34 47 Bibliography Internet Resources Answers to common questions Silicon Graphics maintains a publicly accessible directory of questions that developers often ask about IRIS Performer along with answers to those questions Each question and answer pair is provided in a file of its own named by topic To obtain any of these files use anonymous ftp to connect to sgigate sgi com then cd to the directory pub Performer selected topics and use Is to see a list of availa
253. ce state changes must be minimized and rendering loops must be free of decisions libpr employs two primary mechanisms for accomplishing this pfGeoSet and pfGeoState Geometry Geometry Simply put a pfGeoSet encapsulates 3D geometry while a pfGeoState encapsulates the appearance parameters known as pipeline state A pfGeoSet is drawn its vertices and other attributes are sent to the graphics library to be processed and ultimately rasterized on the screen A pfGeoState is applied its encapsulated state is used to configure the graphics library for a particular appearance such as lit textured and fogged A pfGeoSet can and usually does reference a pfGeoState thereby defining a both geometry and specific appearance attributes When the pfGeoSet is then drawn its associated pfGeoState is automatically applied first so that the geometry is rendered with the proper appearance Some specific libpr features and primitives discussed in this chapter are listed below e Fast rendering of geometry with a pfGeoSet e 3D Fonts with pfFont and pfString e Efficient state management with pfGeoStates and pfStates e Rendering effects with pfDecal for coplanar geometry pfFog pfLPointState and pfHighlight e Texturing with pfTexture pfTexEnv and pfTexGen e Lighting with pfLight pfLightModel and pfMaterial e 3D transformations with pfSprites and pfMatrix e Flexible and efficient immediate mode display lists with pfDispList e
254. center radius axis and half length as shown by the definition of the pfCylinder data structure typedef struct pfVec3 center float radius pfVec3 axis float halfLength pfCylinder A point p is in the cylinder with center c radius 1 axis a and half length h if p c a lt hand 1 p c a p c lt r Half spaces Planes A half space is defined by a plane with a normal pointing away from the interior It s represented by the pfPlane data structure typedef struct pfVec3 normal float offset pfPlane A point p is in the half space with normal n and offset d if p n lt d Frusta Unlike the other volumes a pfFrustum isn t an exposed structure You can allocate storage for a pfFrustum using pfNewFrust and you can set the frustum using pfMakePerspFrust or pfMakeOrthoFrust 409 Chapter 11 Math Routines 410 Creating Bounding Volumes The easiest and most efficient way to create a volume is to use one of the bounding operations The routines in Table 11 5 create a bounding volume that encloses other geometric objects Table 11 5 Routines to Create Bounding Volumes Routine Bounding Volume pfBoxAroundPts Box enclosing a set of points pfBoxAroundBoxes Box enclosing a set of boxes pfBoxAroundSpheres Box enclosing a set of spheres pfCylAroundSegs Cylinder around a set of segments pfSphereAroundPts Sphere around a set of points pfSphereAroundBoxes Sphere around a set of boxes p
255. cessing steps are made more complicated in practice by the performance inspired need to execute the operations in a multiprocessing environment Parallel processing is needed because users of this technology e need to perform hundreds to thousands of interpolations per character e desire several characters in animation simultaneously e prefer animation update rates of 30 or 60 Hertz e generate multiple independent displays from a single system Taken together these demands can require significant resources even when only vertex coordinates are interpolated When colors normals and texture coordinates are also interpolated and especially when shared vertex normals are recomputed the computational complexity is correspondingly increased The computational demands can be reduced when the rate of morphing is less than the image update rate The quality of the interpolated result can often be improved by applying a non linear interpolation operation such as the eased cosine curves and splines found useful in other applications of computer animation 27 Chapter 2 IRIS Performer Basics 28 Skeleton Animation A successful concept in computer assisted 2D animation systems is the notion of skeleton animation In this method you interpolate a defining skeleton and then position artwork relative to the interpolated skeleton In essence the skeleton defines a deformation of the original 2D plane and the original image is transformed by
256. ch pipeline pfPipe is independent in multiple pipe configurations the traversal and draw tasks are separate as are the libpr display lists that link them In contrast these pfPipes are controlled by the same application process and in many situations access the same shared scene definition Application Scene Pipeline 1 Traversal Cull Pipeline 0 Traversal Cull Draw Figure 4 2 Dual Graphics Pipeline Each of these stages can be combined into a single IRIX process or split into multiple processes pfMultiprocess for enhanced performance on multiple CPU systems Multiprocessing and multiple pipes are advanced topics that are discussed in Successful Multiprocessing With IRIS Performer in Chapter 7 Creating and Configuring a pfPipe pfMultipipe specifies the number of pfPipes desired pfMultiprocess specifies the multiprocessing mode used by all pfPipes These two routines are discussed further in Successful Multiprocessing With IRIS Performer in Chapter 7 75 Chapter 4 Setting Up the Display Environment 76 pfPipes and their associated processes are created when pfConfig is called They exist for the duration of the application After pfConfig the application can get handles to the created pfPipes using pfGetPipe The argument to pfGetPipe indicates which pfPipe to return and is an integer between 0 and numPipes 1 inclusive The pfPipe handle is then used for further configuration of the pfPipe
257. chines Under IRIX 6 2 and later if you want to use the extended MIPS 3 or MIPS 4 instruction set in a 32 bit application install the optional new 32 bit N32 version of IRIS Performer and use the n32 option to the compiler The old 32 bit new 32 bit and 64 bit versions of IRIS Performer can all be installed at the same time as each is installed in a separate directory usr lib usr lib32 and usr lib64 respectively Note IRIS GL does not exist in N32 or 64 bit form you must use OpenGL Using IRIS Performer From C IRIS Performer provides C bindings for all functions as well as C bindings Most of this guide does not include code examples in C however all sample programs are provided in the IRIS Performer distribution in both C and C versions The structure of a C program is largely identical to that of a C program for examples of IRIS Performer programs using the C API see the usr share Performer src pguide progs and apps directories for examples of equivalent C and C programs See Chapter 14 Programming with C for a discussion of the differences between programming using the C and C programming interfaces Chapter 4 Setting Up the Displ ay Environment This chapter describes how to create a display environment by configuring rendering pipelines channels and viewpoints Chapter 4 Using Pipes Setting Up the Display Environment libpf is a visual database p
258. ck Also notice that it is important to return the graphics library s state to the state at which it was in before the preNode callback was even made long pfdPostDrawReflMap pfTraverser trav void data F F F HF F texgen TX_S TG_OFF NULL texgen TX_T TG_OFF NULL return NULL libpf processes a visual database with a software rendering pipeline composed of application cull and draw stages The system of process callbacks allows you to insert your own custom culling and drawing functions into the rendering pipeline Furthermore these callbacks are invoked by the proper process when your IRIS Performer application is configured for multiprocessing By default IRIS Performer culls and draws all active pfChannels when pfFrame is called However you can specify cull and draw function callbacks so that pfFrame will cause IRIS Performer to call your custom functions instead These functions have the option of using the default IRIS Performer processing in addition to their own custom processing When multiprocessing is used the rendering pipeline works on multiple frames at once For example when the draw process is rendering frame n the cull process is working on frame n 1 and the application process is Process Callbacks working on frame n 2 This situation requires careful management of data so that data generated by the application is propagated to the cull process and then to the d
259. clipSeg pos simple test of pfTrilsectSeg Kel pfivec3s tri tr2 tr3 pfSeg seg float d 0 0f long i for i 0 i lt 30 i float alpha 2 0f drand48 0 5f float beta 2 0f drand48 0 5f float lscale 2 0f drand48 419 Chapter 11 Math Routines 420 float target long shouldisect MakeRandomVec3 trl MakeRandomVec3 tr2 MakeRandomVec3 tr3 MakeRandomVec3 pt1 pfCombineVec3 pt2 alpha tr2 beta tr3 pfCombineVec3 pt2 1 0f pt2 1 0f alpha beta pfMakePtsSeg amp seg ptl pt2 target seg length seg length lscale seg length isect pfTrilIsectSeg trl tr2 tr3 amp seg amp d shouldisect alpha gt 0 0f amp amp beta gt 0 0f amp amp alpha beta lt 1 0f amp amp lscale gt 1 0f if shouldisect if isect printf ERROR missed n else se ap De Be AssertFloatEq d target hit at wrong distance else if isect printf ERROR hit n simple test of pfCylContainsPt wa pfCylinder cyl pfVec3 pt pfVec3 perp pfSetVec3 cyl center 1 0f 10 0f 5 0f pfSetVec3 cyl axis 0 0f 0 0f 1 0f pfSetVec3 perp 1 0f 0 0f 0 0f cyl halfLength 2 0f cyl radius 0 5f pfCopyVec3 pt cyl center if pfCylContainsPt amp cyl pt printf center of cylinder not in cylinder n General Math Routine Example Progr
260. commands see Display Lists in Chapter 10 which describes the scene that is visible from a pfChannel The draw traversal simply traverses the display list and sends commands to the Geometry Pipeline to generate the image Traversing a pfDispList is much faster than traversing the database hierarchy because the pfDisp List flattens the hierarchy into a simple efficient structure In this way the cull traversal removes much of the processing burden from the draw traversal throughput greatly increases when both traversals are running in parallel Controlling and Customizing Traversals The result of the cull traversal is a display list of geometry to be rendered by the draw traversal What gets placed in the display list is determined by both visibility and by other user specified modes and tests pfChannel Traversal Modes The PFTRAV_CULL argument to pfChanTravMode modifies the culling traversal The cull mode is a bitmask that specifies the modes to enable it is formed by the logical OR of one or more of these tokens e PFCULL_VIEW e PFCULL_GSET 169 Chapter 6 Database Traversal 170 e PFCULL_SORT e PFCULL_IGNORE_LSOURCES Culling to the view frustum is enabled by PFCULL_VIEW Culling to the pfGeoSet level is enabled by PRCULL_GSET and can produce a tighter cull that improves rendering performance at the expense of culling time PFCULL_SORT causes the cull to sort geometry by state for example by texture or by
261. ct the geometry in the scene graph you must set intersection masks for the nodes in the scene graph and correspondingly in your search request 181 Chapter 6 Database Traversal 182 Setting the Intersection Mask pfNodeTravMask sets the intersection masks in a subgraph of the scene down through GeoSets For example pfNodeTravMask root PFTRAV_ISECT 0x01 PFTRAV_SELF PFTRAV_DESCEND PF_SET sets the intersection mask of all nodes and GeoSets in the scene graph to 0x01 A subsequent intersection request would then use 0x01 as the mask in pfNodelsectSegs A description of how to use this mask follows Specifying Different Classes of Geometry Databases can contain different classes of objects and only some of those may be relevant for a particular intersection request For example the wheels on a truck follow the ground even through a small pond therefore you only want to test for intersection with the ground and not with the water For a boat on the other hand intersections with both water and the lake bottom have significance To accommodate distinctions between classes of objects each node and GeoSet in a scene graph has an intersection mask This mask allows traversals such as intersections to either consider or ignore geometry by class For example you could use four classes of geometry to control tests for collision detection of a moving ship collision detection for a falling bowl
262. ctions by a single name in such cases an asterisk is used to indicate all the functions whose names start the same way For instance pfNew refers to all functions whose names begin with pfNew pfNewChan pfNewDCS pfNewESky pfNewGeode and so on Most code examples in this guide are written in C some are in C All code examples are available in both C and C forms in the source directory usr share Performer src pguide Bibliography Bibliography You should be familiar with most of the concepts presented in the first few books listed here notably Computer Graphics Principles and Practice and the IRIS GL or OpenGL books to make the best use of IRIS Performer and this programming guide Most of the other books listed here however delve into more advanced topics and are listed as further reading for those interested Information is also provided on electronic access to Silicon Graphics files containing answers to frequently asked IRIS Performer questions Computer Graphics For a general treatment of a wide variety of graphics related topics see e Foley J D A van Dam S K Feiner and J F Hughes Computer Graphics Principles and Practice 2nd Ed Reading Mass Addison Wesley Publishing Company Inc 1990 e Newman W M and R F Sproull Principles of Interactive Computer Graphics 2nd Ed New York McGraw Hill Inc 1979 For specific topics of interest to developers using IRIS Performer al
263. ctively The rate of turning and tilting is scaled by the distance of the cursor from the center of the simulation window that is no change of direction occurs when the cursor is at the center and full speed rotation occurs at the edges of the window If you want to maintain a steady velocity rather than accelerating hold down the middle mouse button to steer while using the left and right buttons to control the speed To stop tap the middle mouse button Trackball The trackball motion model provides a third option for controlling motion You can select this mode by pressing the right mouse button on the button marked Fly and selecting Trackball from the menu In trackball mode when you drag with the middle button the object rotates about its center as if it were attached to a large trackball that fills the screen That is dragging up and down causes rotation about the horizontal axis parallel to the screen and dragging left and right causes rotation about the vertical axis parallel to the screen By dragging with the left mouse you can translate the object in the direction you drag left right up or down By dragging with the right mouse you can translate the object in and out of the screen In all cases if you release the mouse button while dragging the motion continues on its own Chapter 1 Getting Acquainted With IRIS Performer Motion Using Paths There are other approaches to traveling through a scene than t
264. d 121 123 definition 519 shared 120 540 inst images performer_eoe 68 intensity of light points 237 internal API 482 interpolation MIP map 465 intersections 31 caching 460 masks 181 417 performance 460 pipeline definition 519 See also discriminator callbacks tests geometry sets 416 planes 416 point volume 412 segments 415 418 segment volume 415 triangles 416 volume volume 412 traversals See traversals I O asynchronous 391 handling 459 460 IRIS GL xxv documentation xxx functions afunction 337 blendfunction 476 finish 434 fogvertex 350 Imcolor 449 455 478 Imdef 348 349 mssize 369 pntsizef 236 RGBsize 369 shademodel 454 stencil 338 subtexload 345 swapbuffers 179 tevdef 342 texdef2d 342 343 texgen 347 winopen 370 zbsize 369 library and application suffix 40 porting from 40 IRIS IM 41 91 IRIS Image Vision Library 298 IRIS Inventor See Open Inventor IRIS Performer and C 70 applications compiling and linking 67 setting up 55 structure of 58 61 bibliography xxix xxxiv C API 481 accessor functions 481 header files 483 member functions 481 new 486 object creation 486 object deletion 486 public structs 482 reserved functions 482 static class data 495 subclassing 490 using both C and C API 488 using the C API with C 488 C API 481 differences between C and C error handling 391 features
265. d Control 220 Notice that when a stage is split into its own process the amount of time available for all stages increases For example in the case where the application cull and draw stages are 3 separate processes it is possible for total system performance to be tripled over the single process configuration Asynchronous Database Processing Many databases are too large to fit into main memory A common solution to this problem is called database paging where the database is divided into manageable chunks on disk and loaded into main memory when needed Usually chunks are paged in just before they come into view and are deleted from the scene when they are comfortably out of viewing range All this paging from disk and deleting from main memory takes a lot of time and is certainly not amenable to maintaining a fixed frame rate The solution supported by IRIS Performer is asynchronous database paging in which a process completely separate from the main processing pipeline s handles all disk I O and memory allocations and deletions To facilitate asynchronous database paging IRIS Performer provides the pfBuffer structure and the DBASE process DBASE Process The database or DBASE process is forked by pfConfig if the PFMP_FORK_DBASE bit was set in the mode given to pfMultiprocess The database process is triggered when the application process calls pfFrame and invokes the user defined callback set with pfDBaseFunc The
266. d after inputting all of the geometry and state found in a particular leaf node in the database Delete local data structures used to input geometry and graphics state Close the file Developing Custom Importers 10 Perform any optional optimization of the IRIS Performer scene graph 11 Optimizations might include calls to pfdFreezeTransforms pfFlatten or pfdCleanTree Return the pfGroup containing the entire IRIS Performer representation of the database file Steps 1 8 expand the function outline to the following extern pfNode pfdLoadFile_iim char fileName FILE iimFile pfdGeom polygon pfGroup root Performer has utility for finding and opening file if iimFile pfdOpenFile fileName NULL return NULL Clear builder from previous converter invocations pfdResetBldrGeometry pfdResetBldrState Call pfdBldrMode for any needed modes here Create polygon structure holds one N sided polygon where N is lt 300 polygon pfdNewGeom 300 Create pfGroup to hold entire database loaded from this file root pfNewGroup Specify state for geometry with no graphics state As well as default enables etc This routine should invoke pfdCaptureDefaultBldrState SetupDefaultGraphicsStatelIfTherelIsOne Do all the real work in parsing the file and converting into Performer ParselIMFile iimFile root po
267. d for creation of an accurate flight simulation visual with IRIS Performer The same is also true of marine and other vehicle simulations Using Channels Alternatively you can use pfChan ViewMat chan mat to create a 4x4 homogeneous matrix mat that defines the view coordinate system for channel chan The upper left 3x3 submatrix defines the coordinate system axes and the bottom row vector defines the origin of the coordinate system The matrix must be orthonormal or the results will be undefined You can construct matrices using tools in the libpr library The origin and heading pitch and roll angles or the view matrix create a complete view specification The view specification can locate the eyepoint frame of reference origin at any point in world coordinates The gaze vector the eye s Y axis can point in any direction The up vector the eye s Z axis can point in any direction perpendicular to the gaze vector You can query the system for the view and eyepoint direction values with pfGetChanView chan point dir or obtain the view matrix directly with pfGetChanViewMat chan mat The view direction can be modified by one or more offsets relative to the eyepoint frame of reference View offsets are useful in situations where several channels render the same scene into adjacent displays for a wider field of view or higher resolution Offsets are also used for multiple viewer perspectives such as pilot and copilot views
268. d in files and convert databases of unknown type This functionality is centered around the notion of a database converter A database converter is an abstract entity that knows how to perform some or all of a set of database format conversion functions with a particular database format Moreover converters must follow certain API guidelines for standard functionality such that they can be easily integrated into IRIS Performer in a run time environment without IRIS Performer needing any a priori knowledge of a particular converter s existence This run time integration is done through the use of dynamic shared object DSO libraries pfdLoadFile Loading Arbitrary Databases into Performer libpfdu provides the following general routines to operate on 3 D databases Table 9 2 libpfdu database converter functions Function Name Description pfdLoadFile Load a database file into an IRIS Performer scene graph pfdStoreFile Store a run time scene graph into a database file libpfdu Utilities for Creation of Efficient Performer Run Time structures Table 9 2 continued libpfdu database converter functions Function Name Description pfdConvertFrom Convert an external run time format into an IRIS Performer scene graph pfdConvertTo Convert an IRIS Performer scene graph into an external run time format The database loader utility library libpfdu provides a convenient function named pfdLoadFile that can import database files
269. d other state related functions like pfOverride Table 10 10 lists and describes the tokens Table 10 10 Rendering Attribute Tokens Attribute Token Description Apply Routine PFSTATE_LIGHTMODEL Lighting model pfApplyLModel PFSTATE_LIGHTS Light source definitions pfLightOn PFSTATE_FRONTMTL Front face material pfApplyMtl PFSTATE_BACKMTL Back face material pfApplyMtl PFSTATE_TEXTURE Texture pfApplyTex 341 Chapter 10 libpr Basics 342 Table 10 10 continued Rendering Attribute Tokens Attribute Token Description Apply Routine PFSTATE_TEXENV Texture environment pfApplyTEnv PFSTATE_FOG Fog model pfApplyFog PFSTATE_COLORTABLE Color table for pfGeoSets pfApplyCtab PFSTATE_HIGHLIGHT Definition of pfGeoSet pfApplyHlight highlighting style PFSTATE_LPOINTSTATE pfGeoSet light point definition pfApplyLPState PFSTATE_TEXGEN Texture coordinate generation pfApplyTGen definition Rendering attributes control which attributes are applied to geometric primitives when they re processed by the hardware All IRIS Performer attributes consist of a control structure definition routines and an apply function pfApply except for lights which are turned on Each attribute has an associated pfNew routine that allocates storage for the control structure When sharing attributes across processors in a multiprocessor application you should pass the pfNew routine a shared memory arena from which to allocate the str
270. d process needs access to the datapool it must first put the datapool in its address space by calling pfAttachDPool with the name of the datapool The datapool must reside at the same virtual address in all processes If the default choice of an address causes a conflict in an attaching process pfAttachDPool will fail To avoid this pfDPoolAttachAddr can be called before pfCreateDPool to specify a different address for the datapool Any attached process can allocate memory from the datapool by calling pfDPoolAlloc Each block of memory allocated from a datapool is assigned an ID so that other processes can retrieve the address using pfDPoolFind Managing Nongraphic System Tasks Once you ve allocated memory from a datapool you can lock the memory chunk not the entire pfDataPool by calling pfDPoolLock before accessing the memory This locking mechanism works only if all processes wishing to access the datapool memory use pfDPoolLock and pf DPoolUnlock After a piece of memory has been locked using pfDPoolLock any subsequent pfDPoolLock call on the same piece of memory will block until the next time a pfDPoolUnlock is called for that memory pfDataPools are pfObjects so call pfDelete to delete them Calling pfReleaseDPool unlinks the file used for the datapool it doesn t immediately free up the memory that was used or prevent further allocations from the datapool it just prevents processes from attaching to
271. declarations including macros for transparently casting a variable from one data type to another ANSI C requires that expressions used as function arguments be cast to match function prototypes Some routines therefore accept more than one type of argument with automatic casting between usable types For example a routine accepting a pfGroup as an argument can also take a pfSwitch In the code below switch is automatically cast to a pfGroup and geode is automatically cast to a pfNode by a macro within pf h pfGeode geode pfSwitch switch pfAddChild switch geode 61 Chapter 3 Building a Visual Simulation Application 62 lm Advanced Initializing and Configuring IRIS Performer Before you can set up a pipe you have to set up any areas of shared memory that you intend to use and you have to determine how many processors to use and in what configuration Initializing Shared Memory IRIS Performer uses shared memory to share data among the application the visibility cull traversal and the draw traversal all of which can run in parallel on different processors pfInit sets up the shared memory arena from which libpf objects are allocated The shared memory arena uses either swap space or a file in the directory specified by the environment variable PFTMPDIR For more information on shared memory arenas see Memory Allocation in Chapter 10 Initializing Processes pfConfig starts up multiple processes w
272. dels that come with IRIS Performer The images in this chapter were created using the Lightscape Visualization System available from Lightscape Technologies Inc in San Jose California For information on Lightscape software call 408 246 1155 Figure A 1 Simulated view of an atrium 499 Appendix A Image Gallery The image in Figure A 1 was created by A J Diamond Donald Schmitt and Company Toronto For information call 416 862 8800 The database that the image illustrates is part of the IRIS Performer software distribution Figure A 2 Another simulated view of the atrium The image in Figure A 2 was also created by A J Diamond Donald Schmitt and Company from the same database 500 Figure A 3 Simulated view of a castle The image in Figure A 3 was created by Advanced Graphics Applications Toronto For more information call 905 279 3838 The database that the image illustrates is part of the Friends of Performer software distribution 501 Appendix A Image Gallery Figure A 4 Simulated hallway view The image in Figure A 4 was created by A J Diamond Donald Schmitt and Company 502 Figure A 5 Simulated hotel lobby The image in Figure A 5 was created by Design Vision Inc Toronto For more information call 416 585 2020 503 Appendix A Image Gallery Figure A 6 Simulated waiting room The image in Figure A 6 was created by Digital Architecture Isao Nagaoka and Joe Hen
273. describes the IRIS Performer math routines Math routines let you create modify and manipulate vectors matrices line segments planes and bounding volumes such as spheres boxes and cylinders A basic set of mathematical operations is provided for setting and manipulating floating point vectors of length 2 3 and 4 The types of these vectors are pfVec2 pfVec3 and pfVec4 respectively The components of a vector are denoted by PF_X PF_Y PF_Z and PF_W with indices of 0 1 2 and 3 respectively In the case of 4 vectors the PF_W component acts as the homogeneous coordinate in transformations IRIS Performer supplies macro equivalents for many of the routines described in this section Inlining the macros instead of calling the routines can substantially improve performance Table 11 1 lists the routines what they do in mathematical notation and the macro equivalents where available for working with 3 vectors Most of the same operations are also available for 2 vectors and 4 vectors substituting 2 or 4 for 3 in the routine names The only operations not available for 2 vectors are vector cross products point transforms and vector transforms the only operations unavailable for 4 vectors are vector cross products and point transforms That is there are no such routines as pfCrossVec2 pfCrossVec4 pfXformPt2 pfXformPt4 or pfXformVec2 397 Chapter 11 Math Routines 398 Note For the d
274. differently in different views simply by applying a different pfColortable for each view By leaving the selection of color tables to the global state you can use a single call to switch color tables for an entire 349 Chapter 10 libpr Basics 350 scene In this way color tables can simulate time of day changes infrared imaging psychedelia and other effects pfNewCtab creates and returns a handle to a pfColortable As with other attributes you can specify which color table to use in a pfGeoState or you can use pfApplyCtab to set the global color table either in immediate mode or in a display list For an applied colortable to have effect colortable mode must also be enabled Fog A pfFog is created by calling pfNewFog As with any of the other attributes a pfFog can be referenced in a pfGeoState captured by a display list or invoked as an immediate mode command Fog is the atmospheric effect of aerosol water particles that occlude vision over distance The IRIS hardware can simulate this phenomenon in several different fashions A fog color is blended with the resultant pixel color based on the range from the viewpoint and the fog function pfFog supports several different fogging methods Table 10 14 lists the pfFog tokens and their corresponding actions Table 10 14 pfFog Tokens pfFog Token Action PFFOG_VTX_LIN Compute fog linearly at vertices PFFOG_VTX_EXP Compute fog exponentially at vertices e PFFOG
275. distributions of illumination load The processing burden of rendering a frame This includes both processing performed on the host CPU and in the graphics subsystem It is the maximum of these times sum in single process mode that is used to compute the system stress level for adjusting pfLODState values locked phase A style of frame overload processing where drawing may only begin on specific vertical retraces namely those that are an integer multiple of the basic frame rate morph attribute One of the collections of arrays of floating point data used in the pfMorph node s linear combination processing This process multiplies each element of each source array by a changeable weight value for that source array and sums the result of these products to produce the destination array morphing The mathematical manipulation of pfGeoSet data positions normals colors texture coordinates to cause a shape shifting behavior This is very useful for animated characters continuous terrain level of detail for smooth object level of detail and for a number of advanced applications In IRIS Performer morphing is provided by the pfMorph node multiple inheritance Deriving a class from more than one other class This is in contrast to single inheritance in which a type hierarchy is a tree IRIS Performer does not use multiple inheritance multithreaded In the context of IRIS Performer culling multithreading is an option for
276. draw stages even though those stages are in the same process The most common situation that calls for such a setup is multipass rendering when you want to cull only once but render multiple times With PFMP_CULL_DL_DRAW enabled pfCull generates a pfDispList that can be rendered multiple times by multiple calls to pfDraw Successful Multiprocessing With IRIS Performer Intersection Pipeline The intersection pipeline is a two stage pipeline consisting of the application and the intersection stages The intersection stage may be configured as a separate process by setting the PFMP_FORK_ISECT bit in the bitmask given to pfMultiprocess When configured as such the intersection process is triggered for the current frame when the application process calls pfFrame Then in the special intersection callback set with pfIsectFunc you can invoke any number of intersection requests with pfNodelsectSegs The intersection process is asynchronous so that if it does not finish within a frame time it does not slow down the rendering pipeline s Multiple Pipelines By default IRIS Performer uses a single pfPipe which in turn draws one or more pfChannels into one or more pfPipeWindows If you want to use multiple rendering pipelines as on two or three Geometry Pipeline Onyx RealityEngine systems use pfMultipipe to specify the number of pfPipes required When using multiple pipelines the PFMP_APPCULLDRAW and PFMP_APPCULL_DRAW modes are
277. e In IRIS GL the SUBLOAD format same as the FAST_DEFINE format on old versions of IRIS Performer can only be used on non MIPmapped textures The fast texture loading uses the IRIS GL subtexload and OpenGL glTexSubImage calls In IRIS GL subload sizes must be integral multiples of 32 Hint There are additional texture formatting modes that can improve texture performance Of most importance is the 16 bit texel internal formats These formats cause the resulting texels to have 16 bits of resolution instead of the standard 32 These formats can have dramatically faster texture fill performance and cause the texture to take up half the hardware texture memory Therefore they are strongly recommended and are used by default There are different formats for each possible number of components to give a choice of how the compression is to be done These formats are described in the pfTexFormat 3pf reference page There may also be formatting modes for internal or external image formats that IRIS Performer does not have a token for However the GL value can be specified Specifying GL values will make your application GL specific and may also cause future porting problems so it should only be done if absolutely necessary pfTextures also allow you to define a set of textures that are mutually exclusive should always be applied to the same set of geometry and thus that can share the same location in hardware texture memory With pfTexList tex
278. e Modes may also have associated values that allow a setting from a defined range Attributes are complex state structures that encapsulate a related collection of modes and values Attribute structures will not include in their definition an enable or disable as the enabling or disabling of a mode is orthogonal to the particular related attribute in use Rendering Modes libpr manages a subset of the rendering modes found in the graphics libraries In addition libpr abstracts certain concepts like transparency providing a higher level interface that hides the underlying implementation mechanism libpr provides tokens that identify the modes that it manages These tokens are used by pfGeoStates and other state related functions like pfOverride The following table enumerates the PFSTATE_ tokens of supported modes each with a brief description and default value Table 10 6 lists and describes the mode tokens Table 10 6 pfGeoState Mode Tokens Token Name Description Default Value PFSTATE_TRANSPARENCY Transparency modes PFTR_OFF PFSTATE_ALPHAFUNC Alpha function PFAF_ALWAYS PFSTATE_ANTIALIAS Antialiasing mode PFAA_OFF PFSTATE_CULLFACE Face culling mode PFCF_OFF PFSTATE_DECAL Decaling mode for PFDECAL_OFF coplanar geometry PFSTATE_SHADEMODEL Shading model PFSM_ GOURAUD PFSTATE_ENLIGHTING Lighting enable flag PF_OFF 335 Chapter 10 libpr Basics 336 Table 10 6 continued pfGeoState Mode Tokens Token Name D
279. e argument to pfAddChild The scope or area of influence of a pfLightSource is global and isn t affected by its location in the scene graph unless it is culled during the cull traversal If not culled it illuminates everything in the pfScene of which it is a member and doesn t affect anything outside the pfScene besides custom geometry rendered by the application in a channel draw callback A pfLightSource does inherit transformations and switch values from its parents in the scene graph Thus you can attach a light source to a moving object and easily turn it on and off Example 5 9 shows how you might configure the headlights of a moving car Example 5 9 Car Headlights as pfLightSource Nodes static pfNode initCarGeometry void pfDCS car pfNewDCS pfLightSource leftHeadlight pfNewLSource pfLightSource rightHeadlight pfNewLSource j Node Types Set white light color This isn t really necessary since pfLightSources are white by default m e pfLightColor leftHeadlight 1 0f 1 0f 1 0f pfLightColor rightHeadlight 1 0f 1 0f 1 0f Position headlights on front of car as local light sources pfLightPos leftHeadlight 1 0f 0 0f 0 0f 1 0f pfLightPos rightHeadlight 1 0f 0 0f 0 0f 1 0f Configure headlights as spotlights pointing in same direction as car Y direction Set the spotlights to have falloff of 1 and angular spread of 30 degrees my pf
280. e pfdConvertFrom or pfdConvertTo However users are free to add this functionality to the converters via compliant API and IRIS Performer s libpfdu will immediately recognize this functionality Also libpfdu traps access to non existent converter functionality and returns gracefully to the calling code while notifying the user that the functionality could not be found Finding and initializing a Converter When one of the general database converter functions is called it in turn calls the corresponding routine provided by the converter passing on the arguments it was given But the first time a converter is called a search occurs to identify the converter and the functions it provides This is accomplished as follows e Parse the extension what appears after the final in the filename This is referred to as EXT in the following bulleted items e Check to see if any alias was created for the EXT extension with pfdAddExtAlias If a translation is defined EXT is replaced with that extension e Check the current executable to see if the symbol pfdLoadFile_EXT is already defined i e if the loader was statically linked into the executable or a DSO was previously loaded by some other mechanism If not the search continues Generate a DSO library name to search for using on the extension prototype libpfEXT_ iglogl g so This means the following strings will be constructed based upon whether OpenGL or IRIS GL is
281. e scaled by 6 and alpha clamped at 1 pfLPStateVal lps PFLPS_TRANSP_EXPONENT 1 0f pfLPStateVal lps PFLPS_TRANSP_SCALE 6f pfLPStateVal lps PFLPS_TRANSP_CLAMP 1f Points are fogged as if 4 times closer than they really are pfLPStateVal lps PFLPS_FOG_SCALE 25f Compute true slant range from eye to points pfLPStateMode lps PFLPS_RANGE_MODE PFLPS_RANGE_MODE_TRUE Points are bidirectional with purple back color pfLPStateMode lps PFLPS_SHAPE_MODE PFLPS_SHAPE ODE_BI_COLOR pfLPStateBackColor lps 1 f 0 0f 1 f 1 0f Point shape is 15 horiz and 60 degrees vertical with no roll falloff of 1 and ambient intensity of 1 pfLPStateShape lps 15 0f 60 0f 0 0f 1 1f Set up pfGeoState gst pfNewGState arena Specify high quality transparency pfGStateMode gst PFSTATE_TRANSPARENCY PFTR_BLEND_ALPHA PFTR_NO_OCCLUDE pfGStateVal gst PFSTATE_ALPHAREF 0 0f pfGStateMode gst PFSTATE_ALPHAFUNC PFAF_GREATER pfGStateMode gst PFSTATE_ENFOG 0 pfGStateMode gst PFSTATE_ENLIGHTING 0 pfGStateMode gst PFSTATE_ENTEXTURE 1 pfGStateMode gst PFSTATE_ENLPOINTSTATE 1 pfGStateAttr gst PFSTATE_LPOINTSTATE lps 239 Chapter 8 Creating Visual Effects Configure texturing tgen pfNewTGen arena tex pfNewTex arena define USE_TEXTURE_MAPPING_FOR_DIRECTIONA
282. e these Silicon Graphics publications e IRIS IM Programming Guide e Indigo Magic User Interface Guidelines e Indigo Magic Desktop Integration Guide All three of these books are shipped in IRIS InSight viewable on line format as part of the IRIS Developer Option xxxi About This Guide xxxii Visual Simulation For information about visual simulation and the use of simulation systems in training and research see Rolfe J M and K J Staples eds Flight Simulation Cambridge Cambridge University Press 1986 Provides a comprehensive overview of visual simulation from the basic equations of motion to the design of simulator cabs optical and display systems motion bases and instructor operator stations Also includes a historical overview and an extensive bibliography of visual simulation and aerodynamic simulation references Rougelot Rodney S The General Electric Computer Color TV Display in Faiman M and J Nievergelt eds Pertinent Concepts in Computer Graphics Urbana Ill University of Illinois Press 1969 pp 261 281 This extensive report gives an excellent overview of the origins of visual simulation It shows many screen images of the original systems developed for various NASA programs and includes the first real time textured image This article provides the basis for understanding the historical development of computer image generation and real time graphics Schacter Bruce J ed Computer
283. e 4 1 pfPipes in Action main int i Initialize IRIS Performer pfinit Set number of pfPipes desired THIS MUST BE DONE BEFORE CALLING pfConfig E pfMultipipe NumPipes set multiprocessing mode pfMultiprocess ProcSplit Configure IRIS Performer and fork extra processes if configured for multiprocessing wy pfConfig Optional custom mapping of pipes to screens This is actually the reverse as the default ELA for i 0 i lt NumPipes i pfPipeScreen pfGetPipe i NumPipes i 1 set up optional DRAW pipe stage config callback pfStageConfigFunc 1 selects all pipes 77 Chapter 4 Setting Up the Display Environment 78 PFPROC_DRAW stage bitmask ConfigPipeDraw config callback Config func should be done next pfFrame pfConfigStage i PFPROC_DRAW TnitChannels trigger the configuration and opening of pfPipes and pfWindows i pfFrame Application s simulation loop while SimDone CALLBACK FUNCTIONS FOR PIPE STAGE INITIALIZATION void ConfigPipeDraw int pipe uint stage Application state for the draw process can be initialized here This is also a good place to do real time configuration for the drawing process if there is one There is no graphics state or pfState at this point so no rendering calls or pfApply call
284. e Description Range Default Value PFSTATE_ALPHAREF Set the alpha function 0 0 1 0 0 0 reference value Enable Disable pfEnable and pfDisable control certain rendering modes Certain modes do not have effect when enabled but require that other attribute s be applied Table 10 9 lists and describes the tokens and also lists the attributes required for the mode to become truly active Table 10 9 Enable and Disable Tokens Token Action Attribute s Required PFEN_LIGHTING Enable or disable pfMaterial lighting pfLight pfLightModel PFEN_TEXTURE Enable or disable pflexEnv texture pfTexture PFEN_FOG Enable or disable fog pfFog Graphics State Table 10 9 continued Enable and Disable Tokens Token Action Attribute s Required PFEN_WIREFRAME Enable or disable none pfGeoSet wireframe rendering PFEN_COLORTABLE Enable or disable pfColortable pfGeoSet colortable mode PFEN_HIGHLIGHTING Enable or disable pfHighlight pfGeoSet highlighting PFEN_TEXGEN Enable or disable pfTexGen automatic texture coordinate generation PFEN_LPOINTSTATE Enable or disable pfLPointState pfGeoSet light points By default all modes are disabled Rendering Attributes Rendering attributes are state structures that are manipulated through a procedural interface Examples include pfTexture pfMaterial and pfFog libpr provides tokens that enumerate the graphics attributes it manages These tokens are used by pfGeoStates an
285. e IRIS Performer Libraries 29 The libpf Visual Simulation Library 29 The libpr High Performance Rendering Library 32 The libpfdu Geometry Builder Library 36 The libpfdb Loader Library 37 Database Formats and IRIS Performer 38 Graphics Libraries 40 OpenGL 40 Porting From IRIS GL to OpenGL 40 The pfWindow Windowing Functions 41 Xand IRISIM 41 pfObjects and the Class Hierarchy 42 Inheritance Graph 43 User Data 45 pfDelete and Reference Counting 46 Copying Objects with pfCopy 49 Determining Object Type 50 Building a Visual Simulation Application 55 Overview 55 Setting Up the Basic Elements 61 Using IRIS Performer Header Files 61 Initializing and Configuring IRIS Performer 62 Setting Up a Pipe 63 Frame Rate and Synchronization 63 Setting Up a Channel 64 Creating and Loading a Scene Graph 64 Simulation Loop 65 Performance 66 Compiling and Linking IRIS Performer Applications 67 Setting Up the Display Environment 73 Using Pipes 73 The Functional Stages of a Pipeline 73 Creating and Configuring a pfPipe 75 Example of pfPipe Use 77 Using pfPipeWindows 79 Creating Configuring and Opening pfPipeWindow 79 pfPipeWindows in Action 90 Contents Using Channels 92 Creating and Configuring a pfChannel 92 Setting UpaScene 92 Setting Up a Viewport 93 Setting Up a Viewing Frustum 93 Setting Up a Viewpoint 95 Example of Channel Use 98 Using Multiple Channels 100 Using Channel Groups 105 5 Nodes and Node Types 111 Nodes 112 A
286. e Rate Management These specifications prevent the system from switching to a newly computed image until a display period of 1 20th second has passed from the time the previous image was displayed The frame rate remains fixed even when the Geometry Pipeline finishes its work in less time Fixed frame rate display therefore involves setting the desired frame rate and selecting one of the two fixed frame rate control modes Frame Skipping When multiple frame times elapse during the rendering of a single frame the system must choose which frame to draw next If the per frame display lists are processed in strict succession even after a frame overrun the visual image slowly recedes in time and the positional correlation between display and simulation is lost To avoid this problem only the most recent frame definition received by the draw process is sent to the Geometry Pipeline and all intervening frame definitions are abandoned This is known as dropping or skipping frames and is performed in both of the fixed frame rate modes Because the effects of variable frame rates phase variance and frame dropping are distracting you should choose a frame rate with care Steady frame rates are achieved when the frame time allows the worst case view to be computed without overload The structure of the visual database particularly in terms of uniform complexity density can be important in maximizing the system frame rate See Organizing a
287. e application or draw processes with pfOpenPWin and pfClosePWin Additionally pfConfigPWin can be re issued at any time from the application process to call the current window configuration function to dynamically open close and reconfigure pfPipeWindows The following example is taken from the distributed source code example file usr share Performer src pguide libpf C pipewin c and demonstrates the dynamic closing of a window from the application process in the simulation loop and the reuse of pfConfigPWin to reopen the window Example 4 6 Opening and Closing a pfPipeWindow main main simulation loop while Shared gt exitFlag wait until next frame boundary pfSync pfFrame Using pfPipeWindows Set view parameters for next frame UpdateView pfChanView chan Shared gt view xyz Shared gt view hpr Close pfPipeWindow if Shared gt closeWin 1 pfClosePWin Shared gt pw ct pfGetTime Shared gt closeWin 2 then wait two seconds and reconfig window else if Shared gt closeWin 2 amp amp pfGetTime ct gt 2 0f pfConfigPWin Shared gt pw Shared gt closeWin 3 pfNotify PFNFY_NOTICE PFNFY_PRINT OPEN You may want your windows to reside within a larger Motif interface and window hierarchy IRIS Performer supports this and allows you to run the Motif main loop in a separate process so that you can m
288. e at a certain distance may not be visible at that same distance in dense fog Implementing more sophisticated culling requires knowledge of visibility conditions and control over the cull traversal The cull traversal can be controlled through traversal masks which are described in the section titled Controlling and Customizing Traversals Knowing whether an object is visible requires either prior information about the spatial organization of a database such as cell to cell visibilities or run time testing such as computing line of sight visibility LOS You can compute simple LOS visibility by intersecting line segments that start at the eyepoint with the database See the Intersection Traversal section of this chapter Sorting the Scene During the cull traversal a pfChannel can rearrange the order in which pfGeoSets are rendered for improved performance and image quality It does this by binning and sorting Binning is the act of placing pfGeoSets into specific bins which are rendered in a specific order IRIS Performer provides two default bins one for opaque geometry and one for blended transparent geometry The opaque bin is drawn before the transparent bin so transparent Cull Traversal surfaces are properly blended with the background scene Applications are free to add new bins and specify arbitrary bin orderings Sorting is done on a per bin basis pfGeoSets within a given bin are sorted by a specific criteri
289. e chains have been explored pfDelete returns a boolean indicating whether it successfully deleted the first object or not Example 2 2 illustrates the use of pfDelete with libpr Example 2 2 Using pfDelete with libpr Objects pfGeoState gstate0 gstatel pfMaterial mtl pfGeoSet gset gstate0 pfNewGState arena initial ref count is 0 47 Chapter 2 IRIS Performer Basics 48 gset pfNewGSet arena initial ref count is 0 mtl pfNewMtl arena initial ref count is 0 Attach mtl to gstate0 Reference count of mtl is incremented pfGStateAttr gstate0 PFSTATE_FRONTMTL mtl Attach mtl to gstatel Reference count of mtl is incremented pfGStateAttr gstatel PFSTATE_FRONTMTL mtl Attach gstate0 to gset Reference count of gstate0 is incremented pfGSetGState gset gstate0 This deletes gset gstate0 but not mtl since gstatel is still referencing it pfDelete gset Example 2 3 illustrates the use of pfDelete with libpf Example 2 3 Using pfDelete Q with libpf Objects pfGroup group pfGeode geode pfGeoSet gset group pfNewGroup initial parent count is 0 geode pfNewGeode initial parent count is 0 gset pfNewGSet arena initial ref count is 0 Attach geode to group Parent count of geode is incremented pfAddChild group geode Attach gset to geode Reference count
290. e function pfdLoadFile_dwb to load Designer s Workbench files into IRIS Performer run time data structures AutoCAD DXF Format The DXF format originated with Autodesk s AutoCAD database modeling system The version recognized by the pfdLoadFile_dxf database importer is a subset of ASCII Drawing Interchange Format DXF Release 12 The binary version of the DXF format also known as DXF isn t supported Source code for the importer is in the file usr share Performer srcflibflibpfdb libpfdxf pfdxf c pfdLoadFile_dxf was derived from the DXF to DKB data file converter developed and placed in the public domain by Aaron A Collins 277 Chapter 9 Importing Databases The image in Figure 9 3 shows a DXF model of the famous Utah teapot This model was loaded from DXF format using the pfdLoadFile_dxf database importer Figure 9 3 The Famous Teapot in DXF Form The DXF format has an unusual though well documented structure The general organization of a DXF file is 1 HEADER section with general information about the file 2 TABLES section to provide definitions for named items including m LTYPE the line type table a LAYER the layer table a STYLE the text style table a VIEW the view table a UCS the user coordinate system table 278 Description of Supported Formats a VPORT the viewport configuration table a DIMSTYLE the dimension style table a APPID the application identification table 3 BLOCKS section
291. e intersection traversal all provide a mechanism for registered process callbacks These are user functions that are invoked at the beginning of the indicated processing stage and in the process handling the traversal projective texturing A texture technique that allows texture images to be projected onto polygons in the same manner as a slide or movie projector would exhibit keystone distortion when images are cast non obliquely onto a wall or screen This effect is perfect for projected headlights and similar lighting effects prune To eliminate a node from further consideration during culling punch through Decreasing the rate at which intensely luminous objects such as light points are attenuated as a function of distance Normal fogging is inappropriate for such objects because up close they are actually much brighter than can be rendered given the dynamic range of the frame buffer and raster display devices reference counting The counter within each pfObject and pf Memory object that keeps track of how many other data structures are referencing the particular instance The primary purpose is to indicate when an object may be safely deleted because it is no longer referenced rendering pipeline An IRIS Performer rendering pipeline represented in an application by a pfPipe Typically a rendering pipeline has three stages APP CULL and DRA W These stages may be handled in separate processes or combined into one or two pr
292. e objects that are not visible Usually this refers to discarding objects located outside the current viewing frustum This is done by comparing the bounding volume of these database objects with the six planes that bound the frustum Objects completely outside may be safely discarded See also occlusion culling data fusion IRIS Performer s ability to read data in a variety of different database formats and convert it into the internal IRIS Performer scene database format Further the ability of these different formats to provide special run time behavior via callback functions or node subclassing and to have these different data formats all active in their native modes simultaneously database paging Loading databases from disk or network into memory for traversal during real time simulation Database paging is implicit in large area simulations due to the huge database sizes inherent in any high resolution earth database A frequent component of database paging is texture paging in which new textures are downloaded to the graphics system at the same time new geometry is loaded from disk debug libraries IRIS Performer libraries compiled with debugging symbols left in are known as debug libraries These libraries provide greater and more accurate stack trace information when examining core dumps such as during application development decal geometry Objects that appear above other objects in pfLayer geometry Ina runways and
293. e passed instead e g pfMatrix ident ident makeIdent glLoadMatrix ident mat When compiled with C IRIS Performer supports three usages of the API 1 Pure C API This is the default style of usage 2 Pure C API This can be achieved by defining the token PF_CPLUSPLUS_API to be 0 e g by adding the line define PF_CPLUSPLUS_API 0 in source files before they include any IRIS Performer header files In this mode all data types are the same as when compiling with C 3 C API and C API This mode can be enabled by defining the token PF_C_API to be 1 e g by adding the line define PF_C_API 1 in source files before they include any IRIS Performer header files In this mode both C and C functions are available and data types are C See the section below concerning passing certain data types Typedefed Arrays vs Structs In the C API the pfVec2 pfVec3 pfVec4 pfMatrix and pfQuat data types are all typedefed arrays In the C API they are all structs When converting C code to use the C API or when compiling CAPI code with both APIs enabled be sure to change routines in your code that pass objects of these types In the C API you almost always want to pass arguments of these types by reference rather than by value Porting from C API to C API For example the C API routine void MyVectorAdd pfVec2 dst pfVec2 vl pfVec2 v2 dst 0 v1 0 v2 0 dst 1 vl 1 v2 1 o
294. e provided node Additionally pfFrameStats has special support for the multiprocessed environment of libpf and ensures that the statistics operations are all done in the correct process All modifying of a pfFrameStats structure including enabling and disabling of classes printing and copying should all be done in the application process pfDrawFStats and pfDrawChanStats can be called in either the application process or the draw process Statistics Rules of Use Enabling and disabling of statistics and setting of modes and attributes on a statistics structure should always be done in the application process the settings will automatically be passed down the process pipeline To enable classes of statistics on a pfFrameStats call pfFStatsClass and provide a statistics structure a bitmask of statistics enabling tokens tokens with STATS_EN in their names for the desired classes and the token PFSTATS_ON Obtain the statistics structure from the desired channel by calling pfGetChanFStats For example Collecting and Accessing Statistics in Your Application pfFStatsClass pfGetChanFStats chan PFFSTATS_ENCULL PFFSTATS_ENDB PFSTATS_ON enables the cull statistics and database statistics classes leaving settings alone for any other classes Notice that the classes specific to pfFrameStats have a PFFSTATS_ prefix You can use PFSTATS_SET instead of PFSTATS_ON to enable only the specified classes disabling a
295. e that can be selectively suppressed pfNotifyLevel sets the notification level to one of the values listed in Table 10 26 Table 10 26 Error Notification Levels Token Meaning PFNFY_ALWAYS Always print regardless of notify level PFNFY_FATAL Fatal error PFNFY_WARN Serious warning PFNFY_NOTICE Warning PFNFY_INFO Information and floating point exceptions PFNFY_DEBUG Debug information PFNFY_FP_DEBUG Floating point debug information The environment variable PFNFYLEVEL can be set to override the value specified in pfNotifyLevel Once the notification level is set via PFNFYLEVEL it can not be changed by an application Once the notify level is set only those messages with a priority greater than or equal to the current level are printed or handed off to the user function Fatal errors cause the program to exit unless the application has installed a handler with pfNotifyHandler Setting the notification level to PFNFY_FP_DEBUG has the additional effect of trapping floating point exceptions such as overflows or operations on Managing Nongraphic System Tasks invalid floating point numbers It may be a good idea to use a notification level of PFNFY_FP_DEBUG while testing your application so that you will be informed of all floating point exceptions that occur File Search Paths IRIS Performer provides a mechanism to allow referencing a file via a set of path names Applications can create a search list of path
296. e tires just knowing that a tire is picked is not sufficient for further processing perfly The application distributed with IRIS Performer that serves as a demonstration program installed in usr sbin as well as a programming example found in usr share Performer src sample apps C and usr share Performer src sample apps C for the C and C versions respectively phase An application s synchronization mode defining how the system behaves if the processing and drawing time for a given frame extends past the time allotted for a frame See also locked phase and floating phase pipe Used to refer to both an IRIS Performer software rendering pipeline and to a graphics hardware rendering pipeline suchas a RealityEngine See rendering pipeline pitch In the context of X axis to the right Y axis forward and Z axis up then pitch is rotation about the X axis This is the rotation that would raise or lower the nose of an aircraft Also see Euler angles popping The term for the highly noticeable instantaneous switch from one level of detail to the next when morph or blend transitions are not used This problem is distracting and should be eliminated in high quality simulation applications process callbacks The mechanism through which a developer takes control of processing activities in the various IRIS Performer traversals and major processing stages the application traversal the cull traversal the draw traversal and th
297. e update rate Fixed Frame Rate Control Assume that the overrun frame in Figure 7 1 completes processing during the next refresh period as shown After the overrun frame the simulation is still running at the chosen 20 Hz rate and is updating at every third vertical retrace If a new image is displayed at the next refresh its start time lags by 1 60th of a second and therefore it is out of phase by that much Subsequent images are displayed when the refresh count modulo three is one As the simulation continues and additional extended frames occur the phase continues to drift This mode of operation is called floating phase as shown by the frame in Figure 7 1 labeled Floating Use pfPhase PFPHASE_FLOAT to select floating phase frame control The alternative to displaying a new image out of phase is to display the old image for the remainder of the current update period then change to the new image at the normal time This locked phase extends each frame overrun to an integral multiple of the selected frame time making the overrun more evident but also maintaining phase throughout the simulation This timing is shown by the frame in Figure 7 1 labeled Locked Although this mode is the most restrictive it is also the most desirable in many cases Use pfPhase PFPHASE_LOCK to select phase locked frame control For example a 20 Hz phase locked frame rate is selected by specifying pfPhase PFPHASE_LOCK pfFrameRate 20 0f Fram
298. e used to 25 Chapter 2 IRIS Performer Basics 26 scale the colors of objects in the database in order to implement complex lighting models such as Phong shading with high performance You can use this method to provide elaborate lighting environments in systems where per pixel shading calculations would not otherwise be available Projective Texture You can also use texture mapping to project images such as aircraft landing lights and vehicle headlights into images These projective texture techniques when combined with the ability to use Z buffer contents to texture images allow the generation of real time images with true 3D cast shadows Character Animation Some interactive applications include animated characters as well as scenery and objects Character animation is a complex topic with its own needs and techniques Morphing Terrain Level of Detail in Chapter 7 describes the simplest active database methodology for continuous terrain level of detail processing based on interpolation between two elevations for vertices a process also known as morphing Advanced Onyx RealityEngine real time image generation hardware is capable of the interpolation of vertex position colors normal vectors and texture coordinates between two versions of a model using the IRIS Performer pfMorph node Morphing can be used to fill in motion between a start position and an end position for an object or in its fully generalized for
299. ead ith Vertex into local data structure polygon gt coords i 0 GetNextVertexFloat polygon gt coords i 1 GetNextVertexFloat polygon gt coords i 2 GetNextVertexFloat Read texture coord for ith vertex if any if polygon gt tbind PFGS_PER_VERTEX polygon gt texCoords i 0 GetNextTexFloat polygon gt texCoords i 1 GetNextTexFloat Read normal for ith Vertex if normals bound if polygon gt nbind PFGS_PER_VERTEX polygon gt norms i 0 polygon gt norms i 1 polygon gt norms i 2 GetNextNormFloat GetNextNormFloat GetNextNormFloat 263 Chapter 9 Importing Databases Read only one normal per prim if necessary else if polygon gt nbind PFGS_PER_PRIM amp amp i 0 polygon gt norms 0 0 GetNextNormFloat polygon gt norms 0 1 GetNextNormFloat polygon gt norms 0 2 GetNextNormFloat Get Color for the ith Vertex if color bound if polygon gt cbind PFGS_PER_VERTEX polygon gt colors i 0 GetNextColorFloat polygon gt colors i 1 GetNextColorFloat a polygon gt colors i 2 GetNextColorFloat F Get one color per prim if necessary else if polygon gt cbind PFGS_PER_PRIM amp amp 1 0 polygon gt colors 0 0 GetNextColorFloat polygon gt colors 0
300. eadily available technique and many special purpose approaches to visual simulation have been tried For example the NASA Kennedy Space Center newspaper Spaceport News described the Apollo 7 astronaut training visual simulator this way on March 28 1968 Each simulator consists of an instructor s station crew station computer complex and projectors to simulate the stages of a flight Engineers serve as instructors instruments keeping them informed at all times of what the pilot is doing Through the windows infinity optics equipment duplicates the scenery of space The main components of a typical visual display for each window includes a 71 centimeter fiber plastic celestial sphere embedded with 966 ball bearings of various sizes to represent the stars from the first through fifth magnitudes a mission effects projector to provide earth and lunar scenes and a rendezvous and docking projector which functions as a realistic target during maneuvers Since such beginnings the sense of reality that visual simulation systems can provide has advanced significantly due both to advances in hardware and software and to a greater understanding of human perceptions 1 In recognition of the ingenuity of this system IRIS Performer includes a star database with the locations and magnitudes of the 3010 brightest stars as seen from earth View the file usr share Performer data 3010 star with perfly while contemplating the
301. ears three dimensional For more information on billboards see pfBillboard Nodes in Chapter 5 To determine if the current graphics platform has fast texture mapping look for a PFOFTR_FAST return value from pfFeature PFOQFTR_TEXTURE amp ret pfAlphaFunc with a function PFAF_GEQUAL and a reference value greater than zero can be used whenever transparency is used to remove pixels of low contribution and avoid their expensive processing phase Special Coding Tips For maximum performance routines that make extensive use of the IRIS Performer linear algebra routines should use the macros defined in prmath h to allow the compiler to in line these operations Use single rather than double precision arithmetic where possible and avoid the use of short integer data in arithmetic expressions Append an f to all floating point constants used in arithmetic expressions BAD In this example values in both of the expressions involving the floating point variable x are promoted to double precision when evaluated float x if x lt 1 0 x x 2 0 GOOD In this example both of the expressions involving the floating point variable x remain in single precision mode because there is an f appended to the floating point constants float x if x lt 1 0 x x 2 0f Performance Measurement Tools Performance Measurement Tools Performance measurement tools can help you track the progress of
302. ecific Guidelines for Optimizing Performance Balance the database hierarchy with the scene complexity the depth of the hierarchy the number of pfGeoStates and the depth of culling See Balancing Cull and Draw Processing with Database Hierarchy on page 462 for details pfNodes that have significant evaluation in the cull stage include pfBillboards pfLightPoints pfLightSources and pfLODs Draw Process Tips Here are some suggestions specific to the draw process Minimize host work done in the draw process before the call to pfDraw Time spent before the call to pfDraw is time that the graphics pipeline is idle Any graphics library or X input processing or mode changes should be done after pfDraw to take effect the following frame Use only one pfPipe per hardware graphics pipeline and preferably one pfPipeWindow per pfPipe Use multiple channels within that pfPipeWindow to manage multiple views or scenes It s fairly expensive to simultaneously render to multiple graphics windows on a single hardware graphics pipeline and is not advisable for a real time application Pre define and pre load all of the textures in the database into hardware texture memory by using a pfApplyTex function on each pfTexture You can do this texture applying in the pfConfigStage draw callback or for multipipe applications to allow parallelism the pfConfigPWin callback This approach avoids the huge performance impact that result
303. ector s bulb and whose view plane is the slide holder and the projected texture map is the slide A pfLightSource s frustum is set with pfLSourceAttr with the PFLS_PROJ_FRUSTUM identifying token In addition to a frustum projected texturing requires a texture map supplied with pfLSourceAttr with PFLS_PROJ_TEX identifying token This texture map can be anything but is usually a texture with identical intensity and alpha components which represent the soft edged circle of a spotlight Colored spotlights are simulated by coloring the pfLightSource with pfLSourceColor rather than coloring the texture map Opera lighting where an actual color slide is projected onto the set is simulated with a Spotlights and Shadows texture map consisting of red green blue and alpha components this is supported only if the pfLightSource is the only one that is projecting a texture Shadows do not require the application to supply a texture map rather one is automatically created by IRIS Performer However the size of the shadow map has an important effect on the quality of the shadows and may be set with the PFLS_SHADOW_SIZE token to pfLSourceVal For high quality shadows the pfLightSource s frustum must encompass the entire scene that is to be shadowed as tightly as possible If the frustum s field of view or far to near clipping plane ratio becomes too large the shadows will become blocky and incorrect One way to improve shadow quali
304. ecursively free this node if it s no longer referenced pfDelete scene pfGroup In addition to inheriting the pfNode attributes described in the pfNode section of this chapter a pfGroup also maintains a list of zero or more child nodes that are accessed and manipulated using group operators Children of a pfGroup can be either branch or leaf nodes Traversals process the children of a pfGroup in left to right order Table 5 2 lists the pfGroup functions with a description and a visual interpretation of each Table 5 2 pfGroup Functions Function Name Description Diagram pfAddChild group child Appends child to the list for group O child whose place in the list is index pfInsertChild group index child Inserts child before the index 2 ose pfRemoveChild group child Detaches child from the list and shifts the list to fill al the vacant spot Returns1 0 0 if child was removed o Returns 0 if child was not found in the list Note e o that the removed node is only detached not deleted pfGetNumChildren group Returns the number of t y children in group 117 Chapter 5 Nodes and Node Types 118 pfGroup nodes can organize a database hierarchy either logically or spatially For example if your database contains a model of a town a logical organization might be to group all house models under a single pfGroup However this kind of organization is less ef
305. ed The pfStats Data Structure The pfStats data structure contains four statistics buffers one for current statistics one for previous statistics one for cumulative statistics and one for averages If you re using libpf calls to have IRIS Performer keep track of statistics for you you should always look at the previous stats buffer the current stats buffer is kept in a state of flux and if you look at it you re likely to find meaningless numbers there If on the other hand you re using libpr and keeping track of your own statistics the current stats buffer does contain accurate information Statistics Examples This section contains some examples of statistics calls Setting statistics class enables and modes Set all stats class enables on a pfStats to their default values pfStatsClass stats PFSTATS_ALL PFSTATS_DEFAULT Set all modes for the PFSTATS_GFX class on a pfFrameStats to their default values pfFStatsClassMode fstats PFSTATS_GFX PFSTATS_ALL PFSTATS_ DEFAULT Note that pfStatsClassMode takes a class name as its class specifier second argument and not a bitmask However you can use PFSTATS_CLASS to refer to the modes of all classes pfFStatsClassMode fstats PFSTATS_MODE PFSTATS_ALL PFSTATS_DEFAULT 443 Chapter 12 Statistics 444 sets all modes of all pfStats classes to their default values For pfFrameStats classes there is PFFSTATS_CLASS Set the
306. ed to intersection traversal These nodes impose spatial partitioning on the subgraph beneath them which can dramatically improve the performance of intersection traversals Note Subgraphs under pfDCS pfLOD pfSwitch and pfSequence nodes are not partitioned so intersection traversals of these subgraphs will not be affected Use intersection caching For static objects enable intersection caching at initialization first call pfNodeTravMask specifying intersection traversal PFTRAV_ISECT and then include PFTRAV_IS_CACHE in the mode for intersections You can turn this mode on and off for dynamic objects as appropriate Use intersection masks on nodes to eliminate large sections of the database when doing intersection tests Note that intersections are sproc safe in the current version of IRIS Performer you can check intersections in more than one process Bundle segments for intersections with bounding cylinders You can pass as many as 32 segments to each intersection request If the request contains more than a few segments and if the segments are close together the traversal will run faster if you place a bounding cylinder around the segments using pfCylAroundSegs and pass that bounding cylinder to pfNodelsectSegs The intersection traversal will use the cylinder rather than each segment when testing the segments against the bounding volumes of nodes and pfGeoSets Specific Guidelines for Optimizing Performance Data
307. efined 528 texturing overview 342 performance cost 454 476 RealityEngine graphics 477 representing complex objects 465 tile defined 528 time of day clockclocks available types 34 timing 34 tokens APP_CULL_DRAW 467 PF_MAX_LIGHTS 349 PF_OFF 335 336 PFAA_OFF 335 PFAF_ALWAYS 335 PFAF_GREATER 337 PFBOUND_STATIC 124 PFCF_BACK 339 PFCF_BOTH 339 PFCF_FRONT 339 PFCF_OFF 335 339 558 PFCHAN_EARTHSKY 106 PFCHAN_FOV 106 PFCHAN_LOD 106 PFCHAN_NEARFAR 106 PFCHAN_SCENE 106 PFCHAN_STRESS 106 PFCHAN_SWAPBUFFERS 106 PFCHAN_VIEW 106 PFCHAN_VIEW_OFFSETS 106 PFCULL_GSET 169 170 PFCULL_IGNORE_LSOURCES 136 170 PFCULL_SORT 170 452 PFCULL_VIEW 169 170 PFDECAL_BASE_STENCIL 338 339 PFDECAL_LAYER_ STENCIL 339 PFDECAL_OFF 335 339 PFDL_RING 355 PFDRAW_OFF 170 PFDRAW_ON 170 PFEN_COLORTABLE 341 PFEN_FOG 340 PFEN_HIGHLIGHTING 341 PFEN_LIGHTING 340 PFEN_LPOINTSTATE 341 PFEN_TEXGEN 341 PFEN_TEXTURE 340 PFEN_WIREFRAME 341 PFES_BUFFER_CLEAR 231 PFES_FAST 234 PFES_GRND_FAR 232 PFES_GRND_HT 231 PFES_GRND_NEAR 232 PFES_SKY 235 PFES_SKY_CLEAR 235 PFES_SKY_GRND 231 235 PFFB_ACCUM_ALPHA SIZE 369 PFFB_ACCUM_BLUE_SIZE 369 PFFB_ACCUM_GREEN_SIZE 369 PFFB_ACCUM_RED SIZE 369 PFFB_ALPHA SIZE 368 PFFB_AUX_BUFFER 368 PFFB_BLUE_SIZE 368 PFFB_BUFFER_SIZE 368 PFFB_DEPTH_SIZE 368 PFFB_DOUBLEBUFFER 368 PFFB_GREEN_SIZE 368 PFFB_RED_SIZE 368 PFFB_RGBA 368 PFFB_S
308. egSet mask Masks Mask Mask Mask Traversee pfNodeTrav pfNodeTrav pfNodeTrav pfNodeTrav Masks Mask Mask Mask Mask pfGSetlsect Mask Scene Graph Hierarchy Scene Graph Hierarchy A visual database also known as a scene contains state information and geometry A scene is organized into a hierarchical structure known as a graph The graph is composed of connected database units called nodes Nodes that are attached below other nodes in the tree are called children Children belong to their parent node Nodes with the same parent are called siblings Database Traversals The scene hierarchy supplies definitions of how items in the database relate to one another It contains information about the logical and spatial organization of the database The scene hierarchy is processed by visiting the nodes in depth first order and operating on them The process of visiting or touching the nodes is called traversing the hierarchy The tree is traversed from top to bottom and from left to right IRIS Performer implements several types of database traversals including application clone cull delete draw flatten and intersect These traversals are described in more detail later in this chapter The principal traversals application cull draw and intersect all use a similar traversal mechanism that employs traversal masks and callbacks to control the traversal When a node is visited during the traversal processing is p
309. ency if it shows too many very short strips you may want to go back and restructure your database As a general rule of thumb consider a very short strip to be one that s less than 4 triangles long but that number may vary depending on your database To enable these statistics on a channel do pfFStatsClass pfGetChanFStats chan PFSTATS_ENGFX PFSTATS_ON A summary of the graphics state operations including loading of textures and of the number of operations that have recently been performed on the transformation stack also part of the GFX stats class the number of libpf nodes being drawn in several categories including billboards light points and geodes plus the number of nodes of each type evaluated in the application and cull stages which can be enabled with pfFStatsClass pfGetChanFStats chan PFSTATS_ENDB PFSTATS_ON Cull statistics including how many nodes and pfGeoSets are being tested how many are accepted and how many are rejected by the libpf culling task enabled with pfFStatsClass pfGetChanFStats chan PFFSTATS_ENDB PFSTATS_ON Fill Statistics The fill statistics display indicates how many millions of pixels have been drawn since the last statistics update For information on setting the length of time between statistics updates see Setting Update Rate on page 442 Collecting and Accessing Statistics in Your Application It also computes the average dep
310. enders the vertices of the geometry as points according to pfHlightPntSize NORMALS Displays the normals of the geometry with lines according to pfHlightNormalLength BBOX_LINES Displays the bounding box of the pfGeoSet as BBOX_FILL outlines and or filled box Combined with PFHL_SKIP_BASE this is a fast highlighting mode SKIP_BASE Causes the normal drawing phase of the pfGeoSet to be skipped This is recommended when using PFHL_FILL or PFHL_BBOX_FILL For a demonstration of the highlighting styles see the sample program usr share Performer pguide srcflibpr C hlcube c Graphics Library Matrix Routines IRIS Performer provides extensions to the standard graphics library matrix manipulation functions These functions are similar to their graphics library counterparts with the exception that they can be placed in IRIS Graphics State Performer display lists Table 10 16 lists and describes the matrix manipulation routines Table 10 16 Matrix Manipulation Routines Routines Action pfScale Concatenate a scaling matrix pfTranslate Concatenate a translation matrix pfRotate Concatenate a rotation matrix pfPushMatrix Push down the matrix stack pfPushIdentMatrix Push the matrix stack and load an identity matrix on top pfPopMatrix Pop the matrix stack pfLoadMatrix Add a matrix to the top of the stack pfMultMatrix Concatenate a matrix Sprite Transformations A sprite is a special transformation used to
311. endulumData pd pfNodeTravFuncs dcs PFTRAV_APP PendulumFunc NULL pfNodeTravData dcs PFTRAV_APP pd int PendulumFunc pfTraverser trav void userData PendulumData pd PendulumData userData pfDCS dcs pfDCS pfGetTravNode trav if pd gt on 157 Chapter 6 Database Traversal Cull Traversal 158 pfMatrix mat double now pfGetFrameTimeStamp float frac dummy pd gt lastAngle now pd gt lastTime 360 0f pd gt frequency if pd gt lastAngle gt 360 0f pd gt lastAngle 360 0f using sinusoidally generated angl pfSinCos pd gt lastAngle amp frac amp dummy frac 0 200 Ussi frac frac 1 0f frac pd gt angleO frac pd gt anglel pfMakeRotMat mat frac pd gt axis 0 pd gt axis 1 pd gt axis 2 pfDCSMat dcs mat pd gt lastTime now return PFTRAV_CONT The cull traversal occurs in the cull phase of the libpf rendering pipeline and is initiated by calling pfFrame A cull traversal is performed for each pfChannel and determines the portion of the scene to be rendered The traversal processes the subgraphs of the scene that are both visible and selected by nodes in the scene graph that control traversal e g pfLOD pfSequence pfSwitch The visibility culling itself is performed by testing bounding volumes in the scene graph against the channel s viewing frustum For customizing the cull traversal libpf provid
312. ene is represented by a graph of nodes libpf provides several specialized node types that encapsulate many graphics and visual simulation features These node types belong to a type hierarchy which is distinct from the database hierarchy described in Chapter 6 The following sections describe the node types Attribute Inheritance The basic element of a scene hierarchy is the node While IRIS Performer supplies many specific types of nodes it also uses a concept called class inheritance which allows different node types to share attributes For example many types of nodes have children but different node types perform different types of operations on their children Only one set of routines is provided for adding and removing children but all the node types can use these routines in the same manner to perform these common operations This reduces the number of routines required and imposes a logical structure on the node types This logical structure is also known as a class hierarchy but it should not be confused with the scene hierarchy of nodes the derivation hierarchy contains data types not objects IRIS Performer s node hierarchy begins with the pfNode class just as the overall class hierarchy begins with the pfObject type see Nodes on page 112 All node types are subordinate to pfNode and they inherit pfNode s attributes and the libpf routines for setting and getting attributes In general a node type inherits the at
313. ent Display Lists pfDispList IRIS Performer supports special libpr display lists They don t use graphics library objects but rather a simple token data mechanism that doesn t cache geometry data These display lists cache only libpr state and rendering commands They also support function callbacks to allow applications to perform special processing during display list rendering Display lists can be reused and are therefore useful for multiprocessing producer consumer situations in which one process generates a display list of the visible scene while another one renders it Note that you can also use OpenGL and IRIS GL display lists in IRIS Performer applications Math Support Extensive linear algebra and simple geometric functions are provided Some supported data types are point segment vector plane matrix cylinder sphere frustum and quaternion Intersections Functions are provided to perform intersections of segments with cylinders spheres boxes planes and geometry Intersection functions for spheres cylinders and frustums are also provided Color Tables pfColortable IRIS Performer supports global color tables that can define the colors used by pfGeoSets Color tables can be used for special effects such as infrared lighting and can be switched in real time 33 Chapter 2 IRIS Performer Basics 34 Asynchronous File I O pfFile A simple nonblocking file access method is provided to allow appl
314. ent 198 Level of Detail Models 199 Level of Detail States 202 Level of Detail Range Processing 204 Level of Detail Transition Blending 207 Terrain Level of Detail 209 Dynamic Load Management 210 Successful Multiprocessing With IRIS Performer 213 Review of Rendering Stages 214 Choosing a Multiprocessing Model 214 Asynchronous Database Processing 220 Rules for Invoking Functions While Multiprocessing 222 Multiprocessing and Memory 226 Shared Memory and pfInit 226 pfDataPools 227 Passthrough Data 228 Creating Visual Effects 231 Using pfEarthSky 231 Atmospheric Effects 232 Light Points 236 pfLightPoint 236 pfLPointState 237 Spotlights and Shadows 242 Morphing 244 Importing Databases 251 Overview of Performer Database Creation and Conversion 251 libpfdu Utilities for Creation of Efficient Performer Run Time structures 252 pfdLoadFile Loading Arbitrary Databases into Performer 252 Database Loading Details 254 Developing Custom Importers 257 Structure and interpretation of the Database File Format 258 Scene Graph Creation using Nodes as defined in libpf 258 Defining Geometry and Graphics State for libpr 258 Creation of a Performer Database Converter using libpfdu 259 Supported Database Formats 269 Description of Supported Formats 271 AutoDesk 3DS Format 271 Silicon Graphics BIN Format 271 Side Effects POLY Format 273 Brigham Young University BYU Format 275 Designer s Workbench DWB Format 276 AutoCAD DXF Format 277 Mul
315. ent casting for you When you use the C API such type casting is not necessary 115 Chapter 5 Nodes and Node Types 116 pfNode Operations In addition to sharing attributes certain basic operations are provided for all node types They include New Create and return a handle to a new node Get Get node attributes Set Set node attributes Find Find a node based on its name Print Print node data Copy Copy node data Delete Delete a node The Set operation is implied in the node attribute name The names of the attribute getting functions contain the string Get An Example of Scene Creation Example 5 1 illustrates the creation of a scene that includes two different kinds of pfNodes For information about pfScene nodes see pfScene Nodes on page 125 for information about pfDCS nodes see pfDCS Nodes on page 126 Example 5 1 Making a Scene pfScene scene pfDCS dcsl dcs2 scene pfNewScene Create a new scene node dcsl pfNewDCS Create a new DCS node dcs2 pfNewDCS Create a new DCS node pfCopy dcs2 dcsl Copy all node attributes from dcsl to dcs2 pfNodeName scene Scene_Graph_Root Name scene node pfNodeName dcs1 DCS_1 Name desl pfNodeName dcs2 DCS_2 Name dcs2 Use a pfGet routine to determine node name printf Name of first DCS node is s pfGetNodeName dcs1 Nodes R
316. entire class enable mask to all PFSTATS_ALL effectively enabling all statistics classes pfFStatsClass fstats PFFSTATS_ALL PFSTATS_SET Force off all modes of the PFSTATS_GFX class of a pfStats pfStatsClassMode stats PFSTATS_GFX PFSTATS_OFF PFSTATS_SET To track triangle strip lengths on a pfFrameStats enable the graphics statistics class mode pfFStatsClassMode fstats PFSTATS_GFX PFSTATS_GFX_TSTRIP_LENGTHS PFSTATS_ON Chapter 13 Performance Tuning and Debugging This chapter explains how to use performance measurement and debugging tools and provides hints for deriving maximum performance from your applications Chapter 13 Performance Tuning and Debugging This chapter provides some basic guidelines to follow when tuning your application for optimal performance It also describes how to use debugging tools like pixie prof gldebug and glprof to debug and tune your applications It concludes with some specific notes on tuning applications on systems with RealityEngine graphics Performance Tuning Overview This section contains some general performance tuning principles Some of these issues are discussed in more detail later in this chapter e Remember that high performance doesn t come by accident You must design your programs with speed in mind for optimal results e Tuning graphical applications particularly IRIS Performer applications requires a pipeline based approac
317. eoe installed If you want to ensure that your customers will have all the libraries they need you should use static linking Debug DSO static optimized and static debug versions of the libraries can be found in optional subsystems and are installed under the directories usr lib Performer Debug usr lib Performer Static and usr lib Performer StaticDebug respectively The L option to cc CC or Id can be used to link with the static libraries Use of Compiling and Linking IRIS Performer Applications the standard DSO or debug DSO is determined at run time through the environment variable LD_LIBRARY_PATH Note See Chapter 9 Importing Databases for information concerning file readers which are normally accessed as DSOs at run time even when the main IRIS Performer libraries have been statically linked Also when linking statically you should not use the no_unresolved option since IRIS Performer may reference symbols such as OpenGL extensions which are not installed on your machine Using Compiler Flags Much of the sample code in this guide many of the sample applications and most of the database importing code are written in ANSI C They should be compiled using the ansi flag to the C compiler Using cckr instead of ansi affects IRIS Performer in the following ways 1 Because cckr doesn t support floating point constants denoted with the f suffix all constants defined with define are double precision The
318. eometry resulting from different primitive types This example uses index lists that index the coordinate array Note that the flat shaded line strip and flat shaded triangle strip 323 Chapter 10 libpr Basics primitives have the vertices listed in the same order as for the smooth shaded varieties Vertex list Xa Ya ZA Xp YB ZB Xc Yo 2c Xp YD ZD n XN YN ZN Geometry Q 0 1 Index list 2 3 Primitive Independent iiangles Quadrilaterals Triangle strips 0 1 2 Index list 3 Figure 10 1 Primitives and Connectivity 324 Geometry Attributes The definition of a primitive isn t complete without attributes In addition to a primitive type and count a pfGeoSet references four attribute arrays see Figure 10 2 e colors red green blue alpha e normals Nx Ny Nz e texture coordinates S T e vertex coordinates X Y Z A pfGeoState is also associated with each pfGeoSet see Graphics State on page 333 and Figure 10 3 for details The four components listed above can be specified with pfGSetAttr and in two ways by indexed specification using a pointer to an array of components and a pointer to an array of indices or by direct specification providing a NULL pointer for the
319. epresentations and build sorted optimized display list for the draw stage Draw Issue graphics library commands to a Geometry Pipeline in order to create an image for subsequent display You can partition these stages into separate parallel processes in order to distribute the work among multiple CPUs Depending on your system type and configuration you can use any of several available multiprocessing models Choosing a Multiprocessing Model Use pfMultiprocess to specify which functional stages if any should be forked into separate processes The multiprocessing mode is actually a bitmask where each bit indicates that a particular stage should be configured as a separate process For example the bit PFMP_FORK_DRAW means the Successful Multiprocessing With IRIS Performer draw stage should be split into its own process Table 7 3 lists some convenience tokens that represent common multiprocessing modes Table 7 3 Multiprocessing Models Model Name Description PFMP_APPCULLDRAW PFMP_APP_CULLDRAW or PFMP_FORK_ CULL PFMP_APPCULL_DRAW or PFMP_FORK_ DRAW PFMP_APP_CULL_DRAW or PFMP_FORK_CULL PFMP_FORK_ DRAW Combine the application cull and draw stages into a single process In this model all of the stages execute within a single frame period This is the minimum latency mode of operation Combine the cull and draw stages in a process that is separate from the application process This model provide
320. er material changes do tend to be expensive Sharing materials among different objects can be increased with the use of pf MtlColorMode that is PFMTL_CMODE_AD by default However on some older graphics platforms such as the Elan Extreme and VGX the use of pfMtlColorMode which actually calls the IRIS GL function Imcolor or the OpenGL function glColorMaterial has some associated per vertex cost and should be used with some caution If you cull stage is not a bottleneck make sure your pfChannels sort the scene by graphics state Even if you are running in single process mode the extra time taken to sort the database is often more than offset by the savings in rendering time See Sorting the Scene in Chapter 6 for more details on how to configure sorting Fill Bottlenecks Here are some methods of dealing with fill stage bottlenecks One technique to hide the cost of expensive fill operations is to fill the pipeline from the back forward so that no part is sitting idle waiting for an upstream stage to finish The last stage of the pipeline is the fill stage so by drawing backgrounds or clearing the screen via pfClearChan first before pfDraw you can keep the fill stage busy In addition if you have a couple of large objects that reliably occlude much of the scene drawing them very early on can both fill up the back end stage and also reduce future fill work because the occluded parts of the scene will fail a z buffer
321. er of children and each child has its own duration You can control whether an entire sequence repeats from start to end repeats from end to start or terminates Use pfNewSeq to create and return a handle to a new pfSequence Once the pfSequence has been created use the group function pfAddChild to add the children that you want to animate Table 5 4 describes the functions for working with pfSequences Table 5 4 pfSequence Functions Function Description pfNewSeq Create a new pfSequence node pfSeqTime Set the length of time to display a frame pfGetSeqTime Find out the time allotted for a given frame pfSeqInterval Set the range of frames and sequence type pfGetSeqInterval Find out interval parameters pfSeqDuration Control the speed and number of repetitions of the entire sequence pfGetSeqDuration Retrieve speed and repetition information for the sequence pfSeqMode Start stop pause and resume the sequence pfGetSeqMode Find out the sequence s current mode pfGetSeqFrame Get the current frame Example 5 5 demonstrates a possible use of both switches and sequences First sequences are set up to contain animation sequences for explosions fire and smoke then a switch is used to control which sequences are currently active Node Types Example 5 5 Using pfSwitch and pfSequence Nodes pfSwitch s pfSequence explosionl_seq explosion2_seq fire_seq or smoke_seq pfNewSwitch ex
322. er 474 Legal Creation of Objects in C 486 Illegal Creation of Objects in C 487 Class Definition for a Subclass of pfDCS 491 Overloading the libpf Application Traversal 492 Changeable Static Data Member 495 xvii Figures Figure 1 1 Figure 2 1 Figure 2 2 Figure 2 3 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 Figure 4 5 Figure 5 1 Figure 5 2 Figure 5 3 Figure 6 1 Figure 6 2 Figure 6 3 Figure 6 4 Figure 7 1 Figure 7 2 Figure 7 3 Figure 7 4 Figure 7 5 Figure 8 1 Figure 9 1 Figure 9 2 Figure 9 3 Figure 9 4 A Section of the New Jerusalem City Hall 4 IRIS Performer Library Hierarchy 15 Relationship of IRIS Performer to Database Formats 39 Partial Inheritance Graph of IRIS Performer DataTypes 44 Single Graphics Pipeline 74 Dual Graphics Pipeline 75 Symmetric Viewing Frustum 94 Heading Pitch and Roll Angles 96 Single Channel and Multiple Channel Display 101 Nodes in the IRIS Performer Hierarchy 113 Shared Instances 121 Cloned Instancing 122 Culling to the Frustum 161 Sample Database Objects and Bounding Volumes 163 How to Partition a Database for Maximum Efficiency 165 Intersection Methods 187 Frame Rate and Phase Control 194 Level of Detail Node Structure 200 Level of Detail Processing 201 Stress Processing 211 Multiprocessing Models 219 Layered Atmosphere Model 233 BIN Format Data Objects 272 Soma Cube Puzzle in DWB Form 277 The Famous Teapot in DXF Form 278 Spacecraft Model in FLIGHT
323. eres that contain bound the geometry in their descendent nodes The purpose of bounding volumes is to allow a quick test of a region for being off screen or out of range of intersection search vectors buffer scope All IRIS Performer nodes are created in a pfBuffer either the primary application buffer or in an alternate returned by pfNewBuffer Only one pfBuffer is considered current and this buffer can be selected using pfSelectBuffer All new nodes are created in the current pfBuffer and will be visible only in the current buffer until that pfBuffer is merged into the application buffer using pfMergeBuffer A process cannot access nodes that do not have scope in its current buffer except through the special buffer commands pfBufferAddChild pfBufferRemoveChild and pfBufferClone Thus they are said to have buffer scope channel A visual channel specifies how a geometric scene should be rendered to the display device This includes the viewport area on the screen as well as the location orientation and field of view associated with the viewer or camera channel group A set of channels that share attributes such as the eyepoint or callbacks When a shared attribute is set on any member of the group all members get the new value Channel groups are most commonly used for adjacent displays making up a panorama channel share mask A bit mask indicating the attributes that are shared by all channels ina channe
324. erformed in the following order 1 Prune the node based on the bitwise AND of the traversal masks of the node and the pfChannel or pfSegSet If pruned traversal continues with the nodes siblings 2 invoke the node s pre traversal callback if any and either prune continue or terminate the traversal depending on callback s return value 3 Traverse beginning again at step 1 the node s children or geometry pfGeoSets If the node is a pfSwitch a pfSequence or a pfLOD the state of the node affects which children are traversed 4 Invoke the node s post traversal callback if any 155 Chapter 6 Database Traversal 156 State Inheritance In addition to imposing a logical and spatial ordering of the database the hierarchy also defines how state is inherited between parent and child nodes during scene graph traversals For example a parent node that represents a transformation causes the subsequent transformation of each of its children when it and they are traversed In other words the children inherit state which includes the current coordinate transformation from their parent node during database traversal A transformation is a 4x4 homogeneous matrix that defines a 3D transformation of geometry which typically consist of scaling rotation and translation The node types pfSCS and pfDCS both represent transformations Transformations are inherited through the scene graph with each new transformation bei
325. errain each representing the whole surface but with exponentially fewer numbers of polygons in each version The numbers of highest LOD tiles that will tessellate the entire terrain surface in the X and Y axis directions Two numeric values that define the mapping of texture image pixels to world coordinate terrain geometry These values are the number of meters per texel texture pixel of filtered grid post data in the X and Y axis dimensions The name of an image file that represents terrain height at regularly spaced sample points in the form of a monochrome image whose brightness at each pixel indicates the height at that sample point Additional arguments are the number of samples in the input image in the X and Y directions as well as the desired number of samples in these directions The pfdLoadFile_ptu function resamples the grid posts from the original to the desired resolution by filtering the height image using SGI ImageVision Library functions The name of an image file that represents the terrain texture image at regularly spaced sample points Subsequent arguments are the number of samples in the image in the X and Y directions as well as the desired number of samples in these directions This image will be applied to the terrain geometry The scale values provided in the PTU file allow the terrain grid and texture image to be adjusted to create an orthographic alignment An optional second texture image filename that serves
326. es Such utilities often prove very useful most modeling tools and file formats represent their data in structures that correspond to the way users model data but such data structures are often mutually exclusive with effective and efficient IRIS Performer run time structures libpfdu contains many utilities including DSO support for database loaders and their modes file path support and so on but the heart of libpfdu is the notion of the IRIS Performer database builder The builder is a tool that allows users to input or output a collection of geometry and graphics state in immediate mode Users send geometric primitives one at a time each with its corresponding graphics state to the builder When the builder has received all the data the user simply requests optimized IRIS Performer data structures which can then be used as a part of a scene graph The builder hashes geometry into different bins based on the geometry s attribute binding types and associated graphics state It also keeps track of graphics state elements textures materials light models fog and so on and shares state elements whenever possible Finally the builder creates pfGeoSets that contain triangle meshes created by running the original geometry through the libpfdu triangle meshing utility To go along with each pfGeoSet the builder creates a pfGeoState IRIS Performer s encapsulated state primitive which has been optimized to share as many attribu
327. es must happen here DrawFunc pfChannel chan void data PreDraw chan data Clear the viewport etc pfDraw Render the frame draw HUD read IRIS GL devices or whatever else needs to be done post draw PostDraw chan data 99 Chapter 4 Setting Up the Display Environment 100 Using Multiple Channels Each rendering pipeline can render multiple channels to multiple windows Each channel represents an independent viewpoint into either a shared or an independent visual database Different types of application can have vastly different pipeline window channel configurations This section describes two basic extremes visual simulation applications where there is typically one window per pipeline and highly interactive uses that require dynamic window and channel configuration One Window per Pipe Multiple channels per Window Often there will is a single channel associated with each pipeline as shown in the top half of Figure 4 5 This section describes two important uses for multiple channel support multiple pipelines per system and multiple windows per pipeline the second of which is illustrated in the bottom half of Figure 4 5 Using Channels Single Channel Frame Buffer Display Device Channel 0 Multiple Channel Frame Buffer Channel 0 Channel 1 Channel n 1 Display Device Figure 4 5 Single Channel and Multiple Channel Display 101 C
328. es of each task with minimal overhead and you don t need to display the timing graph However for most applications the overhead incurred by keeping the timing history is not noticeable Controlling Update Rate The update rate controls how often statistics are averaged and new results are made available in the AVG buffer for display or query Change the update rate by calling pfFStatsAttr fstats PFFSTATS_UPDATE_FRAMES PFFSTATS_UPDATE_SECS val When the update rate is nonzero statistics are accumulated every frame When the update period is set to zero no statistics accumulation or averaging is done and only statistics in the PREV and CUR buffers are maintained When statistics are accumulated and averaged the averaging happens only in the application process but accumulation is done in each IRIS Performer process Statistics Output Once you ve collected some statistics you need to be able to access and manipulate them Printing To print the contents of pfStats and pfFrameStats structures use the general pfPrint routine The verbosity level parameter to pfPrint sets the level of detail to use in printing statistics Statistics class enable bitmasks can be used to select a subset of statistics to print For instance to print only the enabled statistics pfPrint stats pfGetStatsClass stats PFSTATS_ALL PFPRINT_VB_INFO 0 When printing the contents of pfFrameStats structures y
329. es read or write the same chunk of data at the same time consequences can be dire For example one process might read the data while in an inconsistent state and end up dumping core while dereferencing a NULL pointer e Memory synchronization IRIS Performer is configured as a pipeline where different processes are working on different frames at the same time This pipelined nature is illustrated in Figure 7 5 which shows that for instance in the PFMP_APP_CULL_DRAW configuration the application process is working on frame n while the draw process is working on frame n 2 If in this case if we have only a single memory location representing the viewpoint then it is possible for the application to set the viewpoint to that of frame n and the draw process to incorrectly use that same viewpoint for frame n 2 Properly synchronized data is called frame accurate Fortunately IRIS Performer transparently solves all of the above problems for most IRIS Performer data structures and also provides powerful tools and mechanisms that the application can use to manage its own memory Shared Memory and pflnit As described in Initializing and Configuring IRIS Performer in Chapter 3 pfInit creates a shared memory arena that is shared by all processes spawned by IRIS Performer and all user processes that are spawned from any IRIS Performer process A handle to this arena is returned by pfGetSharedArena and should be used as the arena argument
330. es traversal masks and function callbacks for each node in the database as well as a function callback in which the application can do its own culling of custom data structures Cull Traversal Traversal Order The cull is a depth first traversal of the database hierarchy beginning at a pfScene which is the hierarchy s root node For each node a series of tests is made to determine whether the traversal should prune the node that is eliminate it from further consideration or continue on to that node s children The cull traversal processing is much as described earlier in particular the draw traversal masks are compared and the node is checked for visibility before the traversal continues on to the nodes children 1 Prune the node based on the channel s draw traversal mask and the node s draw mask 2 Invoke the node s pre cull callback and either prune continue or terminate the traversal depending on callback s return value 3 Prune the node if its bounding volume is completely outside the viewing frustum 4 Traverse beginning again at step 1 the node s children or geometry pfGeoSets if the node is completely or partially in the viewing frustum If the node is a pfSwitch a pfSequence or a pfLOD the state of the node affects which children are traversed 5 Invoke the node s post cull callback The following sections discuss these steps in more detail Visibility Culling Culling determines
331. escription Default Value PFSTATE_ENTEXTURE Texturing enable flag PF_OFF PFSTATE_ENFOG Fogging enable flag PF_OFF PFSTATE_ENWIREFRAME pfGeoSet wireframe PF_OFF mode enable flag PFSTATE_ENCOLORTABLE pfGeoSet colortable PF_OFF enable flag PFSTATE_ENHIGHLIGHTIN pfGeoSet highlighting PF_OFF G enable flag PFSTATE_ENLPOINTSTATE pfGeoSet light point PF_OFF state enable flag PFSTATE_ENTEXGEN Texture coordinate PF_OFF generation enable flag The mode control functions described in the following sections should be used in place of their graphics library counterparts so that IRIS Performer can correctly track the graphics state Use pfGStateMode with the appropriate PFSTATE token to set the mode of a pfGeoState Transparency You can control transparency using pfTransparency Possible transparency modes are Table 10 7 pfIransparency Tokens Transparency mode Description PFTR_OFF Transparency disabled PFTR_ON Use the fastest but not necessarily the PFTR_FAST best transparency provided by the hardware PFTR_HIGH_QUALITY Use the best but not necessarily the fastest transparency provided by the hardware Graphics State Table 10 7 continued pfIransparency Tokens Transparency mode Description PFTR_MS_ALPHA Use screen door transparency when multisampling Fast but limited number of transparency levels PFTR_BLEND_ALPHA Use alpha based blend with background color Slower but high number of
332. esigned to run at a fixed frame rate specified by the application IRIS Performer measures graphics load and uses that information to compute a stress value Stress is applied to the model s level of detail to reduce scene complexity when nearing graphics overload conditions IRIS Performer also provides frame synchronization between pfChannels and the Geometry Pipeline hardware to ensure that displays are updated in lockstep 31 Chapter 2 IRIS Performer Basics 32 Special Features pfEarthSky pfSequence pfLightPoint libpf provides an environmental model called a pfEarthSky consisting of ground and sky polygons that efficiently clears the viewport before rendering the scene Atmospheric effects such as ground fog haze and clouds are included Sequenced animations using pfSequence nodes allow the application to efficiently render complex geometry sequences that aren t easily modeled otherwise You can think of animation sequences as a series of flip cards where the application controls which card is shown and for how long Light points defined by pfLightPoint nodes can be used to simulate runway lights approach lights strobes beacons and street lights The parameters for a pfLightPoint include size directionality shape color and intensity IRIS Performer renders light points using modes appropriate to the hardware Enhanced support for light point simulation is provided by the IRIS Performer pfLPoin
333. ethod is the displace decaling method In this case each layer is displaced towards the eye so it hovers slightly above the preceding layer Displaced decals need not be coplanar can be drawn in any order but the displacement may cause geometry to incorrectly poke through other geometry Decals consist of base geometry and layer geometry The base defines the depth values of the decal while layer geometry is simply inlaid on top of the base Multiple layers are supported but limited to 8 when using displaced decals Realize that these layers imply superposition there is no limit to the number of polygons in a layer only to the number of distinct layers The decal mode indicates whether the subsequent geometry is base or layer and the decal method to use For example a mode of PFDECAL_BASE_STENCIL means that subsequent geometry is to be considered as base geometry and drawn using the stencil method All combinations of base layer and displace stencil modes are supported but you should make sure to use the same method for a given base layer pair Graphics State Example 10 3 illustrates the use of pfDecal Example 10 3 Using pfDecal to draw road with stripes pfDecal PFDECAL_BASE_STENCIL draw underlying geometry roadway here pfDecal PFDECAL_LAYER_STENCIL draw coplanar layer geometry stripes here pfDecal PFDECAL_OFF Note libpf app
334. f IRIS Performer s pre order visitations of a hierarchical scene graph Traversals for application culling and intersection processing are internal to libpf and user written traversals are supported by the pfuTraverser tools traversing See traversals trigger routine A routine that initiates a traversal or the invocation of a callback in another process pfCull triggers the cull traversal pfFrame triggers processing for the current frame up vector The Z axis of the eyepoint defining the display s up direction Must be perpendicular to the gaze vector view volume visualization The display of the viewing frustum for a particular channel usually done by rendering a wireframe version of the frustum with a different eye point or field of view See cull volume visualization viewing frustum The frustum containing the portion of the scene database visible from the current eyepoint viewpoint The location of the camera or eye used to render the scene 529 Glossary 530 viewport The portion of the framebuffer used for rendering Each pfChannel has a viewport in the framebuffer of its corresponding pfPipeWindow visual An construct that the X Window System uses to identify framebuffer configurations widget A manipulable or decorative element of a graphical user interface Much of the programming for GUI elements is associated with defining the reaction of widgets to user mouse and keyboard
335. f objects 50 type system multiprocessing implications 494 typographical conventions xxviii U UNC format See formats unidirectional lights 237 unidirectional lights See also lighting University of Minnesota Geometry Center 314 University of North Carolina 314 updatable objects 495 update rate 63 updates latency critical 457 up vector defined 529 user data 45 user interfaces 41 562 using te builder 36 usinit 355 usnewlock 227 387 388 usnewsema 387 388 ussetlock 227 usunsetlock 227 V van Dam Andries xxix van der Rohe Ludwig Mies 283 VClock See video counter vector routines 397 vectors 2 component 397 3 component 397 4 component 397 vehicly simulation xxxii video counter 34 385 video field 427 video retrace period 63 video scan rate 194 video splitting 103 view matrix 97 offset 97 viewing angles 95 viewing frustum definition 529 intersection with 162 viewing offsets 97 viewing parameters 93 95 viewpoint 95 definition 529 viewports 93 defined 530 views inset 102 view volume visualization definition 529 virtual addresses and multiprocessing 494 virtual functions address space issues 494 virtual reality xxv 13 16 virtual reality markup language 157 See also VRML 157 virtual set xxv visibility culling 159 163 visual defined 530 visual latency 21 visual priority See coplanar geometry visual programming 16
336. fMorphAttr morph 1 3 nSph NULL ER_VERTEX icoords 2 srcs NULL NULL pfGSetAttr gset PFGS_NORMAL3 PFGS_PER_VERTEX void pfGetMorphDst morph 1 return morph inorms Chapter 9 4 Importing Databases This chapter describes a variety of database formats and their corresponding conversion utilities Chapter 9 Importing Databases Overview of Performer Database Creation and Conversion Once you ve learned how to create visual simulation applications with IRIS Performer your next task is to import visual databases into those applications Import and export functions for more than 30 popular database formats are provided with IRIS Performer to ease this effort This chapter describes the steps involved in creating custom loaders for other data formats and then reviews each of these pre existing file loading utilities Along the way it also describes several utility functions in the IRIS Performer database utility library that can make the process of database conversion easier for you Source code is provided for most of the tools discussed in this chapter In most cases the loaders are short easy to understand and easy to modify Table 9 1 lists the subdirectories of usr share Performer src lib where you can find the source code for the database processing tools Table 9 1 Database Importer Source Directories Directory Name Directory Contents libpfdu General
337. fNodeBSphere geode NULL PFBOUND_STATIC pfGetGSetAttrLists gset PFGS_COORD3 void amp coords amp icoords pfGetGSetAttrLists gset PFGS_NORMAL3 void amp norms amp inorms nSph pfGetSize coords sizeof pfVec3 246 Morphing ncoords pfMalloc pfGetSize coords arena nnorms pfMalloc pfGetSize norms arena for i 0 i lt nSph i int max float C Find which face of the cube this vertex maps to if PF_ABS coords i PF_X gt PF_ABS coords i PF_Y if PF_ABS coords i PF_X gt PF_ABS coords i PF_Z max PF_X else max PF_Z else if PF_ABS coords i PF_Y gt PF_ABS coords i PF_Z max PF_Y else max PF_Z Compute cube normals and coordinates pfSetVec3 nnorms i 0 0f 0 0f 0 0f if coords i max lt 0 0f t 1 0f coords i max pfScaleVec3 ncoords i t coords i nnorms i max 1 0f else t 1 0 coords i max pfScaleVec3 ncoords i t coords i nnorms i max 1 0f Morph attribute 0 is coordinates srces 0 float coords srces l1 float ncoords pfMorphAttr morph 0 3 nSph NULL 2 srcs NULL NULL 247 Chapter 8 Creating Visual Effects 248 pfGSetAttr gset PFGS_COORD3 PFGS_P void pfGetMorphDst morph 0 Morph attribute 1 is normals srces 0 float norms srces l1 float nnorms p
338. fSphereAroundSpheres Sphere around a set of spheres Bounding volumes can also be defined by extending existing volumes but in many cases the tightness of the bounds created through a series of extend operations is substantially inferior to that of the bounds created with a single pf Around operation Table 11 6 lists and describes the routines for extending bounding volumes Table 11 6 Routines to Extend Bounding Volumes Routine Operation pfBoxExtendByPt Extend a box to enclose a point pfBoxExtendByBox Extend a box to enclose another box pfSphereExtendByPt Extend a sphere to enclose a point pfSphereExtendBySphere Extend a sphere to enclose a sphere Creating and Transforming Volumes Transforming Bounding Volumes Transforming the volumes with an orthonormal transformation that is with no skew or nonuniform scaling is straightforward for all of the volumes except for the axially aligned box A straight transformation of the vertices doesn t suffice because the new box would no longer be axially aligned so an aligned box must be created that encloses the transformed vertices Hence a transformation of a box isn t generally reversed by applying the inverse transformation to the new box Table 11 7 lists and describes the routines that transform bounding volumes Table 11 7 Routines to Transform Bounding Volumes Routine Operation pfOrthoXformPlane Transform a plane or half space pfOrthoXformFrust Tran
339. ficient than a spatial organization which arranges geometry by location A spatial organization improves culling and intersection performance in the example of the town spatial organization would consist of grouping houses with their local terrain geometry instead of with each other Chapter 6 describes how to spatially organize your database for best performance The code fragment in Example 5 2 illustrates building a hierarchy using pfGroup nodes Example 5 2 Hierarchy Construction Using Group Nodes scene pfNewScene The following loop constructs a sample hierarchy by adding children to several different types of group nodes Notice that in this case the terrain was broken up spatially into a 4x4 grid and a switch node is used to cause only one vehicle per terrain node to be traversed FF F F F for j 0 j lt 4 Jtt for i 0 i lt 4 i fFGroup spatial_terrain_block pfNewGroup FSCS house_offset pfNewSCs FSCS terrain_block_offset pfNewSCS FDCS car_position pfNewDCS FDCS tank_position pfNewDCS FDCS heli_position pfNewDCS FSwitch current_vehicle_type fFGeode heli car tank a oO 0 O TO OU D e fAddChild scene spatial_terrain_block pfAddChild spatial_terrain_block terrain_block_offset pfAddChild spatial_terrain_block house_offset pfAddChild spatial_terrain_block current_vehicle_type pfAddChild current_vehicle_type car_posi
340. flickering fire 244 Morphing e texture coordinates to simulate rippling ocean waves e coordinates to make a 3D model of a face smile or frown pfMorph is a group node that supports the morphing of lists of numbers These numbers could be colors coordinates or pixels it is up to you to decide what to morph Conceptually pfMorph combines multiple input lists of numbers into a single output list This output may be used arbitrarily but is most often used as a pfGeoSet attribute array be it colors normals texture coordinates or coordinates The combination is linear that is the input lists are scaled by a value which has no restricted range and then summed together to produce the output One example of geometric morphing is in facial animation where multiple input faces with canonical expressions smiley frowny surprised are combined to produce a face with a mixture of expressions pfMorphs can handle multiple sets of input gt output lists so a single pfMorph could for example morph the normals and coordinates of an animated figure An input gt output set is called a morph attribute since a set typically corresponds to a pfGeoSet attribute Morph attributes are specified with pfMorphAttr Example 8 4 is a snippet of the morph c test program in usr share Performer src pguide libpf C shows how to configure a pf Morph node that morphs the normals and coordinates of a pfGeoSet Example 8 4 How to set up a pfMorph node
341. for achieving the fade LOD effect It s a common misperception that screen door transparency on RealityEngine gives you n levels of transparency for n multisamples In fact n samples gives you 4n levels of transparency because RealityEngine uses 2 pixel by 2 pixel dithering However screen door transparency causes a dramatic increase in the number of complex pixels in a scene which can affect fill performance Texturing Texturing is free on a RealityEngine if you use a 16 bit texel internal texture format There are 16 bit texel formats for each number of components These formats are used by default by IRIS Performer but can be set on a pfTexture with pfTexFormat Using a 32 bit texel format will yield half the fill rate of the 16 bit texel formats Do not use huge ranges of texture coordinates on individual triangles This can incur both an image quality degradation and a severe performance degradation Keep the maximum texture coordinate range for a given component on a single triangle under 1 lt lt 13 logs TexCSize where TexCSize is the size in the dimension of that component The use of Detail Texture and Sharpen can greatly improve image quality Minimize the number of different detail and sharpen splines or just use the internal default splines Applying the same detail texture to many base textures can incur a noticeable cost when base textures are changed Detail textures are intended to be derived from a high resolution
342. for g1 123 Chapter 5 Nodes and Node Types 124 Example 5 4 Automatically Updating a Bounding Volume pfAddchild gl dcs pfAddChild dcs helicopter pfDCSRot dcs heading 10 0f pitch roll pfDCSRot dcs heading pitch 5 0f roll 2 0f In some cases you may not want bounding volumes to be recomputed automatically For example in a merry go round with horses moving up and down you know that the horses stay within a certain volume Using pfNodeBSphere you can specify a bounding sphere within which the horse always remains and tell IRIS Performer that the bounding volume is static not to be updated no matter what happens to the node s children You can always force an update by setting the bounding volume to NULL with pfNodeBSphere as follows pfNodeBSphere node NULL NULL PFBOUND_STATIC At the lowest level within pfGeoSets bounding volumes are maintained as axially aligned boxes When you add a pfGeoSet to a pfGeode or directly invoke pfGetGSetBBox on the pfGeoSet a bounding box is created for the pfGeoSet Neither the bounding box of the pfGeoSet nor the bounding volume of the pfGeode is updated if the geometry changes inside the pfGeoSet You can force an update by setting the pfGeoSet bounding box and then the pfGeode bounding volume to a NULL bounding box as follows e Recompute the pfGeoSet bounding box from the internal geometry pfGSetBBox gset NULL e Recompute the pfGeode bou
343. forcing 216 functions invoking during 222 225 initializing 62 memory management 226 228 models of 214 219 cull overlap draw 216 timing diagrams 218 order of calls 218 pipelines 174 pipelines multiple 217 544 uses for 213 multisampling 24 476 multithreading 217 defined 521 mutual exclusion definition 522 N Nagaoka Isao 504 naming conventions for IRIS Performer 35 NaN Not a Number exception 475 Neider Jackie xxx Newman William M xxix NFF format See formats node draw mask 170 nodes callbacks 171 defined 522 overview 30 31 pruning 159 sequences 128 nonblocking access definition 522 nonblocking file interface 391 non degrading priorities definition 522 notification levels for errors 391 Nye Adrian xxxi 0 O Reilly Tim xxxi object derivation 42 object type 50 OBJ format See formats occlusion culling definition 522 ogldebug 467 468 469 ogldebug utility 468 Onyx RealityEngine2 xxv Onyx RealityEngine See RealityEngine graphics open 391 OpenGL xxv documentation xxx functions glAlphaFunc 337 glBlendFunc 476 glColorMaterial 449 455 478 glFinish 434 glFog 350 glLight 348 glMaterial 349 glPointSize 236 glShadeModel 454 glStencilOp 338 glTexEnv 342 glTexGen 347 glTexImage2D 342 343 glTexSubImage 345 glXCreateContext 371 library and application suffix 40 overview 40 41 portin
344. form Bottlenecks A transform bottleneck can arise from expensive vertex operations from a scene that s typically drawn with many very tiny polygons from a scene modeled with inefficient primitive types or from excessive mode or transform operations Here are some tips on reducing such bottlenecks 454 Connected primitives will have better vertex rates than independent primitives and quadrilaterals are typically much more efficient in vertex operations than independent triangles are The expensive vertex operations are generally lighting calculations The fastest lighting configuration is always one infinite light Multiple lights local viewing models and local lights have in that order dramatically increasing cost Two sided lighting also incurs some additional transform cost On some graphics platforms texturing and fog can add further significant cost to per vertex transformation The channel graphics statistics will tell you what kinds of lights and light models are being used in the scene Matrix transforms are also fairly expensive and definitely more costly than one or two explicit scale translate or rotate operations When possible flatten matrix operations into the database with pfFlatten The most frequent causes of mode changes are shademodel or glShadeModel textures and object materials The speed of these Specific Guidelines for Optimizing Performance changes depends on the graphics hardware howev
345. fstats In this case it s an error to select more than one statistics buffer so PFSTATS_ALL cannot be used as the select If you specify two pfFrameStats structures the buffer select is used for both structures if you select multiple buffers then each selected statistics class from each selected buffer is copied The pfCopyFStats routine allows you to copy between two different buffers of two pfFrameStats structures This routine takes explicit specification of PFFSTATS_BUF_ selects for source and destination Any PFFSTATS_BUF_ included with the class enable bitmask is simply ignored making it safe to specify PFSTATS_ALL This routine will not accept a pfStats structure 441 Chapter 12 Statistics 442 Querying pfQueryStats and pfMQueryStats and corresponding pfFrameStats versions can be used to get values of out a pfStats or pfFrameStats structure and into an exposed structure These routines are useful when you want to use specific statistics for your own custom load management or for benchmarking and you can use them to implement your own custom statistics utility routines pfQueryStats and pfMQueryStats both take a pfStats or pfFrameStats for pfQueryFStats and pfMQueryFStats and return the number of bytes written to the provided destination buffer pfQueryStats takes a token that specifies a single query while pfMQueryStats expects a token buffer for multiple queries If an error is encountered b
346. fuLockDownDraw These facilities require that the application runs with root permissions The source code for these utilities is in usr share Performer src lib libpfutilfockcpu c For an example of there use see the sample source code in usr share Performer src pguide libpt C bench c For more information about priority scheduling and real time programming see the chapter of the IRIX System Programming Guide entitled Using Real Time Programming Features and the IRX REACT technical report Make sure you aren t generating any floating point exceptions Floating point exceptions can cause an individual computation to incur tens of times its normal cost Furthermore a single floating point exception can lead to many further exceptions in computations that use the exceptional result and can even propagate performance degradation down the process pipeline IRIS Performer will detect and tell you about the existence of floating point exceptions if your 457 Chapter 13 Performance Tuning and Debugging 458 pfNotifyLevel is set to PFNFY_INFO or PFNFY_DEBUG You can then run your application in dbx and your application will stop when it encounters an exception enabling you to trace the cause Minimize the amount of channel data allocated by pfAllocChanData and call pfPassChanData only when necessary to reduce the overhead of copying the data Copying pointers instead of data is often sufficient Cull Process Tips He
347. g Statistics in Your Application If you just want to bring up a statistics display in your application you may not need to know details about the data structures used for statistics If however you want to do more complicated statistics handling including collecting statistics without displaying them you need more advanced information This section provides a general overview of statistics manipulation followed by subsections containing specific information 433 Chapter 12 Statistics 434 If you use libpf a wide variety of statistics manipulation functions is available If you use libpr however you must do some things on your own For instance you have to bind your own pfStats structure in which to accumulate statistics Furthermore you can t access some kinds of statistics except through libpf calls for instance you can t get culling statistics using libpr calls If you want full access to statistics you must use libpf There are however libpr routines that allow you to do your own cumulative totaling and averaging of collected statistics To create your own statistics display enable the statistics classes you want to use and disable any modes you don t want to use Then enable any relevant hardware if necessary with pfEnableStatsHw To ensure the accuracy of timing with your rendering statistics you want to flush the graphics pipeline before calling pfGetTime You can do this in IRIS GL with finish
348. g data The code fragment in Example 6 4 is an example of cull and draw callbacks and the passthrough data that is used to communicate with them Example 6 4 Using Passthrough Data to Communicate With Callback Routines typedef struct long val PassData 177 Chapter 6 Database Traversal 178 void cullFunc pfChannel chan void data j void drawFunc pfChannel chan void data int main PassData pd allocate passthrough data pd PassData pfAllocChanData chan sizeof PassData initialize channel callbacks pfChanTravFunc chan PFTRAV_CULL cullFunc pfChanTravFunc chan PFTRAV_DRAW drawFunc main simulation loop while 1 pfSync pd gt val 0 pfPassChanData chan pfFrame void cullFunc pfChannel chan void data PassData pd PassData data pd gt val t pfCull void drawFunc pfChannel chan void data PassData pd PassData data fprintf stderr Sld n pd gt val pfClearChan chan pfDraw This example would regardless of the multiprocessing mode have the values 0 1 and 1 for pd gt val at the points where pfFrame pfCull and Intersection Traversal Intersection Traversal pfDraw are called In this way control data can be sent down the pipeline from the application through the cull and on to the draw process with frame synchronization without regard to the active multiprocessin
349. g mode When configured as a process separate from the draw the cull callback should not attempt to send graphics commands to an IRIS Performer window because only the draw process is attached to the window Callbacks should not modify the IRIS Performer database but they can use pfGet routines to inquire about database information The draw callback should not call swapbuffers or an equivalent function when using OpenGL because IRIS Performer must control buffer swapping in order to manage the necessary frame and channel synchronization However if you need special control over buffer swapping use pfPipeSwapFunc to register a function as the given pipe s buffer swapping function Once your function is registered it will be called instead of swapbuffers and may then invoke either of these functions You can make spatial inquiries in IRIS Performer by testing the intersection of line segments with geometry in the database For example a single line segment pointing straight down from the eyepoint can determine your height above terrain four such segments can simulate the four tires of a car and segments swept out by points on a moving object can determine collisions with other objects Testing Line Segment Intersections The testing of each line segment or group of spatially grouped segments requires a traversal of part or all of a scene graph You make these inquiries using pfNodelsectSegs which intersects the specified grou
350. g of the scene graph in preparation for rendering a frame It is initiated by calling pfAppFrame If pfAppFrame is not explicitly called the traversal is automatically invoked by pfSync or pfFrame An application traversal can be invoked for each channel but usually channels share the same application traversal see pfChanShare The application traversal updates dynamic elements in the scene graph such as geometric morphing carried invoked by a pfMorph node The application traversal is also often used for implementing animations or other custom processing when it is desirable to have those behaviors embedded in the scene graph and invoked by IRIS Performer rather than requiring application code to invoke them every frame The traversal proceeds as described in Database Traversals The selection of which children to traverse is also affected by the application traversal mode of the channel in particular the choice of all none or one of the children of pfLOD pfSequence and pfSwitch nodes is possible By default the traversal obeys the current selection dictated by these nodes The following example from the Open Inventor loader this loader reads both Open Inventor and VRML files shows a simple callback changing the transformation on a pfDCS every frame This and other examples can be found in usr share Performer src lib libpfiv pfiv C Example 6 1 Application Callback to Make a Pendulum int AttachPendulum pfDCS dcs P
351. g pipeline Then at well defined points in time the passthrough data is copied from its buffer into the next buffer along the pipeline This copying guarantees memory exclusion but you should minimize the amount of passthrough data to reduce the time spent copying Allocate a passthrough data buffer for the rendering pipeline using pfAllocChanData for data to be passed down the intersection pipeline call pfAllocIsectData Data returned from pfAllocChanData is passed to the channel cull and draw callbacks that are set by pfChanTravFunc Data returned from pfAllocIsectData is passed to the intersection callback specified by pfIsectFunc Passthrough data isn t automatically passed through the processing pipeline You must first call pfPassChanData or pfPassIsectData to indicate that the data should be copied downstream This requirement allows you to copy only when necessary if your data hasn t changed in a given frame simply don t call a pfPass routine and you ll avoid the copy overhead When you do call a pfPass routine the data isn t immediately copied but is delayed until the next call to pfFrame The data is then copied into internal IRIS Performer memory and you re free to modify your passthrough data segment for the next frame Modifications to all libpf objects such as pfNodes and pfChannels are automatically passed through the processing pipeline so frame accurate behavior is guaranteed for these
352. g to 40 Open Inventor 157 256 285 loader C implementation 491 opera lighting 242 defined 522 operator delete 486 new 486 optimial pfGeoSet size 450 optimization database parameters 463 ordered rendering 24 organization of databases See databases orthogonal transformations 402 orthonormal transformations 402 411 overload definition 523 overrun definition 523 overrun frame 195 P parent of a node defined 523 partitions 144 pass through data defined 523 passthrough data 176 228 paths definition 523 search paths 65 393 through a simulated scene 8 through scene graph 168 perfly 3 198 254 426 433 definition 524 demo program 3 performance 66 costs lighting 454 multisampling 476 intersection 460 measurement 467 467 474 tuning database structure 461 466 graphics pipeline 453 456 guidelines specific 453 466 optimizations built in 449 452 overview 447 448 process pipeline 457 460 Reality Engine graphics 476 478 Performance Co Pilot 467 Performer See IRIS Performer Performer Terrain Utilities 298 pfBillboard 140 pfBillboard nodes 466 545 Index pfBox 408 pfChannel data structures See channels pfCylinder 409 pfDataPool data structures 388 multiprocessing with 227 pfdBuilder 36 284 pfDCS nodes 451 pfDispList data structures 355 pfFog data structures 234 350 See also fog pfFont 328 pfFrameStats data structures 425 See also
353. gement causes scaling of LODs in the database to meet the target frame rate with maximum scene detail The last three seconds of stress are shown in white while stress management is running Thus the channel statistics graph can be used to tune the upper and lower bounds of the hysteresis band for invoking stress management and for tuning LODs of objects in the database CPU Statistics CPU statistics illustrated with some other statistics in Figure 12 2 give you information on system usage and load The numbers shown correspond exactly to numbers given by osview they re updated every update period just like other statistics see Setting Update Rate on page 442 for information on how to change the update rate These numbers represent averages per second across all CPUs thus if one or more CPUs is busy with some other task the CPU statistics shown may not accurately reflect IRIS Performer CPU use Note that the top line of the CPU statistics panel shows the total number of frames during the last update period and the total time elapsed during that period Interpreting Statistics Displays 36 0 36 0Hz2 LIMIT APP_CULL_DRAW Draw 13 3ms tris 1701 verts 2540 Visible Geom tris 1701 lines 0 points 1 verts 2540 tStripTris 1655 tStrips 389 tris strip 4 25 prims GSet 15 9 prims GState 28 4 GSets GState 1 8 colors 139 normals 2426 texcoords 116 Attr Bytes 83536 gsets 10 flat 0 transp O hlighted 0 _ 4 15 14 12 82 7
354. ger which specifies the number of recursive subdivisions desired in data generation For example providing the pseudo filename 3 sponge to perfly will result in the Sponge loader being invoked and generating a sponge object using three levels of recursion resulting in a 35712 polygon database object The IRIS Performer sponge loader can be found in the usr share Performer src libflibpfdb libpfsponge directory pfdLoadFile uses the function pfdLoadFile_sponge to load Sponge format files into IRIS Performer run time data structures Star Chart Format The star format is a distillation of astronomical data from the Yale Compact Star Chart The sample data file usr share Performer data 3010 star contains data from the YCSC that has been reduced to a list of the 3010 brightest stars as seen from Earth and positioned as 3010 points of light on a unit radius sphere The IRIS Performer star loader can read this data and is provided as a convenience for making dusk dawn and night time scenes The loader is in the usr share Performer src libfibpfdb libpfstar directory Data ina star file is simply a series of ASCII lines with the s for star keyword followed by X Y and Z coordinates brightness and an optional name Here are the 10 brightest stars excluding Sol in the star format s 0 18746032 0 93921369 0 28763914 1 00 Sirius s 0 06323564 0 60291260 0 79529721 1 00 Canopus s 0 78377002
355. h You can think of the graphics pipeline as comprising three separate stages the pipeline runs only as fast as the slowest stage so improving the performance of the pipeline requires improving the slowest stage s performance The three stages are The host or CPU stage in which routines are called and general processing is done by the application This stage can be thought of as a software pipeline sometimes called the rendering pipeline itself comprising up to three sub stages the application cull and draw stages as discussed at length throughout this guide 447 Chapter 13 Performance Tuning and Debugging 448 The transformation stage in which transformation matrices are applied to objects to position them in space this includes matrix operations setting graphics modes transforming vertices handling lighting and clipping polygons The fill stage which includes clearing the screen and then drawing and filling polygons with operations such as Gouraud shading z buffering and texture mapping You can estimate your expected frame rate based on the makeup of the scene to be drawn and graphics speeds for the hardware you re using Be sure to include fill rates polygon transform rates and time for mode changes matrix operations and screen clear in your calculations Measure both the performance of complex scenes in your database and of individual objects and drawing primitive to verify your understand
356. h at compile time The names of the IRIS GL based libraries for IRIS Performer use the suffix _igl the names of the OpenGL based libraries end in _ogl For example to use the OpenGL version of libpf you would link to libpf_igl so For information on compiling and linking IRIS Performer applications see Compiling and Linking IRIS Performer Applications in Chapter 3 OpenGL OpenGL is a window system independent library of graphics functions Describing OpenGL in detail is beyond the scope of this guide to learn about OpenGL see the books mentioned in the Bibliography on page xxix Porting From IRIS GL to OpenGL If you have an IRIS Performer application that uses IRIS GL you can port it to use OpenGL with minimal work Most of what you need to do is port the window and event handling to use X OpenGL doesn t have any window or event routines The OpenGL Porting Guide provides more information on Graphics Libraries porting from IRIS GL to OpenGL and the sample applications distributed with IRIS Performer provide many examples of programs that compile and run with either IRIS GL or OpenGL The pfWindow Windowing Functions IRIS Performer provides window system independent window routines to allow greater portability of applications You can use these routines whether your application uses IRIS GL windowing mixed model IRIS GL X windowing or OpenGL with X For information about these window routines see the pf
357. h Paths 393 Math Routines 397 Vector Operations 397 Matrix Operations 399 Quaternion Operations 404 Matrix Stack Operations 407 Creating and Transforming Volumes 408 Defining a Volume 408 Creating Bounding Volumes 410 Transforming Bounding Volumes 411 Intersecting Volumes 412 Point Volume Intersection Tests 412 Volume Volume Intersection Tests 412 Creating and Working With Line Segments 414 Intersecting With Volumes 415 Intersecting With Planes and Triangles 416 Intersecting With pfGeoSets 416 General Math Routine Example Program 419 Statistics 425 Interpreting Statistics Displays 426 Status Line 427 Stage Timing Graph 427 Load and Stress 430 CPU Statistics 430 Rendering Statistics 432 Fill Statistics 432 xi Contents Collecting and Accessing Statistics in Your Application 433 Displaying Statistics Simply 434 Enabling and Disabling Statistics fora Channel 435 Statistics in libpr and libpf pfStats Versus pfFrameStats 435 Statistics Rules of Use 436 Reducing the Cost of Statistics 439 Statistics Output 440 Customizing Displays 442 Setting Update Rate 442 The pfStats Data Structure 443 Statistics Examples 443 13 Performance Tuning and Debugging 447 Performance Tuning Overview 447 How IRIS Performer Helps Performance 449 Draw Stage and Graphics Pipeline Optimizations 449 Cull and Intersection Optimizations 451 Application Optimizations 452 Specific Guidelines for Optimizing Performance 453 Graphics Pipeline Tu
358. hanStats IRIS Performer graphics routines graphics library routines More specific elaborations You should call configuration routines only from the application process and only after pfInit and before pfConfig pfInit must be the first IRIS Performer call except for those routines that configure shared memory see Memory Allocation in Chapter 10 Configuration routines don t take effect until pfConfig is called These are the configuration routines pfMultipipe pfMultiprocess pfMultithread pfHyperpipe You should call creation routines such as pfNewChan pfNewScene and pfAllocIsectData only in the application process after calling pfConfig or in a process which has an active pfBuffer There is no restriction on creating libpr objects like pfGeoSets and pfTextures pfDelete should only be called from the application or database processes pfAsyncDelete may be called from any process Read only routines that is the pfGet functions can be called from any IRIS Performer process However if a forked draw process queries a pfNode the data returned will not be frame accurate See Multiprocessing and Memory on page 226 223 Chapter 7 Frame and Load Control 224 Write routines functions that set parameters should be called only from the application process or a process with an active pfBuffer It is possible to call a write routine from the cull process but
359. hannel Use pfNewChan to create a new pfChannel and assign it to a pfPipe pfChannels are automatically assigned to the first pfPipeWindow of the pfPipe In the sample program the following statement creates a new channel and assigns it to pipe p chan pfNewChan p The primary function of a pfChannel is to define the view of a scene A view is fully characterized by a viewport a viewing frustum and a viewpoint The following sections describe how to set up the scene and view for a pfChannel Setting Up a Scene A pfChannel draws the pfScene set by pfChanScene A channel can draw only one scene per frame but can change scenes from frame to frame Other pfChannel attributes such as LOD modifications affect the scene These attributes are described in pfLOD Nodes in Chapter 5 Using Channels A pfChannel also renders an environmental model known as pfEarthSky A pfEarthSky defines the method for clearing the channel viewport before rendering the pfScene and also provides environmental effects including ground and sky geometry and fog and haze A pfEarthSky is attached to a pfChannel by pfChanESky Setting Up a Viewport A pfChannel is rendered by a pfPipe into its pfPipeWindow The screen area that displays a pfChannel s view is determined by the origin and size of the window and the channel viewport specified by pfChanViewport The channel viewport is relative to the lower left corner of the window and ranges fro
360. hapter 4 Setting Up the Display Environment 102 One situation that requires multiple channels occurs when inset views must appear within an image A simple example of this application is a driving simulator in which the screen image represents the view out the windshield If a rear view mirror is to be drawn it must overlay the main forward view to provide a separate view of the same database within the borders of the simulated mirror s frame Channels are physically rendered in the order that they are assigned to a pfPipeWindow on their parent pfPipe Channels upon creation are assigned to the end of the channel list of the first window of their pfPipe In the driving simulator example creating pipes and channels with the following structure creates two channels on a single shared pipeline pipeline pfGetPipe 0 frontView pfNewChan pipeline rearView pfNewChan pipeline In this case IRIS Performer s actual drawing order becomes 1 Clear frontView 2 Draw frontView 3 Clear rearView 4 Draw rearView This default ordering results in the rear view mirror image always overlaying the front view image as desired You can control and re order the drawing of channels within a pfPipeWindow with the pfInsertChan pwin where chan and pf MoveChan pwin where chan routines More details about multiple channels and multiple window are discussed in the next section When the host has multiple Geometry Pipe
361. hapter 6 and Sorting the Scene in Chapter 6 for more information on sorting Application Optimizations During the application stage IRIS Performer Divides the application process into two parts the latency critical section which includes everything between pfSync and pfFrame where last minute latency critical operations are performed before the cull of the current frame can start and the noncritical portion after pfFrame and before pfSync The critical section is displayed in the channel statistics graph drawn with pfDrawChanStats Provides an efficient mechanism to automatically propagate database changes down the process pipeline and provides pfPassChanData for passing custom application data down the process pipeline Minimizes overhead copying database changes to the cull process by accumulating unique changes and updating the cull once inside pfFrame This updated period is displayed in the MP statistics of the channel statistics graph drawn with pfDrawChanStats Provides a mechanism for performing database intersections in a forked process pass the PFMP_FORK_ISECT flag to pfMultiprocess and declare an intersection callback with pfIsectFunc Provides a mechanism for performing database loading and editing operations in a forked process such as the DBASE process pass the PFMP_FORK_DBASE flag to pf Multiprocess and declare an intersection callback with pfDBaseFunc Specific Guidelines for Optim
362. he cull which can give a visual check of what is actually being sent to the graphics subsystem Check for objects that are far from the viewing frustum which can indicate that the pfGeodes or pfGeoSets need to be broken up Additionally the rendering time of the GL object should be compared to the pfDraw rendering time to see if the pfGeoSets have enough triangles in them to not incur host overhead Alternately the view frustum can be made larger than that used in the cull to allow simple cull volume visualization during real time simulation The IRIS Performer sample program perfly supports this option Press the z key while in perfly to enable cull volume visualization and inspect the resulting images for excessive off screen geometric content Such content is a clear sign that the database could profitably be further subdivided into smaller components Specific Guidelines for Optimizing Performance The code fragment in Example 13 1 taken from the sample program usr share Performer src pguide libpf C bench c makes an IRIS GL object and then temporarily draws that instead of calling pfDraw Example 13 1 Drawing an Object Without Calling pfDraw if SharedFlags gt glObject MAKE _GL_OBJECT static have_obj 0 fprintf stderr Making object n have_ob delobj 1 makeobj 1 OpenGL glNewList pfDraw closeobj OpenGL glEndList SharedFlags gt glObject DRAW_GL_OBJECT have_obj
363. he models described here You can for instance build a specific path into the viewer to prevent the user from straying outside your model The path model is supported by a general path following system in the ibpfutil library Many simulation applications require path support for such objects as cars trucks and people in driver training software waiting aircraft both on the ground and in the air in flight simulation and opposing forces in military trainers Path support in libpfutil allows paths of varying speeds to be built from line segments and arcs with automatic fillet construction between segments for smooth transitions Instances The bench objects in the City Hall scene were designed using the database concept known as instancing in which a single geometric object such as a tree house car or in this case bench is used multiple times within a database at different locations and with different positions or scale factors In this case the instances have been flattened to improve performance each bench is now a separate object See Instancing in Chapter 5 for information on this topic Model Implementation and Database Format Loaders An important point about the implementation of this model is that the scene was created using a database modeler and is still in its original format This demonstrates the data fusion capability of IRIS Performer Databases need not be converted to a standard file format before being
364. he routine names The standard order of transformations for a hierarchical scene involves postmultiplying the transformation matrix for a child by the matrix for the parent For instance assume your scene involves a hand attached to an arm attached to a body To get a transformation matrix H for the hand postmultiply the arm s transformation matrix A by the body s B H AB To transform the hand object at location h in hand coordinates to body coordinates calculate h hH Matrix Operations Example 11 1 Matrix and Vector Math Examples test Rot of vl onto v2 test inversion of Affine Matrix pfVec3 vl v2 v3 pfMatrix ml MakeRandomVec3 v1 MakeRandomVec3 v2 pfNormalizeVec3 v1 pfNormalizeVec3 v2 pfMakeVecRotVecMat m1 vl v2 pfXformVec3 v3 vl ml AssertEqVec3 v3 v2 Arb Rot To a pfVec3 vl v2 v3 pfMatrix ml m2 m3 MakeRandomVec3 v3 pfMakeScaleMat m2 v3 0 v3 1 v3 2 pfPreMultMat m1 m2 MakeRandomVec3 v1 pfNormalizeVec3 v1 MakeRandomVec3 v2 pfNormalizeVec3 v2 pfMakeVecRotVecMat m1 vl v2 s pfLengthVec3 v2 pflengthVec3 v1 pfPreScaleMat ml s s s ml MakeRandomVec3 v1 pfNormalizeVec3 v1 MakeRandomVec3 v2 pfNormalizeVec3 v2 pfMakeVecRotVecMat m2 vl v2 MakeRandomVec3 v3 pfMakeTransMat m2 v3 0 v3 1 v3 1 403 Chapter 11 Math Routines Quaternion O
365. he viewing volume These distances describe the extent of the visual range in the view because geometry outside these boundaries is clipped meaning that it isn t drawn Use pfChanNearFar chan near far to specify the distance along the line of sight from the viewpoint to the near and far planes that bound the viewing volume These clipping planes are perpendicular to the line of sight For the best visual acuity choose these distances so that near is as far away as possible from the viewpoint and far is as close as possible to the viewpoint Minimizing the range between near and far provides more resolution for distance comparisons and fog computations Setting Up a Viewpoint A viewpoint describes the position and orientation of the viewer It is the origin of the viewing location the direction of the line of sight from the viewer to the scene being viewed and an up direction The default viewpoint is at the origin 0 0 0 looking along the Y axis with Z up and X to the right Use pfChanView chan point dir to define the viewpoint for the pfChannel identified by chan Specify the view origin for point in x y z world coordinates Specify the view direction for dir in degrees by giving the degree measures of the three Euler angles heading pitch and roll Heading is a rotation about the z axis pitch is a rotation about the x axis and roll is a rotation about the y axis The value of dir is the product of the rotations ROTy
366. here is exactly one window server on a machine but that is not required Libpr maintains a pfWSConnection for the current process By default this connection obeys the setting of the DISPLAY environment variable which can point to a window server on a local or a remote machine The current connection can be requested with pfGetCurWSConnection and can be set with pfSelectWSConnection It is recommended that whenever possible this connection be used to limit the total number of open connections pfOpenScreen is a convenient mechanism for opening a connection with a specified default screen pfOpenWSConnection allows you to specify the exact name specifying the desired target for the connection Both pfOpenScreen and pfOpenWSConnection allow you to specify if you would like the new connection to automatically be made the current libpr pfWSConnection this is recommended More pfWindow Examples Example 10 8 demonstrates creating a window that will support a desired fill statistics configuration This example is taken from the sample program usr share Performer src pguide libpr C fillstats c Statistics are the topic of Chapter 12 Statistics Example 10 8 Creating a Statistics Window int main void pfWindow win int bits sten Initialize Performer pfiInit Windows pfiInitState NULL set up number of bits needed for stats before window is made so that it will have the right number E7 pfQuery
367. hich allow visibility culling and drawing to run in parallel with the application process The number of processes created depends on the process model specified by a call to pfMultiprocess the number of processors and the number of pipes one by default call pfMultipipe to specify more than one pipe The order of the calls is important pfMultiprocess and pfMultipipe are effective only if called between pfInit and pfConfig The default is a single pipe running with one two separate draw process or three separate cull and draw processes processes depending on the number of processors on the machine When you run the application from the root login account pfConfig also sets nondegradable priorities for the processes to improve the consistency of the run time behavior For information on controlling multiple pipes see Using Pipes in Chapter 4 For information on multiprocessing see Successful Multiprocessing With IRIS Performer in Chapter 7 In addition to setting up shared memory pfInit initializes a high resolution clock by calling pfInitClock Depending on the hardware this may start up a process to service the clock The clock process consumes few system resources because it sleeps most of the time Setting Up the Basic Elements Setting Up a Pipe A pfPipe variable also called a pipe represents an IRIS Performer software graphics pipeline You gain access to a pipe using pfGetPipe for
368. hlights is provided by the projected texture capability of the pfLightSource node overload A condition where the time taken to process a frame is longer than the desired frame rate allows This causes the goal of a fixed frame rate to be unattainable and thus is an undesired situation overrun A synonym for overload in the context of fixed frame rate rendering pair wise morphing The geometric blending of two topologically equivalent objects Usually this is done by specifying weights for each object e g 90 of object A plus 10 of object B Each vertex in the resulting object is a linear interpolation between the vertices in the original object See morphing parent The IRIS Performer node directly above a given node is known as the parent node passthrough data Data which is passed down the steps in the rendering pipeline until it reaches a callback Such data provides the mechanism whereby an application can communicate information between the app cull and draw stages in a pipelined manner without code changes in single CPU and multiprocessing applications path A series of nodes from a scene graph s root down to a specific node defines a path to that node When there are multiple paths to a node and thus the scene graph is really a graph rather than a tree this path can be important when interpreting an intersection or picking request For example if a car 523 Glossary 524 model uses instancing for th
369. ications to retrieve file data during real time operation This file I O is very similar to the standard IRIX file I O functions Memory Allocation pfMalloc pfDataPool IRIS Performer includes routines to allocate memory from the application process heap or from shared memory arenas Shared arenas must be used when multiple processes need to share data The application can create its own shared memory arenas or use pfDataPools pfDataPools are shared arenas that can be shared by multiple processes Applications can allocate blocks of memory within pfDataPools which can be individually locked and unlocked to provide mutual exclusion between unrelated processes High Resolution and Video Rate Clocks pfGetTime pfVClock IRIS Performer includes high resolution clock and video interval counter routines pfGetTime returns the current time at the highest resolution that the hardware supports Processes can either share synchronized time values with other processes or have their own individual clocks The video interval counter is tied to the video retrace rate and can synchronize a process with any multiple of the video rate this mechanism is the basis for producing fixed frame rates Intuitive Interface All the IRIS Performer commands have intuitive names that describe what they do These mnemonic names make it easy for you to learn and remember the commands The names may look a little strange to you if you re unfamiliar with this t
370. icitly disable lighting Then attach different pfMaterials and pfTextures to pfGeoStates to define specific state combinations Note Caution should be used when enabling modes in the global state These modes may have cost even when they have no visible effect Therefore geometry that cannot use these modes should have a pfGeoState that explicitly disables the mode Modes to be especially careful of include the texturing enable and transparency Graphics State You specify that a pfGeoState should inherit state elements from the global default with pfGStateInherit gstate mask mask is a bitmask of tokens that indicates which state elements to inherit These tokens are listed in the Rendering Modes Rendering Values and Rendering Attributes sections of this chapter For example PFSTATE_ENLIGHTING PFSTATE_ENTEXTURE makes gstate inherit the enable modes for lighting and texturing A state element ceases to be inherited when it is set in a pfGeoState Rendering modes values and attributes are set with pfGStateMode pfGStateVal and pfGStateA ttr respectively For example to specify that gstate is transparent and textured with treeTex use pfGStateMode gstate PFSTATE_TRANSPARENCY PFTR_ON pfGStateAttr gstate PFSTATE EXTURE treeTex Applying pfGeoStates Use pfApplyGState to apply the state encapsulated by a pfGeoState to the Geometry Pipeline The effect of applying a
371. iewing matrix is initialized to a two dimensional one to one mapping from eye coordinates to window coordinates e the model matrix is initialized to the identity matrix and made the current GL matrix e backface removal is enabled e smooth shading is enabled Using pfPipeWindows e if the current graphics hardware platform supports multisampling multisampled antialiasing will be enabled with pfAntialias PFAA_ON e a default modulating texture environment is created e adefault lighting model is created Custom framebuffer configuration for a pfPipeWindow can be specified with pfPWinFBConfigA ttrs pfPWinFBConfig and pfChoosePWinFBConfig These routines have identical functionality as each of the corresponding pfWindow routines However the function pfChoosePWinFBConfig has the constraint that it be called in the draw process because it creates and stores internal data from the window server that must be kept local to the process in which it is called Table 4 2 lists the different pfPipeWindow routines and describes multiprocessing constraints The flexibility in changing the framebuffer configuration of a pfPipeWindow is GL dependent IRIS GL supports reconfiguration of the framebuffer However in GLX or OpenGL X windows it is considerably trickier The main window can remain in place but structures under it must be switched or replaced If multiple framebuffer configurations are likely to be desired multiple gr
372. ight point color pfSetVec4 red 1 0f 0 0f 0 0f 1 0f pfLPointColor lp red set the direction the light points face pfLPointRot lp 270 0f 30 0f 0 0f Nag Set the position of light point 5 pfSetVec3 pos 10 0f 10 0f 0 0f pfLPointPos lp 5 pos pfLightSource Nodes A pfLightSource unlike a pfLightPoint provides light for a scene s geometry but is itself invisible 133 Chapter 5 Nodes and Node Types 134 Illuminating the geometry in a scene graph requires a light source which the graphics hardware uses to compute surface shading While the libpr primitive pfLight see Lighting on page 348 provides a hardware light source it isn t a pfNode and so cannot benefit from the features provided by a scene graph such as transformation hierarchy switches and sequenced animations The pfLightSource node allows you to add lighting information to your scene graph pfLightSource is multiply inherited it s derived from both pfNode and pfLight so you can use a pfLightSource as an argument to a function that requires a pfNode or pfLight as illustrated in Example 5 8 Example 5 8 pfLightSource Pointers and Multiple Inheritance pfLightSource lsource pfNewLSource Set color to red pfLightColor lsource 1 0f 0 0f 0 0f Add light source to scene pfAddChild scene lsource In this example source is the pfLight argument to pfLightColor and the pfNod
373. ightOff pfLightSources are treated specially when drawing a scene graph All paths leading to pfLightSources in a scene are traversed before the scene is traversed For information about paths see Paths Through the Scene Graph in Chapter 6 This special initial traversal guarantees that the graphics hardware will be configured with all pfLightSources so that they will affect all geometry in the scene In addition these light sources are set up before the channel draw callback is invoked so they affect all custom geometry rendered by the application both before and after pfDraw See pfNode Cull and Draw Callbacks in Chapter 6 for more on callbacks By default pfLightSource traversal is enabled and carried out by the cull traversal If you wish to bypass this traversal and thereby ignore all pfLightSources in your scene then set the PRCULL_IGNORE_LSOURCES bit in the mode passed to pfChanTravMode for the PFTRAV_CULL traversal A pfLightSource has no default bounding volume though you can assign it one with pfNodeBSphere If a pfLightSource is assigned a bounding volume it becomes subject to view frustum culling and will be discarded if it is completely outside the view frustum of the pfChannel If the light source is found to be within the view frustum or it has an empty bounding volume the default the pfLightSource will affect everything in view By setting the appropriate bounding sphere it is possible to roughly s
374. image that corresponds to that of the base texture 477 Chapter 13 Performance Tuning and Debugging Other Tips Two final notes on RealityEngine performance e Changing the width of antialiased lines and points is expensive e pfMtlColorMode which calls the IRIS GL function Imcolor or the OpenGL function glColorMaterial has a huge performance benefit 478 Chapter 14 Pro gramming with C This chapter discusses the differences in programming using the C and C programming interfaces Chapter 14 Programming with C This chapter provides an overview of some of the differences between programming IRIS Performer using the C Application Programming Interface C API rather than the C language Application Programming Interface C API which is described in the earlier chapters of this guide Overview Although this guide uses the C API throughout the C API is in every way equal and in some cases superior in functionality and performance to the C API Every function available in the C API is available in the C API All of the C API routines tightly associated with a class have a corresponding member function in the C API e g pfGetDCSMat becomes pfDCS getMat Routines not closely associated with a class are the same in both APIs Examples include high level global functions such as pfMultiprocess and pfFrame and low level graphics functions such as pfAntialias Most of the rout
375. images at a consistent chosen frame rate Fixed frame rates are a central theme of visual simulation and are supported in IRIS Performer via the PFPHASE_LOCK and PFPHASE_FLOAT modes Maintaining a fixed frame rate in databases of varying complexity is difficult and is the task of IRIS Performer stress processing which changes LOD scales based in measured system load flatten Flattening consists of taking multiple instances of a single object and converting them into separate objects deinstancing and then applying any static transformations defined by pfSCS nodes to the copied geometry this action improves performance at a cost in memory space flimmering The visual artifact associated with improperly drawing coplanar Z buffered geometry The term is derived from the German verb flimmern which is has synonyms flitter flicker sparkle twinkle and vibrate as in die Augen flimmern mir my eyes are swimming One way to understand flimmering is to consider the screen space interpolation of Z depth values wherein a discrete difference of depth must be interpolated across a discrete number of pixels or sub pixels When two polygons that would be coplanar in an infinite precision real number context are considered in this discrete interpolation space it is clear that the interpolated depth values will differ when the delta Z to delta pixels ratios are relatively prime The image that results is essentially a Moir pattern showing the
376. in Figure 9 1 shows several of the BIN format objects provided in the IRIS Performer sample data directory 271 Chapter 9 Importing Databases 272 Figure 9 1 BIN Format Data Objects The source code for the BIN format importer pfdLoadFile_bin is provided in the file pfbin c This code shows how easy it can be to implement an importer Since pfdLoadFile_bin is based on the pfdBuilder utility function it will build efficient triangle strip pfGeoSets from the quadrilaterals of a given BIN file The BIN format has the following structure 1 A4 byte magic number 0x5432 which identifies the file as a BIN file 2 A4 byte number that contains the number of vertices which is four times the number of quadrilaterals 3 Four bytes of zero 4 A list of polygon data for each vertex in the object The data consists of three floating point words of information about normals followed by three floating point words of vertex information Description of Supported Formats The BIN format uses these data structures typedef struct float normal 3 float coordinate 3 Vertex typedef struct long magic long vertices long zero Vertex vertex 1 BinFile pfdLoadFile uses the function pfdLoadFile_bin to import data from BIN format files into IRIS Performer run time data structures The pfdLoadFile_bin function composes a random color for each file it reads The chosen color has red green and blue
377. in the pfGeoSet and the triangle index within the primitive for tristrips and quads primitives as well as the actual triangle vertices You can also extract information from a pfHit object using pfQueryHit and pfMQueryHit See Intersection Requests pfSegSets and Intersection Return Data pfHit Objects in Chapter 6 for more information about pfSegSets and pfHit objects The principal difference between those routines and pfGSetlIsectSegs is that with pfGSetIsectSegs information concerning the libpf scene graph such as transformation geode name and path is never used Two types of intersection testing are possible as shown in Table 11 11 Table 11 11 Available Intersection Tests Test Name Function PFTRAV_IS_GSET Intersect the segment with the bounding box of the pfGeoSet PFTRAV_IS_PRIM Intersect the segment with the polygon based primitives inside the pfGeoSet You can use PFTRAV_IS_GSET for crude collision detection and PFTRAV_IS_PRIM for fine grained testing You can enable both bits and dynamically choose whether to go down to the primitive level by using a discriminator callback see Discriminator Callbacks pfGSetIsectSegs performs only primitive level testing for pfGeoSets consisting of triangles PFGS_TRIS quads PFGS_QUADS and tristrips PFGS_TRISTRIPS and all are decomposed into triangles Intersection Masks Each pfGeoSet has an intersection mask that you set using pfGSet
378. in the previous subsegment and then checking intersections e The time spent waiting while the cull process copies updated information from the application and starts the cull stage for the now finished frame drawn as a low thin line The cull stage is divided into only two subsegments e The time spent receiving updates from the application in some multiprocessing models this overlaps with the last subsegment of the application stage e The time spent in the channel cull callback including time spent in pfCull drawn as raised line Interpreting Statistics Displays The draw stage has four subsegments The time spent in the channel draw callback before the call to pfDraw a very short thick dark raised segment This will include the time for your call to pfClearChan However under normal circumstances this segment shouldn t be visible at all Operations taking place during this time should only be latency critical This line should be extremely short unless you have a very good reason The time spent in pfDraw the main thick segment The time spent in the channel draw callback after pfDraw another short thick dark raised segment Additionally the last channel drawn on the pipe will include the time for the graphics pipeline to finish its drawing Even if you have no operations after pfDraw in you draw callback this line for the last channel might look quite long particularly if you are very fill li
379. indices which indicates that the indices are sequential from the initial value of zero The choice of indexed or direct components applies to an entire pfGeoSet that is all of the supplied components within one pfGeoSet must use the same method However you can emulate partially indexed pfGeoSets by using indexed specification and making each nonindexed attribute s index list be a single shared identity mapping index array whose elements are 0 1 2 3 N 1 where N is the largest number of attributes in any referencing pfGeoSet You can share the same array for all such emulated pfGeoSets The direct method avoids one level of indirection and may have a performance advantage compared with indexed specification for some combinations of CPU and graphics subsystem Note it is highly recommended that pfMalloc be used to allocate your arrays of attribute data This will allow IRIS Performer to reference count the arrays and delete them when appropriate It will also allow you to easily put your attribute data into shared memory for multiprocessing by specifying an arena such as pfGetSharedArena to pfMalloc While perhaps convenient it is very dangerous to specify pointers to static data for pfGeoSet attributes Early versions of IRIS Performer permitted this but it is strongly discouraged and may have undefined and unfortunate consequences 325 Chapter 10 libpr Basics Figure 10 2 pfGeoSet Structure 326 Geometr
380. indow The graphics drawable and graphics context of an alternate configuration window of a pfWindow can be closed with pfCloseWinGL This can be called on the base window in which case the active alternate configuration window s GL window and context will be closed or it can be called on the alternate configuration window pfWindow directly The main Windows parent window will remain on the screen and a new alternate configuration window can be applied to it or pfOpenWin can be called to create a new graphics window and context There are some modes you can set that can effect the general look and behavior of your window and alternate configuration windows These boolean modes can be individually set and changed at any time with pfWinMode and the tokens in Table 10 22 Table 10 22 pfWinMode Tokens PFWIN_ Token Description NOBORDER Window will be without normal window system border HAS_OVERLAY Overlay alternate configuration window will be managed by the pfWindow pfOpenWin will automatically create an overlay window if one has not already been set pfWinIndex win PFWIN_OVERLAY_WIN will also automatically create and open an overlay window if one has not already been set This mode only has effect for X windows HAS_STATS Statistics alternate configuration window will be managed by the pfWindow pfOpenWin will automatically create a statistics window if one has not already been set pfWinIndex win PFWIN_OVER
381. indow will open with position undefined for the user to place If the x or y components of the size are 1 the window will open with both position and size undefined the default for the user to place and stretch The X window manager may override negative origins and place the window at 0 0 If the window is already opened when pfWinOriginSize is called the window will be reconfigured to the specified origin and size upon the next pfSelectWin Similarly pfWinFullScreen will cause a window to open as full screen or to become full screen upon the next call to pfSelectWin A full screen window will have its border automatically removed so that the drawing area truly gets the full rendering surface The routines for querying the position and size work a bit differently than the pattern established by the rest of libpr get and set pairs of routines This is because a user may change the origin or size independently of the program and under certain conditions querying the true current X window size and origin can be expensive pfGetWinOrigin and pfGetWinSize will always be fast and will return the last explicitly set origin and size such as by pfOpenWin pfWinOriginSize or Windows pfWinFullScreen If the window origin or size has been changed but not through a pfWindow routine the values returned by pfGetWinOrigin and pfGetWinSize may not be correct pfGetWinCurOriginSize will return an accurate size and origin relat
382. ines associated with a class can be divided into three categories setting an attribute getting attribute and acting on the object In the C API sets were usually expressed as pf lt Class gt lt Attribute gt gets as pfGet lt Class gt lt Attribute gt and simple actions as pf lt Action gt lt Class gt where lt Class gt is the abbreviation for the full name of the class In some cases where there was no room for confusion or this usage was awkward the routine names were shortened e g pfAddChild The principal difference in the naming of member functions in the C API and the corresponding routine name in t he C language API is in the naming of member functions where the pf prefix and the lt Class gt identifier are dropped In addition the word set or get is prefixed when attribute values are being set or retrieved Hence value setting functions are usually 481 Chapter 14 Programming with C Class Taxonomy 482 have names of the form pfClass set lt Attribute gt value getting functions are named pfClass get lt Attribute gt and actions appear as pfClass lt Action gt Table 14 1 Corresponding routines in the C and C API C Routine C Member Function Description pfMtlColor pfMaterial setColor Set material color pfGetMtlColor pfMaterial getColor Get material color pfApplyMtl pfMaterial apply Apply the material Note Member function whose names begin with pf_
383. ing ball and line of sight visibility Table 6 4 matches database classes with the pfNodeTravMask and pfGSetIsectMask values used to support the traversal tests listed above Table 6 4 Database Classes and Corresponding Node Masks Database Class Node Mask Water 0x01 Ground 0x02 Pier 0x04 Clouds 0x08 Intersection Traversal Once the mask values at nodes in the database have been set intersection traversals can be directed by them For example the line segments for ship collision detection should be sensitive to the water ground and pier while a those for a bowling ball would ignore intersections with water and the clouds testing only against the ground and pier Line of sight ranging should be sensitive to all the geometry in the scene Table 6 5 lists the traversal mask values and mask representations that would achieve the proper intersection tests Table 6 5 Representing Traversal Mask Values Intersection Class Mask Value Mask Representation Ship 0x07 Water Ground Pier Bowling ball 0x06 Ground Pier Line of sight ranging 0x0f Water Ground Pier Clouds The intersection traversal prunes a node as soon as it gets a zero result from doing a bitwise AND of the node intersection mask and the traversal mask specified by the pfSegSet s isectMask field Thus all nodes in the scene graph should normally be set to be the bitwise OR of the masks of their children After setting the class specifi
384. ing of the performance requirements Use the IRIS Performer diagnostic statistics to evaluate how long each stage takes and how much it does See Chapter 12 Statistics for more information These statistics are referred to frequently in this chapter Use system tools to help profile and analyze your application The IRIS GL glprof utility described in Using glprof to Find Performance Bottlenecks on page 469 will profile the rendering of an IRIS GL programs and show what was drawn and help figure out what stage of the graphics hardware pipeline is the significant bottleneck Tuning an application is an incremental process As you improve one stage s performance bottlenecks in other stages may become more noticeable Also don t be discouraged if you apply tuning techniques and find that your frame rate doesn t change frame rates only change by a field at a time which is to say in increments of 16 67 milliseconds for a 60 Hz display while tuning may provide speed increases of finer granularity than that To see performance improvements that don t actually increase frame rate look at the times reported by IRIS Performer statistics on the cull and draw processes see Chapter 12 for more information See the graphics library books listed in the Bibliography on page xxix for information about how to get peak performance from your graphics hardware beyond what IRIS Performer does for you How IRIS Performer Helps
385. ing the object begin keyword such a name is used by the loader for the name of the corresponding IRIS Performer node Polygon definitions are bracketed by the keywords polygon begin and polygon end and contain three or more vertex definitions Description of Supported Formats Vertex definitions are introduced by the vertex keyword and define the X Y and Z coordinates of a single vertex The following is a PHD format definition of a unit radius tetrahedron centered at the origin of the coordinate axes It is derived from the database developed by Andrew Hume but has since been translated scaled and reformatted file 000 phd object begin tetrahedron polygon begin vertex 0 090722 0 366647 0 925925 vertex 0 544331 0 628540 0 555555 vertex 0 453608 0 890430 0 037037 polygon end polygon begin vertex 0 907218 0 104757 0 407407 vertex 0 090722 0 366647 0 925925 vertex 0 453608 0 890430 0 037037 polygon end polygon begin vertex 0 090722 0 366647 0 925925 vertex 0 907218 0 104757 0 407407 vertex 0 544331 0 628540 0 555555 polygon end polygon begin vertex 0 453608 0 890430 0 037037 vertex 0 544331 0 628540 0 555555 vertex 0 907218 0 104757 0 407407 polygon end object end pfdLoadFile uses the function pfdLoadFile_phd to load PHD format files into IRIS Performer run time data structures The pfdLoadFile_phd function composes a color with red green and blue components unifo
386. insPt 412 pfBoxExtendByBox 410 pfBoxExtendByPt 410 pfBoxlsectSeg 415 pfBufferAddChild 221 511 pfBufferClone 221 511 pfBufferRemoveChild 221 511 pfBuildPart 144 145 pfCBufferChanged 390 pfCBufferConfig 389 391 pfCBufferFrame 390 391 pfChanBinOrder 167 510 pfChanBinSort 167 510 pfChanESky 93 231 236 pfChanFOV 94 pfChanGState 36 450 pfChanLODAttr 194 pfChanLODLODStateIndex 203 pfChanLODStateList 203 pfChanNearFar 95 pfChanNodelsectSegs 179 pfChanPick 185 pfChanScene 92 125 pfChanShare 82 106 157 pfChanStatsMode 434 pfChanStress 193 pfChanStressFilter 193 212 pfChanTravFunc 168 176 228 pfChanTravFuncs 231 pfChanTravMask 170 pfChanTravMode 162 169 170 452 462 pfChanView 95 97 pfChanViewMat 97 pfChanView Offsets 105 pfChanViewport 64 pfChooseFBConfig 370 pfChoosePWinFBConfig 83 88 pfChooseWinFBConfig 369 370 pfClear 224 pfClearChan 177 231 429 455 pfClearStats 437 pfClipSeg 415 416 pfClockMode 384 pfClockName 385 pfClone 221 pfCloseDList 355 pfCloseFile 391 pfClosePWin 88 90 pfClosePWinGL 88 pfCloseWin 372 pfCloseWinGL 372 pfCombineVec3 398 pfConfig 59 62 76 218 220 391 474 493 495 pfConfigPWin 85 90 459 pfConfigStage 76 459 pfConjQuat 405 pfCopy 45 49 328 387 441 pfCopyFStats 436 441 pfCopyGSet
387. into fourteen chapters and an appendix Chapter 1 Getting Acquainted With IRIS Performer takes you on a tour of some demonstration databases using sample IRIS Performer applications Chapter 2 IRIS Performer Basics provides a brief overview of IRIS Performer its features applications and component libraries as well as a brief survey of general visual simulation techniques Chapter 3 Building a Visual Simulation Application outlines the structure of a visual simulation application Chapter 4 Setting Up the Display Environment describes how to set up rendering pipelines windows and channels cameras Chapter 5 Nodes and Node Types describes the data structures used in IRIS Performer s memory based scene definition databases Chapter 6 Database Traversal explains how to manipulate and examine a scene graph Chapter 7 Frame and Load Control explains how to control frame rate synchronization and dynamic load management This chapter also discusses the load management techniques of multiprocessing and level of detail Chapter 8 Creating Visual Effects describes special features used in visual environments including spotlights shadows realistic earth and sky models and morphing Chapter 9 Importing Databases describes database formats and sample conversion utilities Chapter 10 libpr Basics discusses the foundation on which IRIS Performer is ba
388. ion development task that IRIS Performer helps you create the visual part what you see when you look out the window But there s more to a simulation of reality than just visuals Purely visual simulations of travel have much the same feel whether the simulation is of a boat a car a plane or a magic carpet In such simulations there s no nonvisual sensory input at all the user simply watches scenery move past IRIS Performer leaves the nonvisual aspects the feel of the simulation up to you You determine the vehicle dynamics and construct an apparatus or create code to mimic its behavior You develop a method for manifesting the physical sensation of how your simulation relates to its environment and responds to stimuli When you integrate physical aspects of a simulator with the real time visuals created with IRIS Performer the result can be a complete sensory environment both visual and physical creating a convincing simulation of reality Since IRIS Performer puts the tools for rapid development of real time visuals into your hands you can spend more time developing the physical part of the simulation Another aspect of IRIS Performer that lies below the surface of the demos is its ability to accelerate graphics to top rated performance levels on Silicon Graphics hardware This means that IRIS Performer puts a virtual Silicon Graphics hardware and software expert at your fingertips providing all the tools you need to custom t
389. ion of pfLODStates Ultimately a LODs switch range without regard to system stress can be computed as follows switch_range i range i LODStateRangeScale ChannelLODStateRangeScale LODStateRangeOffset ChannelLODStateRangeOffset Level of Detail Management ChannelLODScale ChannelSizeAndFOVFactor If IRIS Performer channel stress processing is active the computed range is modified as follows switch_range i ChannelLODStress LODStateRangeStressScale ChannelLODStateRangeStressScale LODStateRangeStressOffset ChannelLODStateRangeStressOffset Example 7 2 illustrates how to set LOD ranges The code in this example is derived from usr share Performer src sample apps C lod lod c the main source module for the sample program lod Example 7 2 Setting LOD Ranges setLODRanges sets the ranges for the LOD node The ranges from 0 to NumLODs are equally spaced between min and max The last range which determines how far you can get from the object and still see it is set to visMax ky void setLODRanges pfLOD lod float min float max float visMax tit lars float range rangelInc rangeInc max min ViewState gt shellLOD 1 for range min i 0 i lt ViewState gt shellLOD i ViewState gt range i range pfLODRange lod i range range rangelInc ViewState gt range i visMax pfLODRange lod i v
390. is supported only on RealityEngine graphics systems Note that the actual blend or fade distance used by Performer can also be adjusted by the LOD priority structures called pfLODStates pfLODStates hold an offset and scale for the size of transition zones as well as an offset and scale for how system stress can affect the size of the transition zones See Level of Detail States on page 202 for more information on pfLODStates Note also that there exists a global LOD transition scale on a per channel basis that can affect all transition distances uniformly Thus for an LOD with 5 switch ranges RO R1 R2 R3 R4 to switch between four models MO M1 M2 M3 there are 5 transition zones TO fade in MO T1 blend between MO and M1 T2 blend between M1 and M2 T3 blend between M2 and M3 T4 fade out M3 The actual fade distances without regard to channel stress are as follows Level of Detail Management fadeDistance i transition i LODStateTransitionScale ChannelLODStateTransitionScale LODStateTransitionOffset ChannelLODStateTransitionOffset ChannelLODFadeScale If Performer management of channel stress is turned on then the above fade distance is modified as follows fadeDistance i ChannelStress LODStateTransitionStressScale ChannelLODStateTransitionStressScale LODStateTransitionStressOffset ChannelLODStateTransitionStressOffset Terrain Level of
391. isMax generateShellLODs creates shell LOD nodes according to the parameters specified in the shared data structure f 205 Chapter 7 Frame and Load Control 206 void generateShel1lLODs void int i pfGroup grp pfVec4 clr long numLOD ViewState gt shellLOD long numPnts ViewState gt shellPnts long numPcs ViewState gt shellPcs for i 1 i lt numLOD i if ViewState gt shellColor SHELL _COLOR_SING pfSetVec4 clr 0 9f O 1f 0 1f 1 0f else set the color highest level RED middle LOD GREEN lowest LOD BLUE pfSetVec4 clr i lt long floor double numLOD 2 0f 2 0 numLOD i 1 0 2 0 numLOD O2 0 i lt long floor double numLOD 2 2 0 numLOD i 1 2 0 numLOD i 2 0f i lt long floor double numLOD 2 0 0E 2 0f numLOD i 1 0 LOENG build a shell GeoSet grp createShell numPcs numPnts ViewState gt shellSweep amp clr ViewState gt shellDraw normalizeNode pfNode grp add geode as another level of detail node pfAddChild ViewState gt LOD grp simplify the geometry but don t have less than 4 points per circle or less than 3 pieces numPnts numPnts gt 7 numPnts 4 4 numPcs numPcs gt 6 numPcs 4 3 Level of Detail Management ViewState gt LOD pfNewLOD
392. istics This chapter first explains some of the complex graphical displays and then discusses how to display statistics from a libpf based application Subsequent sections explain how to access and manipulate statistics from within an application Topics include enabling and disabling statistics classes printing querying and copying statistics data as well as some basic examples showing common uses of statistics At the end of this chapter is a discussion of the different statistics classes for libpr and libpf along with details of their use 425 Chapter 12 Statistics Interpreting Statistics Displays 426 Many types of statistics can be displayed in a channel Most such displays consist simply of labeled numbers and are fairly self explanatory however some of the displays such as the stage timing graph warrant further explanation IRIS Performer tracks the time spent in the application cull and draw stages of the rendering pipeline The basic statistics display shows a timing graph for each stage of the past several frames as well as showing the current frame rate and load information This profiling diagram is useful for optimizing both the database and application structure Figure 12 1 shows a sample stage timing graph from an IRIS Performer demo program It might be helpful to refer to a running example as well by turning on a statistics display in perfly for instance while reading this section 36 0 36 0Hz2 LI
393. ists in Chapter 10 However direct graphics library calls can be made safely only in draw function callbacks because only the draw process of multiprocess IRIS Performer configurations is known to be associated with a window Example 6 2 shows some sample node callbacks Example 6 2 pfNode Draw Callbacks void LoadScene char filename pfScene scene pfNewScene pfGroup root pfNewGroup pfGroup reflectiveGeodes NULL root pfdLoadFile filename reflectiveGeodes ReturnListofGeodesWithReflectiveMaterials root Use a node callback in the Draw process to turn on and off graphics library environment mapping before and after drawing all of the pfGeodes that have pfGeoStates with reflective materials he pfNodeTravFuncs reflectiveGeodes PFTRAV_DRAW pfdPreDrawReflMap pfdPostDrawReflMap This callback turns on graphics library environment mapping Because it changes graphics state it must be a Draw process node callback long pfdPreDrawReflMap pfTraverser trav void data 173 Chapter 6 Database Traversal Process Callbacks 174 texgen TX_S G_SPHEREMAP 0 texgen TX_T G_SPHEREMAP 0 texgen TX_S G_ON NULL texgen TX_T G_ON NULL return NULL This callback turns off graphics library environment mapping Because it also changes graphics state it also must be a Draw process node callba
394. it The memory is freed when the last process referring to the datapool pfDelete s it CycleBuffers A multiprocessed environment often requires that data be duplicated so that each process can work on its own copy of the data without adversely colliding with other processes pfCycleBuffer is a memory structure which supports this programming paradigm A pfCycleBuffer consists of one or more pfCycleMemories which are equally sized memory blocks The number of pfCycleMemories per pfCycleBuffer is global and is set once with pfCBufferConfig and is typically equal to the number of processes accessing the data Each process has a global index set with pfCurCBufferIndex which indexes a pfCycleBuffer s array of pfCycleMemories When each process has a different index and its own address space mutual exclusion is ensured if the process limits its pfCycleMemory access to the currently indexed one The cycle term of pfCycleBuffer refers to its suitability for pipelined multiprocessing environments where processes are arranged in stages like an assembly line and data propagates down one stage of the pipeline each frame In this situation the array of pfCycleMemories can be visualized as a circular list Each stage in the pipeline accesses a different pfCycleMemory and at frame boundaries the global index in each process is advanced to the next pfCycleMemory in the chain In this way data changes made in the head of the pipeline are pro
395. itations maximizing visual cues while minimizing the polygon count in a database is often an important aspect of database development Level of detail processing is one of the most beneficial tools available for managing database complexity for the purpose of improving display performance Level of Detail Management The basic premise of LOD processing is that objects that are barely visible either because they are located a great distance from the eyepoint or because atmospheric conditions reduce visibility don t need to be rendered in great detail in order to be recognizable This is in stark contrast to brutishly mandating that all polygons be rendered regardless of their contribution to the visual scene Both atmospheric effects and the visual effect of perspective decrease the importance of details as range from the eyepoint increases The predominant visual effect of distance is the perspective foreshortening of objects which makes them appear to shrink in size as they recede into the distance To save rendering time objects that are visually less important in a frame can be rendered with less detail The LOD approach to optimizing the display of complex objects is to construct a number of progressively simpler versions of an object and to select one of them for display as a function of range This requires you to create multiple models of an object with varying levels of detail You also must supply a rule to determine how much det
396. ive to the pfWindow parent For pure IRIS GL windows this will also be reasonably fast however for X windows it will be expensive and should not be done in real time situations The parent of an IRIS GL window is always the screen but not so with X windows pfGetWinCurScreenOriginSize will return the size and the screen relative origin of the pfWindow If the pfWindow is an X window this command will be quite expensive and is not recommended accept for rare use or initialization purposes pfPipeWindows discussed in Chapter 4 Setting Up the Display Environment take advantage of the multiprocessed libpf environment to always be able to return an accurate window size and origin relative to the window parent A process separate from the rendering process is by the window manager of changes in the pfPipeWindow s size in an efficient manner without impacting the window system or the rendering process However even for pfPipeWindows getting a screen relative origin can be an expensive operation Hint Users are strongly encouraged to write programs that are window telative and do not depend on knowing the current exact location of a window relative to its parent or screen Configuring the framebuffer of a pfWindow IRIS Performer provides a default framebuffer configurations for the current graphics hardware platform for the standard window types normal rendering statistics stats and overlay You may want to define your own fra
397. izing Performance Specific Guidelines for Optimizing Performance While IRIS Performer provides inherent performance optimization there are specific techniques you can use to increase performance even more This section contains some guidelines and advice pertaining to database organization code structure and style managing system resources and rules for using IRIS Performer Graphics Pipeline Tuning Tips Tuning the graphics pipeline requires identifying and removing bottlenecks in the pipeline You can remove a bottleneck either by minimizing the amount of work being done in the stage that has the bottleneck or in some cases by reorganizing your rendering to more effectively distribute the workload over the pipeline stages This section contains specific tips for finding and removing bottlenecks in each stage of the graphics pipeline For more information on this topic refer to the graphics library documentation see The IRIS GL and OpenGL Graphics Libraries on page xxx for information on ordering these books Host Bottlenecks Here are some ways to minimize the time spent in the host stage of the graphics pipeline e Function calls loops and other programming constructs require a certain amount of overhead To make such constructs cost effective make sure they do as much work as possible with each invocation For instance drawing a pfGeoSet of triangle strips involves a nested loop iterating on strips within the set
398. ject allocation 486 from unshared pfObject allocation 486 Coryphaeus Designer s Workbench 15 DWB format 37 252 counter video 34 385 counting basic block 467 CPU statistics 430 critically damped definition 513 CULL 73 culling 6 callbacks 158 definition 514 efficient 163 multithreading 217 traversal 158 traversals See traversals cull overlap draw multiprocessing model 216 cull volume visualization definition 513 cumulative statistics 443 See also statistics current statistics 443 See also statistics cycle buffers 228 389 cylinders as bounding volumes 409 bounding 460 D DAG See directed acyclic graph 30 database builder 36 database construction 36 database loaders 157 491 database paging 163 220 definition 514 databases 28 creating 64 formats See formats importing 8 14 251 optimization 462 organization 156 163 See also traversals traversals 153 187 databases as programming languages 20 data files 58 data fusion 8 defined 514 datapools See pfDataPool data structures Davis Tom xxx dbx 475 See also debugging DCS See pfDCS nodes debugging dbx 475 gldebug 468 guidelines 474 475 ogldebug 468 shared memory and 474 debug libraries definition 514 decal geometry definition 514 decals See coplanar geometry deleting objects 46 deletion 31 demonstration programs xxviii depth buffer shadows 85 depth complexity
399. k to a value pfGetVClock Get the current count pfVClockSync Block the calling process until a count is reached When using pfVClockSync the calling routine is blocked until the current count modulo rate is offset The VClock functions can be used to synchronize several channels or pipelines Memory Allocation You can use IRIS Performer memory allocation functions to allocate memory from the heap from shared memory and from datapools 385 Chapter 10 libpr Basics 386 Table 10 24 lists and describes the IRIS Performer shared memory routines Table 10 24 Memory Allocation Routines Function Action pfInitArenas Create arenas for shared memory and semaphores pfSharedArenaSize Specify the size of a shared memory arena pfGetSharedArena Get the shared memory arena pointer pfGetSemaArena Get the shared semaphore lock arena pointer pfMalloc Allocate from an arena or the heap pfFree Release memory allocated with pfMalloc Allocating Memory With pfMalloc pfMalloc can allocate memory either from the heap or from a shared memory arena Multiple processes can access memory allocated from a shared memory arena whereas memory allocated from the heap is visible only to the allocating process Pass a shared memory arena pointer to pfMalloc to allocate memory from the given arena pfGetSharedArena returns the pointer for the arena allocated by pfInitArenas or NULL if the given memory was allocated from
400. ke New York For information call 212 587 4148 504 Figure A 7 Simulated conference room The image in Figure A 7 was created by Advanced Graphics Applications 505 Appendix A Image Gallery Figure A 8 Parliament stairway The image in Figure A 8 was created by A J Diamond Donald Schmitt and Company 506 Figure A 9 Unity Temple interior The image in Figure A 9 was created by Lightscape Technologies Inc The database that the image illustrates is a model of the Unity Church and community house project designed by Frank Lloyd Wright in 1906 This database is part of the IRIS Performer software distribution 507 Glossary alias An alternate extension for a file type as processed by the pfdLoadFile utility For example VRML wrl files are in a sense an alias for Open Inventor iv files since the Open Inventor loader can read VRML files as well Once the alias is established files with alternate extensions will be loaded by the designated loader application buffer The main and usually only buffer of libpf data structures such as the nodes in the scene graph Alternate buffers may be created and data can be constructed in these new buffers from parallel processes to support high performance asynchronous database paging during real time simulation arena An area allocation area from which shared memory is allocated Usually the arena is the default one created by pfInit
401. l scenes to account for polygon size and position as well as for pipeline efficiency Specific Guidelines for Optimizing Performance Process Pipeline Tuning Tips These simple tips will help you optimize your IRIS Performer process pipeline Use pfMultiprocess to set the appropriate process model for the current machine You usually shouldn t specify more processes with pfMultiprocess than there are CPUs on the system The default multiprocess mode PFMP_DEFAULT attempts an optimal configuration for the number of unrestricted CPUs However if there are fewer processors than significant tasks consider APP CULL DRAW ISECT DBASE you will want experiment with the different two process models to find the one that will yield the best overall frame rate Use of pfDrawChanStats described in Chapter 12 Statistics will greatly help with this task Put only latency critical tasks between the pfSync and pfFrame calls For example put latency critical updates like changes to the viewpoint after pfSync but before pfFrame Put time consuming tasks such as intersection tests and system dynamics after pfFrame You will also want to refer to the IRIX REACT documentation for setting up a real time system For maximum performance use the IRIS Performer utilities in libpfutil for setting non degrading priorities and isolating CPUs pfuPrioritizeProcs pfuLockDownProc pfuLockDownApp pfuLockDownCull p
402. l be used for subsequent renderings until the pfGeoSet compiled mode flag is explicitly reset Once a pfGeoSet is compiled any changes to its data arrays by the pfMorph node or other means will not be effective until the compiled mode flag is cleared complex pixels Pixels for which several different geometric primitives contribute to the pixel s assigned color value Such pixels are rare in typical scenes and only exist at edges of polygons unless multisample blending is in use When this blending mode is used then all pixels rendered as neither fully opaque nor fully transparent are complex pixels critically damped A closed loop control system notion where the feedback transfer function is just right not so slow that the system goes out of range before correction is applied and not so fast that overcorrection causes rapid swings or variation This should be the goal of any user specified stress management function cull See culling cull volume visualization The visual display of the culling volume usually the same as the viewing frustum to which the scene is culled before rendering Normally the projected culling volume fills the display area By rendering with a larger field of view or from a eye point that differs from the origin of the frustum 513 Glossary 514 the tightness of culling can be determined for database tuning The culling volume itself is often drawn in wireframe culling Discarding databas
403. l group Typical shared attributes are field of view view specification near and far clipping distances the scene to be drawn stress parameters level of detail parameters the earth sky model and swapbuffer timing 511 Glossary 512 children IRIS Performer s hierarchical scene graph of pfNodes has internal nodes derived from the pfGroup class and each node attached below a pfGroup type node is known as a child of that node The complete list of child nodes are collectively termed the children of that node class hierarchy The provenance through which IRIS Performer classes are defined This class hierarchy defines the data elements and member functions of these data types through the notion of class inheritance as described below class inheritance Class inheritance describes the process of defining one object as a special version of another For example a pfSwitch node is a special version of a pfGroup node in that it has control information about which children are active for drawing or intersection In all other respects a pfSwitch has the same capabilities as a pfGroup and the Performer API supports this notion directly in both the C and C API by allowing a pfSwitch node to be used wherever a pfGroup is called for in a function argument This same flexibility is supported for all derived types clipped Geometry is said to be clipped when some or all of its geometric extent crosses one or more clipping planes
404. l return NULL in other processes This effectively precludes the creation of subclasses of IRIS Performer objects after pfConfig Virtual Address Spaces and Virtual Functions When using virtual functions it s very important that the object code reside at the same address in all processes Normally this is not an issue since the object code for all IRIS Performer classes is loaded whether statically linked or loaded as dynamic shared objects DSOs before pfConfig is called to fork off processes For user defined C classes with virtual functions it s important that the object code reside at the same virtual address space in all processes that access them For this reason the DSOs for any user defined classes should be loaded before pfConfig regardless of whether they use the pfType system or not Data Members and Shared Memory Non static Member Data The default operator new for objects derived from pfObject causes all instances to be created in shared memory so that objects will be visible to other related processes that need to see them 494 Multiprocessing and Shared Memory m Advanced Static Member Data Classes having static data members that may change value and need to be visible from all processes should allocate shared memory for the data e g pfMalloc or new pfMemory and set the static data member to point to this memory before pfConfig as shown in the following example Example 14 5 Changeable S
405. le 9 8 Object Tokens in the SGO Format Symbol Value Meaning OBJ_QUADLIST 1 Independent quadrilaterals OBJ_TRILIST 2 Independent triangles OBJ_TRIMESH 3 Triangle mesh OBJ_END 4 End of data token The next word following any of the three object types is the number of 4 byte words of data for that object The format of this data varies depending on the object type For quadrilateral list OBJ QUADLIST and triangle list OBJ_TRILIST objects there are nine words of floating point data for each vertex as follows 1 Three words that specify the components of the normal vector at the vertex 2 Three words that specify the red green and blue color components scaled to the range 0 0 to 1 0 3 Three words that specify the X Y and Z coordinates of the vertex itself 305 Chapter 9 Importing Databases 306 In quadrilateral lists vertices are in groups of four so there are 4 X 9 36 words of data for each quadrilateral In triangle lists vertices are in groups of three for 3 X 9 27 words per triangle The triangle mesh OBJ_TRIMESH is the most complicated of the three object data types Triangle mesh data consists of a set of vertices followed by a set of mesh control commands Triangle mesh data has the following format 1 Along word that contains the number of words in the complete triangle mesh data packet 2 Along word that contains the number of floating point words required by the vertex data at
406. le programs Example 5 14 Inheritance demonstration program inherit c transform inheritanc xampl E include lt math h gt include lt Performer pf h gt include lt Performer pfdu h gt int main int argc char argv pfPipe pipe pfPipeWindow pw pfScene scene pfChannel chan pfCoord view float lt lt Ssp G pfNode modell model2 pfDCS nodel node2 pfDCS dcsl dcs2 dcs3 dcs4 pfSphere sphere char filel file2 Sample Program choose default objects of none specified filel argc gt 1 argv 1 blob nff file2 argc gt 1 argv 1l torus nff Initialize Performer pfInit pfFilePath data ef data Mth ce ate data WS alah oe aba ME ere are e chs si data usr share Performer data Single thread for simplicity pfMultiprocess PFMP_DEFAULT Load all loader DSO s before pfConfig forks pfdInitConverter filel pfdInitConverter file2 Configure pfConfig Load the files if modell pfdLoadFile filel NULL pfExit exit 1 if model2 pfdLoadFile file2 NULL pfExit exit 1 scale models to unit size nodel pfNewDCS pfAddChild nodel modell pfGetNodeBSphere modell amp sphere if sphere radius gt 0 0f pfDCSScale nodel 1 0f sphere radius 147 Chapter 5 Nodes and Node Types
407. libpfobj so Any number of file loaders may be accessed through the single pfdLoadFile function which uses special dynamic shared object features to locate and use the proper loader corresponding to the extension of the file being loaded Figure 2 1 illustrates the relationships between the IRIS Performer libraries and the IRIS system software All IRIS Performer features are provided as a layer above the IRIX operating system and the graphics library IRIS Performer doesn t isolate application programs from IRIX or the graphics library however Even when using IRIS Performer to its fullest extent applications have free access to all system layers including not only libpf libpr and the libpfdu loader and builder libraries but the graphics library and IRIX as well What Is IRIS Performer Figure 2 1 IRIS Performer Library Hierarchy Developers are free to choose which of the libraries best suits their needs You may want to build your own toolkits on top of libpr but you still link with libpf you just don t use any libpf features or you can take advantage of the visual simulation development environment that libpf provides IRIS Performer defines a run time only database through its programming interface it doesn t define an archival database or file format Applications import their databases into IRIS Performer run time structures You can either write your own routines to do this or use one of the many database loader
408. lications can use the pfLayer node to include decals within a scene graph Frontface Backface pfCullFace controls which side of a polygon if any is discarded in the Geometry Pipeline Polygons are either front facing or back facing A front facing polygon is described by a counterclockwise order of vertices in screen coordinates and a back facing one has a clockwise order pfCullFace has four possible arguments PFCF_OFF Disable face orientation culling PFCF_BACK Cull back facing polygons PFCF_FRONT Cull front facing polygons PFCF_BOTH Cull both front and back facing polygons In particular backface culling is highly recommended since it offers a significant performance advantage for databases where polygons are never be seen from both sides databases of solid objects or with constrained eyepoints 339 Chapter 10 libpr Basics 340 Antialiasing pfAntialias is used to turn the antialiasing mode of the hardware on or off Currently antialiasing is implemented differently by each different graphics system Antialiasing can produce artifacts as a result of the way IRIS Performer and the active hardware platform implement the feature See the reference page for pfAntialias for implementation details Rendering Values Some modes may also have associated values These values are set through pfGStateVal Table 10 8 lists and describes the value tokens Table 10 8 pfGeoState Value Tokens Token Nam
409. lines as supported on Onyx RealityEngine systems you can create a pfPipe and pfChannel pair for each hardware pipeline The following code fragment illustrates a two channel two pipeline configuration leftPipe pfGetPipe 0 leftView pfNewChan leftPipe rightPipe pfGetPipe 1 rightView pfNewChan rightPipe Using Channels This configuration forms the basis for a high performance stereo display system since there is a hardware pipeline dedicated to each eye and rendering occurs in parallel The two channel stereo view application described in this example and the inset view application described in the previous example can be combined to provide stereo views for a driving simulator with an inset rear view mirror The correct management of each eye s viewpoint and the mirror reflection helps provide a convincing sense of physical presence within the vehicle The third common multiple channel situation involves support for multiple video outputs per pipeline To do this first associate each pipeline with a set of nonoverlapping channels one for each desired view Next use one of the following video splitting methods e Use the Multi Channel Option available from Silicon Graphics for systems such as the Onyx RealityEngine where you can create up to six independent video outputs from a single Graphics Pipeline with each video output corresponding to one of the tiled channels e Connect multiple video moni
410. list flag For example if the first polygon were a quad the connectivity array might start with 1 2 3 4 to define a polygon that connects the first four vertices in order 275 Chapter 9 Importing Databases 276 The following BYU format file defines two adjoining quads 262 0 he 22 000100 0 10 10 0 0 10 0 10 10 10 0 10 10 123 4 435 6 pfdLoadFile uses the function pfdLoadFile_byu to import data from byu format files into IRIS Performer run time data structures Designer s Workbench DWB Format The binary DWB format is used for input and output by the Designer s Workbench EasyT and EasyScene database modeling tools produced by Coryphaeus Software DWB is an advanced database format that directly represents many of IRIS Performer s attribute and hierarchical scene graph concepts An importer for this format named pfdLoadFile_dwb has been provided by Coryphaeus Software for your use The loader code and its associated documentation are in the usr share Performer src libflibpfdb libpfdwb directory The image in Figure 9 2 shows a model of the Soma Cube puzzle invented by Piet Hein The model was created using Designer s Workbench Each of the pieces is stored as an individual DWB format file Do you see how to form the 3 x 3 cube at the lower left from the seven individual pieces Description of Supported Formats Figure 9 2 Soma Cube Puzzle in DWB Form pfdLoadFile uses th
411. ller and thus can be rendered with less detail The IRIS Performer pfLOD node and the associated pfLODState implement this scheme libpf One of IRIS Performer s two core libraries libpf manages multiprocessing and scene graph traversals Built on top of libpr Multiple copies of libpf objects are automatically maintained so that the APP CULL and ISECT stages of the processing pipeline do not collide libpfdu IRIS Performer s database utilities library Layered on top of libpf and libpr Includes functions for building and optimizing geometry before putting it into a scene graph libpfutil IRIS Performer s general utility library which is distributed in source form for both usage and information libpr One of IRIS Performer s two core libraries libpr manages graphics state and rendering while also providing a number of math and shared memory utility functions Provides the foundation for libpf All processes share the same copy of libpr objects libpr classes The low level structured data types of libpr These objects with the exception of pfCycleBuffers lack the special multibuffered multiprocess data exclusion support that libpf objects provide light point A point of light such as a star or a runway light Accurate display of light points requires that they attenuate and fog differently than other geometry see punch through In flight simulation light points often have additional parameters concerning angular
412. loc 6 sizeof ushort arena 5 2 nindex 2 1 nindex 5 ef pfMalloc 4 sizeof pfVec2 arena ort pfMalloc 24 sizeof ushort arena pfGeoSet out of the same arena gset pfNewGSet arena set the coordinate normal and color arrays and their corresponding index arrays libpr Sample Code aA pfGSetAttr gset PFGS_COORD3 PFGS_PER_VERTEX verts vindex pfGSetAttr gset PFGS_NORMAL3 PFGS_PER_PRIM norms nindex pfGSetAttr gset PFGS_TEXCOORD2 PFGS_PER_VERTEX tcoords tindex pfGSetPrimType gset PFGS_QUADS pfGSetNumPrims gset 6 el wm create a geostate from the arena enabl texturing in case that s not the default and set the geostate for this geoset Xf gst pfNewGState arena pfGStateMode gst PFSTATE_ENTEXTURE 1 pfGSetGState gset gst create a new texture from shared memory load a texture file and add texture to geostat Ee tex pfNewTex arena pfLoadTexFile tex brick rgba pfGStateAttr gst PFSTATE_TEXTURE tex Create a new textur nvironment from the arena tenv pfNewTEnv arena Decal the texture since the geoset has no color to modulate pfTEnvMode tenv PFTE_DECAL set the textur nvironment for this pfGeoState pfGStateAttr gst PFSTATE_TEXENV tenv
413. lygon Delete local polygon struct pfdDelGeom polygon 261 Chapter 9 Importing Databases 262 Close File fclose iimFile Optimize IRIS Performer scene graph via use of pfFlatten pfdCleanTree etc OptimizeGraph root return pfNode root Now for at the heart of the file loader lies the ParseIIMFile function The specifics of parsing a file are completely dependent on the format so the parsing will be left as an exercise to the reader However the following code fragments should show a framework for what goes into integrating the parser with the pfdBuilder framework for geometry and graphics state data conversion Note that several possible graphics state inheritance models might be used in external formats and that the pfdBuilder is designed to support all of them The default pfdBuilder state inheritance is that of immediate mode graphics state Immediate mode state is specified through calls to pfdBldrStateMode pfdBldrStateAttr and pfdBldrStateVal There also exists a pfdBuilder state stack for hierarchical state application to geometry This is accomplished through the use of pfdPushBldrState and pfdPopBldrState in conjuncture with the normal use of the immediate mode pfdBuilder state API Lastly there is a pfdBuilder named state list that can be used to define a number of named materials or named state definitions that can then be recalled in one A
414. m parts of an animated character such as facial expressions Generalized Morphing Simple pair wise morphing is not sufficient to give animated characters life like emotional expressions and behavior You need the ability to model multiple expressions in an orthogonal manner and then combine them with arbitrary weighting factors during real time simulation Survey of Visual Simulation Techniques One current approach to human facial animation is to build a geometric model of an expressionless face and then to distort this neutral model into an independent target for each desired expression Examples include faces with frowns and smiles faces with eye gestures and faces with eyebrow movement Subtracting the neutral face from the smile face gives a set of smile displacement vectors and increases efficiency by allowing removal of null displacements Completing this process for each of the other gestures yields the input needed by a real time system a base or neutral model and a collection of displacement vector sets In actual use you would process the data in a straightforward manner You would specify the weights of each source model or corresponding displacement vector set before each frame is begun For example a particular setting might be 62 grin and 87 arched eyebrows for a clownish physiognomy The algorithmic implication is simply a weighted linear combination of the indicated vectors with the base model These pro
415. m 0 to 1 By default a pfChannel viewport covers the entire window Suppose that you want to establish a viewport that is one quarter of the size of the window located in the lower left corner of the window Use pfChanViewport chan 0 0 0 25 0 0 0 25 to set up the one quarter window viewport for the channel chan You can then set up other channels to render to the other three quarters of the window For example you can use four channels to create a four way view for an architectural or CAD application See Using Multiple Channels on page 100 to learn more about multiple channels Setting Up a Viewing Frustum A viewing frustum is a truncated pyramid that defines a viewing volume Everything outside this volume is clipped while everything inside is projected onto the viewing plane for display A frustum is defined by e field of view FOV in the horizontal and vertical dimensions e near and far clipping planes A viewing frustum is created by the intersections of the near and far clipping planes with the top bottom left and right sides of the infinite viewing volume formed by the FOV and aspect ratio settings The aspect ratio is the ratio of the vertical and horizontal dimensions of the FOV 93 Chapter 4 Setting Up the Display Environment 94 Figure 4 3 shows the parameters that define a symmetric viewing frustum To establish asymmetric frusta refer to the pfChannel 3pf or pfFrustum 3pf reference pages for fu
416. mask which you set with pfChanTravMask By default the masks are all 1s or Oxffffffff Controlling and Customizing Traversals Before testing a node for visibility the cull traversal ANDs the two masks together If the result is zero the cull prunes the node If the result is nonzero the cull proceeds normally Mask testing occurs before all visibility testing and function callbacks Masks allow you to draw different subgraphs of the scene on different channels to turn portions of the scene graph on and off or to ignore hidden portions of the scene graph while drawing but make them active during intersection testing pfNode Cull and Draw Callbacks One of the primary mechanisms for extending IRIS Performer is through the use of function callbacks which can be specified on a per node basis IRIS Performer allows separate cull and draw callbacks which are invoked both before and after node processing Node callbacks are set with pfNodeTravFuncs Cull callbacks can direct the cull traversal while draw callbacks are added to the display list and later executed in the draw traversal for custom rendering There are pre cull and pre draw callbacks invoked before a node is processed and post cull and post draw callbacks invoked after the node is processed The cull callbacks return a value indicating how the cull traversal should proceed as shown in Table 6 2 Table 6 2 Cull Callback Return Values Value Action PFTRAV_
417. me consuming operations such as intersection inquiries and simulator dynamics computations that are performed in the main simulation loop should go after pfFrame but before pfSync If these calculations are done after pfSync but before pfFrame the calculations can delay the start of the cull process and thereby reduce the time available for the cull traversal on multiprocessor systems This chapter doesn t specifically discuss performance tuning see Chapter 13 Performance Tuning and Debugging for detailed information on that topic but every IRIS Performer based application should be written with performance in mind Speed is not something that you can easily build into an application as a last minute addendum it s something that you need to consider as you structure your database as you decide what needs to happen in your main loop and so on during the design of your program rather than after debugging it Once you understand the basics of building a visual simulation application you should go on to learn how to enhance performance by reading Chapter 13 It might be useful to skim Chapter 3 before reading any further so that as you read more about the details of building an application with IRIS Performer you ll have performance issues in mind from the start Compiling and Linking IRIS Performer Applications Compiling and Linking IRIS Performer Applications This section describes how to compile and link IRIS Perf
418. mebuffer configuration such as single buffered stereo etc You can use utilities in libpr to help you with this task or create your own framebuffer configuration structure with X utilities or even create the window yourself and apply it to the pfWindow pfOpenWin will respect any specified framebuffer configuration Additionally pfOpenWin uses any window or graphics context that is assigned to it and only creates what is undefined 367 Chapter 10 libpr Basics 368 pfWinFBConfigAttrs can be used to specify an array of framebuffer attribute tokens listed in Table 10 20 The tokens are exactly like the OpenGL X tokens and the same attribute list can be used for all window types pure IRIS GL mixed model IRIS GL and OpenGL X windows Note that if an attribute array is specified the tokens modify configuration with no attributes set not the default IRIS Performer framebuffer configuration Table 10 20 pfWinFBConfigAttrs Tokens PFFB_ Token Value Description BUFFER_SIZE integer gt 0 The size of the color index buffer LEVEL integer gt 0 The color plane level normal color planes have level 0 overlay color planes have level gt 0 underlay color planes have level lt 0 There may be only one or no levels for overlay and underlay color planes on some graphics hardware configurations RGBA Boolean Use RGBA color planes instead of color true if index present DOUBLEBUFFER Boolean Use double buffered color buffers
419. mited It is possible for rendering calls issued in the previous section to fill up the graphics FIFO and have calls issued on this section have to wait while the graphics pipeline processes the commands and FIFO drains making the time look longer than expected The time spent waiting for the graphics pipeline to finish drawing the current frame draw the channel statistics for all channels and swap color buffers This line may look quite long as the color buffers can only be swapped on a vertical retrace boundary Thus this pale dotted line will always reach to the start of the next field Below the stage timing lines the average time for each stage in milliseconds is shown Note that the time given for the draw stage is the same as the time shown for the draw stage on the status line above the statistics box 429 Chapter 12 Statistics 430 Load and Stress The lower portion of the channel statistics diagram shows the recent history of graphics load and stress management The load measure is based on the amount of time taken to draw previous frames in the channel relative to the specified goal frame time A wavy red horizontal line is drawn to show the last three seconds of graphics load A pair of white horizontal lines represent the upper and lower bounds of graphics load for invoking stress management Thus when the red line wanders outside the boundaries set by the white lines stress management is invoked Stress mana
420. modular relationship of the differences in the least significant bits of interpolated depth between the polygons The libpr pfDecal function and libpf pfLayer node exist to handle the drawing of coplanar geometry without flimmering floating phase The style of frame overload management where the next frame after an overloaded frame is allowed to start at any vertical retrace boundary rather than being forced to wait for a specific boundary as in the LOCKED phase frame The term frame is used to mean image in most IRIS Performer contexts The image being rendered by the hardware is drawn into a frame buffer which is simply an image memory This image when delivered via video signals to a monitor or projector exists as one or two video fields In the one field case also known as non interlaced each row of the image is read from the frame buffer and generated as video in sequential order In the interlaced method the first field of display comprises alternate lines one field for the odd lines and one field for the even lines In this mode a frame consists of two fields as the norm for NTSC broadcast video Also the frame is the unit of work in Performer the main loop in any Performer application consists of calls to pfFrame frame accurate Ina pipelined multiprocessing model at any particular time the different stages of the pipeline is working on different frames Data in the pipeline is called frame accurate when a
421. mplest type of animation sequence is known as a geometry movie It is a sequence of exclusive objects that are selected for display based on elapsed time from a trigger event Advancement is tied to frames rather than time or is based on specific events within the database For further information on animation see pfSequence Nodes in Chapter 5 Antialiasing Antialiased image generation can have a significant effect on image quality in visual simulation The difference though subtle in some cases has very significant effects on the sense of reality and the suitability of simulators for training Military simulators often center on the goal of detecting and recognizing small objects on the horizon Aliased graphics systems produce a sparkle or twinkle effect when drawing small objects This artifact is unacceptable in these training applications since the student will come to subconsciously expect such effects to announce the arrival of an opponent and this unfulfilled expectation can prove fatal The idea of antialiasing is for image pixels to represent an average or other convolution of the image fragments within a pixel s area rather than simply be a sample taken at the pixel s center This idea is easily stated but difficult to implement while maintaining high performance The RealityEngine antialiasing approach is termed multisampling In this system each pixel is considered to be composed of multiple subpixels Mul
422. n process as soon as an OBJ_TRIMESH data type token is encountered If you use SGO format files containing triangle meshes you ll need to extend the conversion support to include the triangle mesh data type USNA Simple Polygon File Format The spf format is used at the United States Naval Academy as a simple polygon file format for geometric data The loader was developed based on the description in the book Mathematical Elements for Computer Graphics The IRIS Performer spf loader is in the usr share Performer src libflibpfdb libpfspf directory The following spf format file is defined in that book polygon with a hole 14 2 4 4 4 26 20 26 28 18 28 4 21 4 21 8 10 8 10 4 10 12 10 20 17720 21 16 21 12 Iele 2 Sr 47 57 05 Ve BPO 5 10 11 12 13 14 If you look at this file in Perfly you will see that the hole is not cut out of the letter A as might be desired Such computational geometry computations are not considered the province of simple database loaders 307 Chapter 9 Importing Databases 308 pfdLoadFile uses the function pfdLoadFile_spf to load SPF format files into IRIS Performer run time data structures Sierpinski Sponge Loader The Sierpinski Sponge a k a Menger Sponge loader is not based on a data format but rather is a procedural data generator The loader interprets the portion of the user provided file name before the period and extension as an inte
423. n the current depth of the stack Premultiply the TOS by a translation Postmultiply the TOS by a translation Premultiply thee TOS by a rotation Postmultiply the TOS by a rotation Premultiply the TOS by a scale factor Postmultiply the TOS by a scale factor 407 Chapter 11 Math Routines Creating and Transforming Volumes 408 libpr provides a number of volume primitives including sphere box cylinder half space plane and frustum libpf uses the frustum primitive for a view frustum and uses other volume primitives for bounding volumes e Nodes use bounding spheres e pfGeoSets use bounding boxes e Segments use bounding cylinders Defining a Volume This section describes how to define geometric volumes Spheres Spheres are defined by a center and a radius as shown by the pfSphere structure s definition typedef struct pfVec3 center float radius pfSphere A point p is in the sphere with center c and radius rif p cl lt r Axially Aligned Boxes An axially aligned box is defined by its two corners with the smallest and largest values for each coordinate Its edges are parallel to the X Y and Z axes It s represented by the pfBox data structure typedef struct pfVec3 min pfVec3 max pfBox A point x y z is in the box if min lt x lt max miny lt y lt maxy and min lt zZ lt maxz Creating and Transforming Volumes Cylinders A cylinder is defined by its
424. nd Functions Provided by User Subclasses Class Data or Function Function static void init Initialize the new class static pflype getClassType Returns the pfType of the new class static pflype classType Stores the pfType of the new class constructor Sets the pfType for each instance The init member function should initialize any data structures that are related to the class as a whole as opposed to any particular instance The most important of these is the entry of the class into the type system For example the Rotor class defined in the Open Inventor loader see Rotor h and Rotor C in usr share Performer src lib libpfdb libpfiv is a subclass of pfDCS It s initialization function merely enters the class into the type system Example 14 3 Class Definition for a Subclass of pfDCS public Rotor public pfDCS static void init static pfType getClassType return classType static pfType classType pfType Rotor classType NULL Rotor Rotor setType classType set the type of this instance void Rotor init 491 Chapter 14 Programming with C if classType NULL pfDCS init classType new pfType pfDCS getClassType Rotor As described in the section below the initialization function Rotor init should be called before pfConfig Defining Virtual Functions Below is the example of the Rotor class which specifies the traversal
425. nd matrix transformations Some of the libpr statistics commands such as pfEnableStatsHw PFSTATSHW_ENGFXPIPE_FILL require an active graphics context and thus should only be called from the draw process However these commands are usually never necessary in a libpf application 435 Chapter 12 Statistics 436 because the pfFrameStats operation will handle these commands automatically Statistics Class Structures The pfFrameStats structure and the pfStats structure are both inherited from the pfObject structure Thus you can use the pfObject routines pfCopy pfPrint pfDelete pfUserData pfGetType and so on with pfStats and pfFrameStats structures However some pfObject routines will not support all of the semantics of a pfStats or pfFrameStats structure so some pfStats versions of a few of these routines take extra arguments These routines will have a pfFrameStats version as well In particular pfCopyStats and pfCopyFStats should be used to copy pfStats and pfFrameStats structures respectively Routines that have FStats in their names rather than just Stats expect to be passed a full pfFrameStats structure rather than a pfStats structure The pfFrameStats API includes additional routines beyond pfStats for supporting libpf statistics For example pfDrawFStats to display statistics in a channel and pfFStatsCountNode to accumulate the static database statistics for the scene graph rooted at th
426. nd place them in a database hierarchy See Geometry in Chapter 10 for information on constructing pfGeoSets and Scene Graph Hierarchy in Chapter 6 for information on creating a scene graph Create a new scene for the channel to draw scene pfNewScene 59 Chapter 3 Building a Visual Simulation Application 60 10 11 12 Add the root of the database that you loaded or created in step 6 to the scene pfAddChild scene root Initialize a graphics rendering pipeline p pfGetPipe 0 pw pfNewPWin p pfPWinType pw PFPWIN_TYPE_X pfPWinName pw IRIS Performer pfPWinOriginSize pw 0 0 500 500 Open and configure the graphics window pfOpenPWin pw This sets up a callback to open a graphics library window sized and positioned as specified in OpenPipeWin Specify the frame rate and the synchronization method Because neither a frame rate nor a synchronization method is specified in simple c the application free runs without frame rate control which is the default See Frame Rate and Synchronization on page 63 and Chapter 7 Frame and Load Control for more information on controlling frame rates Create a channel on the specified pipe chan pfNewChan p A channel is a viewport into a pipe Because simple c doesn t configure any screen dimensions for the channel it renders to the full window of the pipe Configure the channel
427. nd third ranges LOD 2 is drawn This range bracketing continues until the final range is passed at which point nothing is drawn The pfLOD node s switch range list contains one more entry than the number of child nodes to allow for this range bracketing IRIS Performer provides the ability to specify a blend zone for each switch between LOD models Such that pfLOD nodes now also hold a list of these transition distances over which Performer should blend between neighboring LODs These blend zones will be discussed in more detail in Level of Detail Transition Blending on page 207 Level of Detail States IRIS Performer 2 0 supports a new concept along with the aforementioned standard LOD node which contains switch ranges and transition zones This new concept is one of an LOD state the pfLODState A pfLODState is an essence a way of creating classes or priorities among LODs A pfLODstate contains eight parameters used to modify four different ways in which Performer calculates LOD switch ranges and LOD transition distances LOD states contain the following parameters e Scale for LODs switch Ranges e Offset for LODs switch Ranges e Scale for the effect of Stress of switch Ranges e Offset for the effect of Stress on switch Ranges e Scale for the transition distances per LOD switch e Offset for the transition distances per LOD switch e Scale for the effect of Stress on transition distances e Offset for the effect of S
428. nding element of v2 FALSE otherwise PFALMOST_EQUAL_VEC3 A pfMatrix is a 4x4 array of floating point numbers that is used primarily to specify a transformation in homogeneous coordinates x y z w Table 11 2 describes the IRIS Performer mathematical operations that act on matrices Table 11 2 Routines for 4x4 Matrices Routine Effect pfMakelIdentMat d D I pfMakeVecRotVecMat d v1 v2 D M such that Vo vM Vy Vo normalized pfMakeQuatMat d q D M where M is the rotation of the quaternion q pfMakeRotMat d deg x y z D M where M rotates by deg around x y Z pfMakeEulerMat d h p r D RPH where R P and H are the transforms for roll pitch and heading Macro Equivalent PFMAKE_IDENT_MAT none none none none 399 Chapter 11 Math Routines 400 Table 11 2 continued Routines for 4x4 Matrices Routine Effect Macro Equivalent pfMakeTransMat d x y z pfMakeScaleMat d x y z pfMakeCoordMat d c pfGetOrthoMatQuat s q pfGetOrthoMatCoord s d pfSetMatRow d r x y z w pfGetMatRow m r x y z w pfSetMatCol d c x y z w pfGetMatCol m c x y z w pfSetMatRowVec3 d r v pfGetMatRowVec3 m r d pfSetMatColVec3 d c v pfGetMatColVec3 m c d D M where M translates by x y z D M where M scales by x y z D M where M rotates by h p r and translates by x y z with h p 1
429. nding the data to the pipeline the current pfDispList captures the pfDrawGSet command The given pfGeoSet is then drawn along with the rest of the pfDispList with the pfDrawDList command When the PFGS_COMPILE_GL mode of a pfGeoSet is not active pfGSetDrawMode pfDrawGSet uses rendering loops tuned for each primitive type and attribute binding combination to reduce CPU overhead in transferring the geometry data to the hardware pipeline Otherwise pfDrawGSet sends a special compiled data structure Table 10 1 lists other operations that you can perform on pfGeoSets pfCopy does a shallow copy copying the source pfGeoSet s attribute arrays by reference and incrementing their reference counts pfDelete frees the memory of a pfGeoSet and its attribute arrays if those arrays were allocated with pfMalloc and provided their reference counts reach zero pfPrint is strictly a debugging utility and will print a pfGeoSet s contents to a specified destination pfGSetIsectSegs allows intersection testing of line segments against the geometry in a pfGeoSet see Intersecting With pfGeoSets in Chapter 11 for more information on that function 3D Text In addition to the pfGeoSet libpr offers two other primitives which together are useful for rendering a specific type of geometry three dimensional characters See Chapter 5 Nodes and Node Types and the description for pfText nodes for an example of how to set up
430. nding volume from the bounding boxes of its pfGeoSets pfNodeBSphere geode NULL PFBOUND_DYNAMIC Node Types Node Types This section describes the node types and the functions for working with each node type pfScene Nodes A pfScene is a root node that is the parent of a visual database Use pfNewScene to create a new scene node Before the scene can be drawn you must call pfChanScene channel scene to attach it to a pfChannel Any nodes that are within the graph that is parented by a pfScene are culled and drawn once the pfScene is attached to a pfChannel Because pfScene is a group it uses pfGroup routines however a pfScene cannot be the child of any other node The following statement adds a pfGroup to a scene pfAddChild scene root In the simplest case the pfScene is the only node you need to add Once you have a pfPipe pfChannel and pfScene you have all the necessary elements for generating graphics using IRIS Performer pfScene Default Rendering State pfScene nodes may specify a global pfGeoState that all other pfGeoStates in nodes below the pfScene will inherit from Specification of this scene pfGeoState is done via the function pfSceneGState This functionality allows for the subtle optimization of pushing the most frequently used pfGeoState attributes for a particular scene graph into a global state and having the individual states inherit these attributes rather than specify them This can sa
431. ndow pfSelectPWin pwin call the main IRIS Performer drawing function pfDraw Notice that in Example 4 3 although the pfPipeWindow is doublebuffered the front and back color buffers are never swapped This operation is done automatically after all channels on the parent pfPipe have completed their drawing for the given frame You may need to set additional window and graphics state to complete the initialization of your pfPipeWindow Calling pfOpenPWin from the application process does not give you the opportunity to do this However with pfPWinConfigFunc you can supply a window configuration callback function that will enable you to open and initialize your pfPipeWindow in the draw process A call to pfConfigPWin will trigger one call of the window configuration callback in the draw process upon the next call to pfFrame pfConfigPWin can be called at any time to trigger the calling of the current window configuration function in the draw process Example 4 4 demonstrates initializing a pfPipeWindow from a draw process callback It creates a special extra depth buffer and local light model for supporting IRIS GL shadows see the usr share Performer src pguide libpf C shadow c example Example 4 4 Custom initialization of pfPipeWindow state main pfPipe pipe 85 Chapter 4 Setting Up the Display Environment pfPipeWindow pwin pfiInit pfConfig Create pfPipeWindow for pfPipe
432. ndow will come up as a rubber bend for the user to place and stretch Framebuffer configuration The window will be doublebuffered RGBA with depth and stencil buffers allocated The size of these buffers will depend on the available resources of the current graphics hardware platform GLX and OpenGL X windows will also have multisample buffers allocated if they are available on current hardware platform Libpr state A pfState will be created and initialized with all modes disabled and no attributes set Graphics state The pfWindow will be in RGBA color mode with subpixel vertex positioning depth testing and viewport clipping enabled The Viewing projection will be a two dimensional one one orthographic mapping from eye coordinates to window coordinates with distances to near and far clipping planes 1 and 1 respectively The model matrix will be the current matrix and will be initialized to the identity matrix Typically pfWindows go through a bit more initialization than that of Example 10 7 The type of pfWindow type set with pfWinType is a bitmask that selects the window system interface and the type of rendering window The default window type is a normal graphics rendering window and is pure IRIS GL under IRIS GL operation and X under OpenGL operation Table 10 19 lists the possible selectors that can be OR ed together for specification of the window type Table 10 19 pfWinType Tokens PFWIN_TYPE_ Description Bitmask
433. ng concatenated onto the ones above it in the scene graph This allows chained articulations and complex modeling hierarchies The effects of state are propagated downward only not from left to right nor upward This means that only parents can affect their children siblings have no effect on each other nor on their parents This behavior results in an easy to understand hierarchy that is well suited for high performance traversals Graphics state such as textures and materials are not inherited by way of the scene graph but are encapsulated in leaf geometry nodes called pfGeode nodes which are described in the section Node Types in Chapter 5 Database Organization IRIS Performer uses the spatial organization of the database to increase the performance of certain operations such as drawing and intersections It is therefore recommended that you consider the spatial arrangement of your database What you might think of as a logical arrangement of items in the database may not match the spatial arrangement of those items in the visual environment which can reduce IRIS Performer s ability to optimize operations on the database See Organizing a Database for Efficient Culling on page 163 for more information about spatial organization in a visual database and the efficiency of database operations Application Traversal Application Traversal The application traversal is the first traversal that occurs during the processin
434. ng list xxxv making databases 36 malloc 474 See also memory pfMalloc masks intersection 181 417 materials 349 math functions 33 math routines 397 421 in lining 466 matrices 4by 4 399 affine 402 composition order 402 manipulating 352 stack functions 407 matrix routines transformations 399 matrix See transformation measuring performance 467 474 MEDIT format See formats Medit Productions Medit 252 Medit format 37 Medit modeler 15 member functions 481 overloaded 490 memory allocating 386 474 multiprocessing 226 shared See shared memory memory mapping for shared arena 387 Menger sponge 38 308 minification 465 MIP map interpolation functions 465 mixed model programming 79 mode changes 454 modelers AutoCAD 277 Designer s Workbench 276 EasyScene 276 EasyT 276 I3DM 311 543 Index Imagine 286 Kaleido 295 Model 293 ModelGen 280 MultiGen 280 models 28 58 Moller 400 aircar 286 morph attribute definition 521 morphing 26 244 characters 27 defined 521 terrain 26 Motif 91 motion models drive 4 flight 6 motion sickness See simulator sickness multibuffering 495 Multi Channel Option 103 MultiGen OpenFlight format 37 multiple channels 97 103 105 rendering 100 multiple hardware pipelines 74 multiple inheritance avoidance of 45 definition 521 multiple pipelines See pipelines multiprocessing display list generation
435. nine words per vertex 3 The data for each vertex consisting of nine floating point words representing normal color and coordinate data 4 A list of triangle mesh controls The triangle mesh controls each of which is one word in length are listed in Table 9 9 Table 9 9 Mesh Control Tokens in the SGO Format Symbol Value Meaning OP_BGNTMESH 1 Begin a triangle strip OP_SWAPTMESH 2 Exchange old vertices OP_ENDBGNTMESH 3 End then begin a strip OP_ENDTMESH 4 Terminate triangle mesh The triangle mesh controls are interpreted sequentially The first control must always be OP_BGNTMESH which initiates the mesh decoding logic After each mesh control is a word of type long integer that indicates how many vertex indices follow The vertex indices are in byte offsets so to access vertex n you must use the byte offset n X 9 X 4 See the graphics library reference books listed under Bibliography on page xxix for more information on triangle meshes particularly see the IRIS GL books if you re using IRIS GL for information on the swap triangle mesh concept Description of Supported Formats pfdLoadFile uses the function pfdLoadFile_sgo to load SGO format files into IRIS Performer run time data structures You can find the source code for the SGO format importer in the file pfsgo c This importer doesn t attempt to decode any triangle meshes present in input files instead it terminates the file conversio
436. ning Tips 453 Process Pipeline Tuning Tips 457 Database Concerns 461 Special Coding Tips 466 Performance Measurement Tools 467 Using pixie and prof to Measure Performance 467 Using gldebug and ogldebug to Observe Graphics Calls 468 Using glprof to Find Performance Bottlenecks 469 Guidelines for Debugging 474 Shared Memory 474 Use the Simplest Process Model 475 Avoid Floating Point Exceptions 475 xii 14 Notes on Tuning for RealityEngine Graphics 476 Multisampling 476 Transparency 476 Texturing 477 Other Tips 478 Programming with C 481 Overview 481 Class Taxonomy 482 Programming Basics 483 Header Files 483 Creating and Deleting IRIS Performer Objects 486 Invoking Methods on IRIS Performer Objects 487 Passing Vectors and Matrices to Other Libraries 487 Porting from C API to C API 488 Typedefed Arrays vs Structs 488 Interface Between C and C API Code 489 Subclassing pfObjects 490 Initialization and Type Definition 491 Defining Virtual Functions 492 Accessing Parent Class DataMembers 493 Multiprocessing and Shared Memory 493 Initializing Shared Memory 493 Data Members and Shared Memory 494 libpf Objects and Multiprocessing 495 Performance Hints 496 Image Gallery 499 Glossary 509 Index 531 xiii Examples Example 2 1 Example 2 2 Example 2 3 Example 2 4 Example 2 5 Example 3 1 Example 4 1 Example 4 2 Example 4 3 Example 4 4 Example 4 5 Example 4 6 Example 4 7 Example 4 8 Example 4 9
437. normally visible to the application since even for callbacks in the CULL and ISECT processes the application always works from the pointer to the copy used in the APP process in part so that objects can be identified by comparison of pointers However this difference would be visible if the virtual traversal functions for culling or intersection were overloaded These virtual functions should not be overloaded by the subclass since they will not have any effect when the CULL or ISECT stages are in separate processes Node callbacks specified with pfNodeTravFuncs should be used instead Subclassing will be vastly simplified and more flexible in a future release Constructor Overhead It s quite natural to frequently construct and destroy arrays of public structs such as pfVec3 on the stack Beware even though the constructors for these classes are empty it still requires a function call for each element of the array The same applies to classes such which contain arrays of structs e g pfSegSet contains an array of pfSegs Math Operators Assignment operators e g are significantly faster than their corresponding binary operators e g because the latter involves constructing a temporary object for the return value Appendix A Ima ge G allery This appendix contains images created using IRIS Performer and various scene models Appendix A Image Gallery This appendix contains views of some of the mo
438. not the pixel is rendered The reference value must be specified in the range 0 1 For example a pixel whose alpha value is 0 is not rendered if the alpha function is PPAF_GREATER and the alpha reference value is also 337 Chapter 10 libpr Basics 338 0 Note that rejecting pixels based alpha can be faster than using transparency alone A common technique for improving the performance of filling polygons is to set an alpha function that will reject pixels of low possibly non zero contribution Alpha function is typically used for see through textures like trees Decals On Z buffer based graphics hardware coplanar geometry can cause unwanted artifacts due to the finite numerical precision of the hardware which cannot accurately resolve which surface has visual priority This can result in flimmering a visual tearing or twinkling of the surfaces pfDecal is used to accurately draw coplanar geometry on IRIS platforms and it supports two implementation methods each with its advantages The stencil decaling method uses a hardware resource known as a stencil buffer and requires that a single stencil plane see IRIS GL stencil and OpenGL g1StencilOp man pages be available for IRIS Performer This method offers the highest image quality but requires that geometry be coplanar and rendered in a specific order which reduces opportunities for the performance advantage of sorting by graphics mode A potentially faster m
439. nput file Database Formats and IRIS Performer pfdLoadFile iv RY A iv NY format N a database N pfdLoadFile dwb N N 3 i Open 8 N N DWB nventor a N N N N format 8 N database X N RS i N Designer AN Workbench 7 X N SS Multigen FLT format database pfdLoadFile flt Scene created from various databases Figure 2 2 Relationship of IRIS Performer to Database Formats 39 Chapter 2 IRIS Performer Basics Graphics Libraries 40 IRIS Performer supports two graphics library APIs IRIS GL and OpenGL IRIS GL is supported as the primary graphics API for all systems prior to Indigo2 Impact such as the RealityEngine Silicon Graphics recommends using OpenGL on Impact and subsequent graphics hardware although OpenGL is supported on RealityEngine and many previous systems for application development and porting purposes The main difference between IRIS Performer s use of IRIS GL and of OpenGL is in how it handles windows and input there are relatively few circumstances in which your IRIS Performer based program will call graphics library routines directly this will usually only happen in draw callbacks see pfNode Cull and Draw Callbacks in Chapter 6 In fact most of the differences between IRIS GL and OpenGL are transparent to a developer using IRIS Performer the choice of which graphics library your application ends up using depends mostly on which libraries you link wit
440. ny active pfDispList A pfSprite s rotation mode is set by specifying the PFSPRITE_ROT token to pfSpriteMode In all modes the Y axis of the geometry is rotated to point to the eye position Rotation modes are listed below Table 10 17 pfSprite rotation modes PFSPRITE_ Rotation Token Rotation Characteristics AXIAL_ROT Geometry s Z axis is rotated about the axis specified with pfSpriteAxis POINT_ROT_EYE Geometry is rotated about the sprite position with the object coordinate Z axis constrained to the window coordinate Y axis i e geometry s Z axis stays upright POINT_ROT_WORLD Geometry is rotated about the sprite position with the object coordinate Z axis constrained to the sprite axis Rather than using the graphics hardware s matrix stack pfSprites transform small pfGeoSets on the CPU for improved performance However when a pfGeoSet contains a certain number of primitives it becomes more efficient to use the hardware matrix stack While this threshold is dependent on the CPU and graphics hardware used you may specify it with the PFSPRITE_MATRIX_THRESHOLD token to pfSpriteMode The corresponding value is the minimum vertex requirement for hardware matrix transformation Any pfGeoSet with fewer vertices will be transformed on the CPU If you want a pfSprite to affect non pfGeoSet geometry you should set the matrix threshold to zero so that the pfSprite will always use the matrix stack When using
441. ny others that might already be enabled Statistics Tokens There are five main types of statistics tokens Statistics class enable bitmasks used for selecting a set of classes to enable with pfStatsClass These bitmasks are also used when printing with pfPrint or copying with pfCopy and pfCopyStats as well as with the pfResetStats pfClearStats pfAverageStats and pfAccumulateStats routines and their pfFrameStats counterparts These tokens are of the form PFSTATS_EN and PFFSTATS_EN for pfStats and pfFrameStats class respectively The PFSTATS_ALL token will select all statistics classes and also all statistics buffers in the case of a pfFrameStats structure The token PFSTATS_EN_MASK selects all pfStats classes and the token PFFSTATS_EN_MASK selects all pfFrameStats statistics classes which includes all pfStats classes Value tokens used to specify how to set a value for a specified pfStats or pfFrameStats class enable or mode Value tokens include PFSTATS_ON PFSTATS_OFF and PFSTATS_DEFAULT Another value token PFSTATS_SET is used to specify that the entire class enable or mode bitmask should be set to the specified mask These tokens are used in conjunction with the class bitmasks and the class name tokens for pfStatsClass and pfStatsClassMode Class name tokens used to name a specific class For instance these tokens can be passed to pfStatsClassMode to set individual modes of a statistics class Cla
442. o define a minimally functional IRIS Performer scene graph See Chapter 5 for more details on libpf and IRIS Performer scene graphs and node types Defining Geometry and Graphics State for ibpr In order to input geometry and graphics into IRIS Performer it is important to have an understanding of how IRIS Performer s low level rendering objects work in libpr IRIS Performer s performance rendering library The main libpr rendering primitives are a pfGeoSet and a pfGeoState A Developing Custom Importers pfGeoSet is a collection of like geometric primitives that can all be rendered in exactly the same way in one large continuous chunk A pfGeoState is a complete definition of graphics mode settings for the rendering hardware and software It contains many attributes such as texture and material Given a pfGeoSet and a corresponding pfGeoState libpr can completely and efficiently render all of the geometry in the pfGeoSet For a more detailed description of pfGeoSets and pfGeoStates see Chapter 10 which goes into detail on all libpr primitives and how IRIS Performer will use them However realizing that IRIS Performer s structuring of geometry and graphics state is optimized for rendering speed and not for modelling ease or general conceptual partitioning IRIS Performer now contains a new mechanism for translating external graphics state and geometry into efficient libpr structures This new mechanism is the pfdBuilder that exists in
443. oadFile will call when it attempts to load a file with the extension iim extern pfNode pfdLoadFile_iim char fileName This function needs to perform several basic actions 1 2 3 4 Find and open the given file Reset the libpfdu pfdBuilder for input of new geometry and state Setup any pfdBuilder modes that the converter needs enabled Setup local data structures that can be used to communicate geometry and graphics state with the pfdBuilder Setup a libpf pfGroup which can hold all of the logical partitions of geometry in the file or hold a subordinate collection of nodes as a general scene graph if the format supports it Optionally set up a default state to use for geometry with unspecified graphics state Parse the file which entails e Filling in the local geometry and graphics state data structures e Passing them to the pfdBuilder as inputted from the file e Ask the pfdBuilder to build the data structures into IRIS Performer data structures when a logical partition of the file has ended e Attach the IRIS Performer node returned by the build to the higher level group which will hold the entire IRIS Performer representation of this file Note that this step becomes more complex if the format supports the notion of hierarchy only in that the appropriate libpf nodes must be created and attached to each other via pfAddChild to build the hierarchy In this case requests are made for the builder to buil
444. oaders is located in its own source directory the more complicated loaders may include further source subdirectories Users usually don t call these functions directly instead they call the libpfdu function pfdLoadFile which uses the extension part of the file name the part after the character to decide the format of the file and then automatically invokes the proper loader from libpfdb 37 Chapter 2 IRIS Performer Basics Many file loaders have been developed and most are available in source form as part of the IRIS Performer distribution Using these loaders as templates you can write custom loaders for whatever formats you require in your applications Database Formats and IRIS Performer 38 Although IRIS Performer doesn t define a file format it does provide sample source code for importing numerous other database formats into IRIS Performer s run time structures Figure 2 2 shows how databases are imported into IRIS Performer first a user creates a database with a modeling program then an IRIS Performer based application imports that database using one of the many importing routines IRIS Performer routines then manipulate and draw the database in real time Scene graphs can also be generated automatically by loaders with built in scene graph generation algorithms The sponge loader is an example of such automatic generation it builds a model of the Menger Sierpinski Sponge without requiring an i
445. oard 141 fNewBuffer 220 511 fNewCBuffer 391 fNewChan 92 fNewCtab 350 fNewDCS 127 fNewDList 355 fNewDPool 388 fNewESky 234 fNewFog 350 fNewFont 329 fNewFrust 409 fNewGeode 138 139 fNewGSet 320 fNewGState 361 fNewHlight 351 fNewLayer 131 fNewLight 348 fNewLModel 348 fNewLOD 130 fNewLPoint 132 236 fNewLSource 137 fNewMaterial 349 fNewMStack 407 fNewMtl 349 fNewPart 145 fNewPath 168 fNewPWin 79 88 fNewScene 125 fNewSCS 126 fNewSeq 128 fNewState 356 370 fNewString 332 fNewSwitch 127 fNewTex 343 fNewWin 364 fNodeBSphere 124 fNodelsectSegs 179 180 181 185 217 416 460 fNodeTravData 490 fNodeTravFuncs 171 490 493 496 fNodeTravMask 170 182 186 460 fNormalizeVec3 398 fNotify 386 392 fNotifyHandler 386 392 fNotifyLevel 392 458 475 pfOpenDList 355 pfOpenFile 391 pfOpenPWin 79 85 87 88 90 pfOpenScreen 366 374 pfOpenStats 438 pfOpenWin 364 367 370 372 373 pfOpenWSConnection 374 pfOrthoXformCyl 411 pfOrthoXformFrust 411 pfOrthoXformPlane 411 pfOrthoXformSphere 411 pfOverride 335 341 357 455 pfPartAttr 145 pfPassChanData 177 228 452 458 pfPassIsectData 228 pfPhase 193 195 pfPipeScreen 76 pfPlanelsectSeg 416 pfPopMatrix 172 353 ZGUUDTUVVVVUVUVUUUUVUUUUUUUUN 553 Inde
446. oating point errors turn debug messages on and enable floating point traps Set pfNotifyLevel PFNFY_DEBUG The goal is to have no NaN Not a Number INF infinite value or floating point exceptions resulting from numerical computations 475 Chapter 13 Performance Tuning and Debugging Notes on Tuning for RealityEngine Graphics 476 This section contains some specific notes on performance tuning with RealityEngine graphics Multisampling Multisampling provides full scene antialiasing with performance sufficient for a real time visual simulation application However it isn t free and it adds to the cost of some other fill operations With RealityEngine graphics most other modes are free until you add multisampling multisampling requires some fill operations to be performed on every subpixel This is most noticeable with z buffering and stenciling operations but also applies to blendfunction and glBlendFunc Texturing is an example of a fill operation that can be free on a RealityEngine and isn t affected by the use of multisampling The multisampling hardware reduces the cost of subpixel operations by optimizing for pixels that are fully opaque Pixels that have several primitives contributing to their result are thus more expensive to evaluate and are called complex pixels Scenes usually end up having a very low ratio of complex pixels Multisampling offers an additional performance optimization that helps
447. objects However in order to save substantial amounts of memory libpr objects such as pfGeoSets and pfGeoStates don t have frame accurate behavior modifications to such objects are immediately visible to all processes If you want frame accurate modifications to libpr objects you must use the passthrough data mechanism use a frame accurate pfSwitch to select among multiple copies of the objects you want to change or use the pfCycleBuffer memory type described in CycleBuffers on page 389 Chapter 8 Cre ating Visual Effects This chapter describes special visual features such as lighting backdrops and fog Chapter 8 Using pfEarthSky Creating Visual Effects This chapter describes how to use environmental atmospheric lighting and other visual effects to enhance the realism of your application A pfEarthSky is a special set of functions that clears a pfChannel s viewport efficiently and implements various atmospheric effects A pfEarthSky is attached to a pfChannel with pfChanESky Several pfEarthSky definitions can be created but only one can be in effect for any given channel at a time A pfEarthSky can be used to draw a sky and horizon to draw sky horizon and ground or just to clear the entire screen to a specific color and depth The colors of the sky horizon and ground can be changed in real time to simulate a specific time of day At the horizon boundary the ground and sky share a common colo
448. ocess priorities are used by the operating system to decide when and for how long processes should run A non degrading priority specifies that the process scheduling should not take into account how long the process has been running when deciding whether to let another process run The use of non degrading priorities is important for real time performance occlusion culling The discarding of objects which are not visible because they are occluded by other closer objects in the scene e g a city behind a mountain See also culling opera lighting The generic term for a powerful carbon arc lamp producing an intense light such as that invented by John H Kliegl and Anton T Klieg for use in public staged events and cinematographic undertakings that is often mounted within a dual gimballed exoskeletal framework to afford the lamp sufficient freedom of orientation that the projected beam can be made to track and highlight performers as they move across a stage The temperature of the thermal plasma that develops between the carbon electrodes of such arc lamps can be determined by spectroscopic investigation of its dissociated condition and has been found to be between 20 000 C and 50 000 C The term can also refer to a stage lighting technique that projects an image of a background scene onto the stage or screen Accurate visual simulation of both of these light types as well as common vehicle headlights airplane landing lights and searc
449. ocesses right hand rule Derived from a simple visual example for the direction of positive rotation about an axis the right hand rule states that the curled fingers of the right hand indicate the direction of positive rotation when the right hand is placed about the desired axis with the thumb pointing in the positive direction The positive angle is the one that rotates the primary axes toward each other For example a positive rotation counter clockwise about the X axis takes the positive Y axis into the position previously occupied by the positive Z axis 525 Glossary 526 roll In the context of X axis to the right Y axis forward and Z axis up then roll is rotation about the Y axis This is the rotation that would raise and lower the wings of an aircraft leading to a turn Also see Euler angles scene A collection of geometry to be rendered into a pfChannel scene complexity The complexity of the scene for rendering purposes in particular the amount of geometry transformations and graphics state changes in the scene scene graph A hierarchical assembly of IRIS Performer nodes linked by explicit attachment arcs that constitutes a virtual world definition for traversal and subsequent display search path A list of directory names given to IRIS Performer to specify where to look for data files which aren t specified as full path names sense An indication of whether a positive angle is interpreted
450. ode examples xxviii channels channel share group definition 511 channel share groups 105 configuring 92 108 creating 92 92 definition 511 multiple rendering 100 setting up 64 share mask definition 511 character animation 26 children of a node definition 512 circular references See references circular classes libpf pfBillboard 23 114 140 483 pfBuffer 220 484 pfChannel 73 92 484 pfDCS 114 126 156 483 pfEarthSky 32 93 231 484 pfFrameStats 425 pfGeode 114 137 483 pfGroup 114 483 pfLayer 114 131 483 pfLightPoint 32 114 132 483 pfLightSource 26 114 133 483 pfLOD 114 130 483 pfLODState 484 pfMorph 26 114 153 483 pfNode 112 114 115 116 119 483 pfPartition 114 144 483 pfPath 484 pfPipe 73 75 484 pfPipeWindow 73 79 484 pfScene 73 114 125 483 pfSCS 114 126 156 483 pfSequence 114 128 483 pfSwitch 114 127 484 pfText 114 484 pfTraverser 484 libpfdu pfdBuilder 262 pfdGeom 266 pfdPrim 267 libpr pfBox 408 485 pfColortable 484 pfCycleBuffer 389 485 pfCycleMemory 389 485 pfCylinder 409 485 pfDataPool 388 485 pfDispList 33 450 484 pfFile 485 pfFog 484 pfFont 328 484 pfFrustum 485 pfGeoSet 32 320 450 484 pfGeoState 33 484 pfHighlight 484 pfHit 417 484 pfLlight 485 pfLightModel 485 pfList 485 pfLPointState 32 132 237 484 pfMaterial 485 pfMatrix 399 485 pfMatStack 407 485 pfMemory 48
451. of the parent pipe with pfAttachPWin 81 Chapter 4 Setting Up the Display Environment 82 pfPipeWindows have a target default framebuffer configuration The ability to meet this target will depend on the current graphics hardware configuration as well as their type The following parameters are part of the target default configuration and are listed in their order of priority If the goal framebuffer configuration cannot be created on the current graphics hardware configuration lower priority parameters will be downgraded as specified e double buffered e RGB mode with eight bits per color component four if eight cannot be supported e z buffer with depth of 24 bits e one bit stencil buffer windows type PFWIN_TYPE_STATS will still require 4 bits of stencil e multisample buffer of eight four or zero samples as available e four bit stencil buffer pfPipeWindows have IRIS Performer ibpr rendering state automatically initialized when they are opened Additionally the following graphics state is automatically initialized upon opening or upon any call to pfInitGfx for an open window e in pure IRIS GL windows the framebuffer configuration is restored to default however if multisample buffers already exist the default multisampled configuration is used e RGB mode is enabled e z buffer is enabled and a z range is set e viewport clipping is enabled e subpixel vertex accuracy is enabled e the v
452. oftware PRISMS ASCII data ptu Simple IRIS Performer terrain data format slk US ARMY SIMNET database format sgf US Naval Academy standard graphics format sgo Paul Haeberli s graphics data format spf US Naval Academy simple polygon format sponge Sierpinski sponge 3D fractal generator star Astronomical data from Yale University star chart stla 3D Structures ASCII stereolithography data stlb 3D Structures binary stereolithography data stm Michael Garland s terrain data format sv John Kichury s i3dm modeler format Description of Supported Formats Table 9 6 continued Supported Database Formats Name Description tri University of Minnesota Geometry Center data unc University of North Carolina walkthrough data Description of Supported Formats AutoDesk 3DS Format The AutoDesk 3DS format is used by the 3DStudio program and by a number of 3D file interchange tools The IRIS Performer loader for 3DS files is located in the usr share Performer src lib libpfdb libpf3ds directory This loader uses an auxiliary library 3dsftk a to parse and interpret the 3ds file pfdLoadFile uses the function pfdLoadFile_3ds to import data from 3DStudio files into IRIS Performer run time data structures Silicon Graphics BIN Format The Silicon Graphics BIN format is supported by both Showcase and the powerflip demonstration program BIN files are in a simple format that specifies only independent quadrilaterals The image
453. oid InitChannel int NumChans Initialize all channels on pipe 0 for i 0 i lt NumChans i Chan i pfNewChan pfGetPipe 0 Make channel n 2 the master channel can be any channel x7 ViewState gt masterChan Chan NumChans 2 107 Chapter 4 Setting Up the Display Environment 108 Attach all Channels as slaves to the master channel for i 0 i lt NumChans i if Chan i ViewState gt masterChan pfAttachChan ViewState gt masterChan Chan i pfSetVec3 xyz 0 0f 0 0f 0 0f Set each channel s viewing offset In this case use many channels to create one multichannel contiguous frustum with a 45 field of fiew for i 0 i lt NumChans i float fov 45 0f NumChans pfSetVec3 hpr NumChans 1 0 5f i fov O20 Or OEN pfChanViewOffsets Chan i xyz hpr Now just configure the master channel and all of the other channels will share those attributes EJ chan ViewState gt masterChan pfChanTravFunc chan PFTRAV_CULL CullFunc pfChanTravFunc chan PFTRAV_DRAW DrawFunc pfChanScene chan ViewState gt scene pfChanESky chan ViewState gt eSky pfChanNearFar chan ViewState gt near ViewState gt far pfChanFOV chan 45 0f NumChans 1 0f pfChanView chan ViewState gt initView xyz ViewState gt initView hpr Chapter 5 Nodes and Node Types This chapter describes the struct
454. olor Description of Supported Formats If the material directive exists within a model description the format is material n Where n is an integer specifying which material as defined by the material description above is to be assigned to subsequent data Texture definition If the texture directive exists before a model definition it is taken as a new texture specification Its format is n TextureFileNam textur If the texture directive exists within a model description the format is texture n Where n is an integer specifying which texture as defined by the texture description above is to be assigned to subsequent data Backface polygon display mode The backface directive is specified within model definitions to control backface polygon culling backfac e mode Where a mode of on allows the display of backfacing polygons and a mode of off suppresses their display In actual use the SV format is somewhat self documenting Here is part of the SV file apple sv from the usr share Performer data directory material 20 0 0 0 0 0 0 400000 0 000000 0 0 333333 0 000000 0 0 10 0000 0 0 0 material 42 0 2 0 2 0 0 666667 0 666667 0 0 800000 0 800000 0 8 94 1606 0 0 O material 44 0 0 0 2 0 0 000000 0 200000 0 0 000000 0 266667 0 0 5 0000 0 0 0 texture 4 prchmnt rgb texture 6 wood rgb model LEAF material 44 texture 4 backface on poly3dn 4 text tured 1 35265 1 35761 13 8338 0 0686595
455. olygon for the POLYS primitive type The number of line segments in a line strip is numVerts 1 while the number of triangles in a triangle strip and polygon is numVerts 2 Use pfGSetPrimLengths to set the length array for strip primitives The number of primitives in a pfGeoSet is specified by pfGSetNumPrims gset num For strip and polygon primitives num is the number of strips or polygons in gset pfGeoSet Draw Mode In addition to the primitive type pfGSetDrawMode further defines how a primitive is drawn Triangles triangle strips quadrilaterals and polygons can be specified as either filled or as wireframe where only the outline of the primitive is drawn Use the PFGS_WIREFRAME argument to enable disable wireframe mode Another argument PFGS_FLATSHADE specifies how the primitive should be shaded If flat shading is enabled each primitive or element in a strip is shaded with a single color Geometry pfGeoSets are normally processed in immediate mode which means that pfDrawGSet sends attributes from the user supplied attribute arrays to the Graphics Pipeline for rendering However this kind of processing is subject to some overhead particularly if the pfGeoSet contains few primitives In some cases it may help to use GL display lists this is different from the libpr display list type pfDispList or compiled mode In compiled mode pfGeoSet attributes are copied from the attribute lists into a special data structure c
456. on Two useful criteria provided by IRIS Performer are sorting by graphics state and sorting by range When sorting by state pfGeoSets are sorted first by their pfGeoState then by an application specified hierarchy of state modes values and attributes which are identified by PFSTATE_ tokens and are described in the libpr chapter State sorting can offer a huge performance advantage since it greatly reduces the number of mode changes carried out by the Geometry Pipeline State sorting is the default sorting configuration for the opaque bin Range sorting is required for proper rendering of blended transparent surfaces which must be rendered in back to front order so that each surface is properly blended with the current background color Front to back sorting is also supported The default sorting for the transparent bin is back to front sorting Note that the sorting granularity is per pfGeoSet not per triangle so transparency sorting is not perfect pfChannel bins are given rendering order and sorting configuration with pfChanBinOrder and pfChanBinSort respectively A bin s order is simply an integer identifying its place in the list of bins An order less than 0 or PFSORT_NO_ORDER means that pfGeoSets which fall into the bin are drawn immediately without any ordering or sorting Multiple bins may have the same order but the rendering precedence among these bins is undefined A bin s sorting configuration is given as a token identif
457. one in which just the right amount of control is supplied to maintain the 211 Chapter 7 Frame and Load Control 212 frame rate without introducing undesirable effects The effects of overdamped and underdamped systems are visually distracting An underdamped system oscillates causing the system to continuously alternate between two different LOD models without reaching equilibrium Overdamped systems may fail to react within the time required to maintain the desired frame rate In practice though dynamic load management works well and simple stress functions can handle the slowly changing loads presented by many databases The default stress function is controlled with user selectable parameters These parameters are set using the function pfChanStressFilter The default stress function is implemented by the code fragment in Example 7 3 Example 7 3 Default Stress Function current load curLoad drawTime frameRate frameFrac integrated over time if curLoad lt lowLoad stressLevel stressParam stressLevel else if curLoad gt highLoad stressLevel stressParam stressLevel limited to desired range if stressLevel lt 1 0 1 0 stressLevel else Vv if stressLevel maxStress maxStress stressLevel The parameters lowLoad and highLoad define a comfort zone for the control system The first if test in the code fragment demonstrates
458. onfig and expected by GLXlink for creating a framebuffer configuration and graphics window You can set and get this special GL dependent attribute array with pfWinFBConfigData and pfGetWinFBConfigData respectively This configuration array is useful for hooking up GLX windows with X windows from other toolkits or with Motif Under OpenGL operation pfWinFBConfigData just expects a configuration attribute array appropriate for g XChooseVisual or pfChooseWinFBConfig pfWindows and GL Windows libpr allows you direct access to the GL and X window handles or to create your own windows and set them on the pfWindow You can create your own windows and or in the case of OpenGL X graphics contexts and set them on the pfWindow You can then call pfOpenWin to make sure everything is hooked up correctly apply any specified origin and size and to initialize your IRIS Performer state Under pure IRIS GL operation a window and a graphics context are the same thing A pure IRIS GL window is created with the winopen command and can be assigned to the pfWindow with pfWinWSDrawable or pfWinGLCxt pfOpenWin will automatically call pfInitGfx and will automatically create a new pfState for your window If you have your own window management and do not call pfOpenWin then you should definitely call pfInitGfx to initialize the window s graphics state for IRIS Performer rendering and you will also need to call pfNewState to cre
459. ons which include e the signature a text string that identifies the file e the header which contains global file information e the material table defining material properties 289 Chapter 9 Importing Databases 290 e the layer table defining grouping and association e the texture table referencing texture images e geometry in the form of clusters The format of the geometric clusters is somewhat complicated A cluster is a group of coplanar surfaces called patches that share a common material layer and normal Each patch shares at least one edge with another patch in the cluster Each patch defines either a convex quadrilateral or a triangle and patches represent quad trees called nodes Each node points to its corner vertices and its children The leaf nodes point to their corner vertices and the child pointers can optionally point to the vertices that split an edge of the node Only the locations of vertices that are corners of the patches are stored in the file other vertices are created by subdividing nodes of the quad tree as the LSB file is loaded The color information for each vertex is unique and is specified in the file The image in Figure 9 8 shows an LSB format database developed during the design of a hospital operating room This database was produced by the DeWolff Partnership of Rochester New York using the Lightscape Visualization system Description of Supported Formats Figure 9 8 LSB Forma
460. onverters but also to set and get modes attributes and values that might affect the converter s methodology Table 9 4 libpfdu database converter management functions Function Name Description pfdInitConverter Initialize a database conversion DSO pfdExitConverter Exit a database conversion DSO pfdConverterMode Specify a mode for a specific conversion DSO pfdGetConverterMode Geta mode setting from a specific conversion DSO pfdConverterAttr Specify an attribute for a conversion DSO pfdGetConverterAttr Get an attribute setting from a conversion DSO pfdConverterVal Specify a value for a conversion DSO pfdGetConverterVal Get a value setting from a conversion DSO Once again each converter provides the equivalent routines with EXT added to the function name 255 Chapter 9 Importing Databases 256 For example the converter for the Open Inventor format would define the function pfdInitConverter_iv if it needed to be initialized before it was used Likewise it would define the function pfdLoadFile_iv to read an Open Inventor iv file into an IRIS Performer scene graph Note Because each converter is an individual entity DSO and deals with a particular type of database it may be the case that a converter will not provide all of the functionality listed above but rather only a subset For instance most converters that come with IRIS Performer 2 0 only implement their version of pfdLoadFile but not pfdStoreFil
461. opaque or transparent bins Paths Through the Scene Graph You can define a chain or path of nodes in a scene graph using the pfPath data structure Note that a pfPath has nothing to do with filesystem paths as specified with the PFPATH environment variable or with specifying a path for a user to travel through a scene Once you ve specified a pfPath with a call to pfNewPath you can traverse and cull that path as a subset of the entire scene graph using pfCullPath Call he function pfCullPath must only from the cull callback function set by pfChanTravFunc see Process Callbacks on page 174 for details For more information about the pfPath structure see the pfPath pf and pfList 3pf reference pages When IRIS Performer looks for intersections it can return a pfPath to the node containing the intersection This feature is particularly useful when you re using instancing in which case you can t use pfGetParent to find Draw Traversal out where in the scene graph the given node is Finding out the pfPath to a given node is also useful in implementing picking for an example see the source code in usr share Performer src sample apps C pickfly picking c or execute usr share Performer bin pickfly if it is installed on your system When you click on an object in a scene this program prints the path to the node you ve picked Draw Traversal The cull traversal generates a libpr display list of geometry and state
462. or Debugging For detailed information about other aspects of shared memory see Memory Allocation in Chapter 10 Use the Simplest Process Model When debugging an application that uses a multiprocess model first use a single process model to verify the basic paths of execution in the program You don t have to restructure your code simply select single process operation by calling pfMultiprocess PFMP_APPCULLDRAW to force all tasks to initiate execution sequentially on a frame by frame basis If an application fails to run in multiprocess mode but runs smoothly in single process mode you may havea problem with the initialization and use of data that s shared among processes If you need to debug one of multiple processes use IRIS dbx p progname while the process is running This will show the related processes and allow you to choose a process to trace The application process will always be the process with the lowest process id In order after that will be the default clock process then the cull process and then the draw Once the program works experiment with the different multiprocess models to achieve the best overall frame rate for a given machine Don t specify more processes than CPUs Use pfDrawChanStats to compare the frame timings of the different stages and frame times for the different process models Avoid Floating Point Exceptions Arrange error handling for floating point operations To see fl
463. ormer applications Required Libraries The following libraries are required when linking an executable libpf libpr IRIS Performer visual simulation development library Comes in two version libpf_ogl and libpf_igl for OpenGL and IRIS GL respectively IRIS Performer high performance rendering library Exists in both OpenGL and IRIS GL versions and is contained within the corresponding libpf libpf_ogl and libpf_igl for OpenGL and IRIS GL respectively libpfdu libpfutil libimage libGLU libGL libXext libGLw libxm libXt libXmu libX11 IRIS Performer database library does file handling and includes importers for a variety of data formats Comes in two version libpfdu_ogl and libpfdu_igl for OpenGL and IRIS GL respectively IRIS Performer utilities library includes the window related functions Comes in two version libpfutil_ogl and libpfutil_igl for OpenGL and IRIS GL respectively Image library required by libpr OpenGL utilities library required by libpr with OpenGL OpenGL graphics library either this or the alternative libg the IRIS GL graphics library is required by libpf and libpr OpenGL widget library for using OpenGL with IRIS IM IRIS IM library used for Silicon Graphics look windows X toolkit intrinsics library used by IRIS IM X Window System library equired by libgl and libpr 67 Chapter 3 Building a Visual Simulation Application 68 f Advanced
464. ormer pf pfGroup h gt pfLOD lt Performer pf pfLOD h gt pfLayer lt Performer pf pfLayer h gt pfLightPoint lt Performer pf pfLightPoint h gt pfLightSource lt Performer pf pfLightSource h gt pfMorph lt Performer pf pfMorph h gt pfNode lt Performer pf pfNode h gt pfPartition lt Performer pf pfPartition h gt pfSCS lt Performer pf pfSCS h gt pfScene lt Performer pf pfScene h gt pfSequence lt Performer pf pfSequence h gt 483 Chapter 14 Programming with C 484 Table 14 2 continued Header Files for libpf Scene Graph Node Classes libpf Class Include File pfSwitch lt Performer pf pfSwitch h gt pfText lt Performer pf pfText h gt Table 14 3 Header Files for Other libpf Classes libpf Class Include File pfBuffer lt Performer pf pfBuffer h gt pfChannel lt Performer pf pfChannel h gt pfEarthSky lt Performer pf pfEarthSky h gt pfLODState lt Performer pf pfLODState h gt pfPipe lt Performer pf pfPipe h gt pfPipeWindow lt Performer pf pfPipeWindow h gt pfIraverser lt Performer pf pfTraverser h gt pfPath Table 14 4 Header Files for libpr Graphics Classes libpr Class Include File pfColortable lt Performer pr pfColortable h gt pfDispList lt Performer pr pfDispList h gt pfFog lt Performer pr pfFog h gt pfFont lt Performer pr pfFont h gt pfGeoSet lt Performer pr pfGeoSet h gt pfHit pfGeoState lt Performer pr pfGeoState h gt pfHighlight lt Performer pr pfHighlight h gt
465. orrespond to enabled classes of statistics For more information about specific statistics classes see the pfFrameStats 3pf and pfStats 3pf reference pages Reducing the Cost of Statistics Collecting and displaying statistics can have a big impact on performance This section describes ways to reduce that impact Enabling Only Statistics of Interest Each channel has its Process Frame Times PFTIMES statistics class enabled by default This class maintains a short history of process frames times as well as averaging frame times over the default update period of two seconds To minimize unnecessary overhead turn off statistics on channels when you re not using them To turn off all statistics for a channel call pfFStatsClass in the application process with the statistics structure of the given channel pfFStatsClass pfGetChanFStats chan PFSTATS_ALL PFSTATS_OFF Each statistics class has default mode settings The short history of process frame time is used to draw the timing graph By default this history consists of four frames of each IRIS Performer process app cull draw intersections Maintaining this short history of statistics can be disabled by calling pfStatsClassMode with the token PFFSTATS_PFTIMES_HIST pfStatsClassMode fstats PFFSTATS_PFTIMES PFFSTATS_PFTIMES_HIST PFSTATS_OFF 439 Chapter 12 Statistics 440 This is useful if you re only interested in the average frame tim
466. ote Both OpenGL and IRIS GL versions of perfly are installed in usr sbin The perfly command invokes the one more appropriate for your particular graphics hardware To explicitly invoke the OpenGL or IRIS GL versions run perfly_ogl or perfly_igl respectively The perfly program allows several motion models the d on the command line tells the program to start in the Drive model which provides an easy way to drive or walk through a scene while maintaining a fixed height above the ground When you want to quit perfly either press the lt Esc gt key or click the Quit button on the control panel Exploring the IRIS Performer Sample Scenes Look Around Look around the scene using the mouse First place the cursor in the center of the simulation window Now depress the middle mouse button and move the mouse to the left and to the right to turn in place you ll continue to pivot until you place the cursor back in the center of the screen Don t despair if you inadvertently start moving around lose sight of the building or otherwise lose position or control Just move the cursor into the control panel area and click the Reset All button on the control panel to get back to the original setup Approach the Building To approach the City Hall model turn until you re facing it if you aren t already facing it and then center the mouse in the screen Depress the left mouse button briefly to start accelerating forward
467. oth query routines immediately halt and return with the total number of bytes successfully written There are specific tokens for querying individual values or entire classes of statistics The query tokens are of the form PFSTATSVAL_ and PFFSTATSVAL_ and the corresponding exposed structure names are of the form pfStatsVal and pfFStats Val Queries on pfFrameStats structures with PFFSTATSVAL_ tokens expect a PFFSTATS_BUF_ select token to be ORed with the query select It s an error to include more than one pfFrameStats buffer select token If no buffer select token is provided the CUR buffer will be queried The statistics query tokens and structures are defined in prstats h and pfstats h Customizing Displays The standard statistics displays have several parameters hard wired in For instance you can t change the colors used in such displays If you want to use different colors you ll have to use your own display routines Setting Update Rate To set the frequency at which statistics are automatically collected use pfFStatsAttr See the pfFrameStats 3pf reference page for details If you want to turn off cumulative statistics collection and thus running averages entirely set the update rate to zero Note that doing this will change your Collecting and Accessing Statistics in Your Application statistics display in particular your actual frame rate will be changed to 222 and other averages will not be display
468. ou can select which buffers are to be printed PREV CUR AVG or CUM The selected statistics Collecting and Accessing Statistics in Your Application from all selected buffers are printed The following call prints the currently enabled statistics from the previous frame and from the averaged statistics buffer pfPrint stats PFFSTATS_BUF_PREV PFFSTATS_BUF_AVG pfGetStatsClass stats PFSTATS_ALL PFPRINT_VB_INFO 0 Copying You can copy entire pfStats and pfFrameStats structures with the general pfCopy command pfCopy copies all of the statistics data as well as information on mode settings and which classes are enabled The source and destination structures must be of the same type If both statistics structures are pfFrameStats structures then all statistics from all buffers are copied The pfCopyStats and pfCopyFStats routines copies only statistics data not class enables or mode settings and accepts a class enable bitmask to select statistics classes for the copy For example pfCopyStats statsA statsB pfGetStatsClass statsB PFSTATS_ALL For a pfFrameStats structure a PFFSTATS_BUF_ token can be included in the stats enable bitmask to select the buffer to be accessed If no buffer is specified the CUR buffer is used For example pfCopyFStats fstats stats PFFSTATS_BUF_PREV pfGetStatsClass stats PFSTATS_ALL copies the currently enabled classes of stats to the PREV pfStats in
469. ould be called only from the appropriate processes see Table 7 4 Table 7 4 Trigger Routines and Associated Processes Trigger Routine Process Context pfAppFrame APP main loop pfSync pfFrame pfPassChanData APP main loop pfPassIsectData pfApp APP channel APP callback pfCull CULL channel CULL callback pfCullPath pfDraw DRAW channel DRAW callback pfDrawBin pfNodelsectSegs ISECT callback or APP main loop pfChanNodelsectSegs pfDBase DBASE callback e User spawned processes created with sproc can trigger parallel intersection traversals through multiple calls to pfNodeIsectSegs and pfChanNodelsectSegs e Functions pfApp0 pfCull0 pfDraw and pfDBase are only called from within the corresponding callback specified by pfChanTravFunc or pfDBaseFunc 225 Chapter 7 Frame and Load Control 226 Multiprocessing and Memory In IRIS Performer as is often true of multiprocessing systems memory management is the most difficult aspect of multiprocessing Most data management problems in an IRIS Performer application can be partitioned into three categories e Memory visibility IRIS Performer uses fork which unlike sproc Q generates processes that don t share the same address space The processes also cannot share global variables that are modified after the fork call After calling fork processes must communicate through explicit shared memory e Memory exclusion If multiple process
470. p of segments with the subgraph rooted at the specified node pfChanNodelsectSegs functions similarly but includes a channel so that the traversal can make decisions based on the level of detail specified by pfLOD nodes 179 Chapter 6 Database Traversal 180 Intersection Requests pfSegSets A pfSegSet is a structure that embodies an intersection request typedef struct _pfSegSet long mode void userData pfSeg segs PFIS_MAX_SEGS ulong activeMask ulong isectMask void bound long discFunc pfHit pfSegSet The segs field is an array of line segments making up the query You tell pfNodelsectSegs which segments to test with by setting the corresponding bit in the activeMask field If your pfSegSet contains many closely grouped line segments you can specify a bounding volume using the data structure s bound field pfNodelIsectSegs can use that bounding volume to more quickly test the request against bounding volumes in the scene graph The user Data field is a pointer with which you can point to other information about the request that you might want access to in a callback The other fields are described below The pfSegSet isn t modified during the traversal Intersection Return Data pfHit Objects Intersection information is returned in pfHit objects These can be queried using pfQueryHit and pfMQueryHit Table 6 3 lists the items that can be queried from a pfHit object Table 6 3 Inte
471. pagated through the pipeline stages by cycling the pfCycleMemories 389 Chapter 10 libpr Basics 390 Figure 10 4 pfCycleBuffer and pfCycleMemory Overview Cycling the memory buffers works if each current pfCycleMemory is completely updated each frame If this is not the case buffer cycling will eventually access a stale pfCycleMemory whose contents were valid some number of frames ago but are invalid now pfCycleBuffers manage this by frame stamping a pfCycleMemory whenever pfCBufferChanged is called The global frame count is advanced with pfCBufferFrame which also copies most recent pfCycleMemories into stale pfCycleMemories thereby automatically keeping all pfCycleBuffers current Managing Nongraphic System Tasks A pfCycleBuffer consisting of pfCycleMemories of nbytes size is allocated from memory arena with pfNewCBuffer nbytes arena To initialize all the pfCycleMemories of a pfCycleBuffer to the same data call pfInitCBuffer pfCycleMemory is derived from pfMemory so you can use inherited routines like pfCopy pfGetSize and pfGetArena on pfCycleMemories While pfCycleBuffers may be used for application data their primary use is as pfGeoSet attribute arrays e g coordinates or colors pfGeoSets accept pfCycleBuffers or pfCycleMemory references as attribute references and automatically select the proper pfCycleMemory when drawing or intersecting with the pfGeoSet Note Jibpf applications
472. pecify a light source with limited influence Node Types Table 5 8 describes the functions for working with pfLightSources Table 5 8 pfLightSource Functions Function Description pfNewLSource Create a new pfLightSource node pfLightAmbient Set the ambient color for a pfLight pfGetLightAmbient Get the ambient color for a pfLight pfLightColor Set the color for a pfLight pfGetLightColor Find out the color of a pfLight pfSpotLightDir Aim a spotlight in the given direction pfGetSpotLightDir Determine the direction a spotlight is pointing pfSpotLightCone Set the width of a spotlight cone pfGetSpotLightCone Find out the width of a spotlight cone pfLightPos Set the position of a light pfGetLightPos Get the position of a light pfIsLightOn Determine whether a light is on or off pfLightOn Enable a light execute saved up modifications to the light pfLightOff Disable a light pfGeode Nodes pfGeode is short for geometry node and is the primary node for defining geometry in libpf A pfGeode contains a list of geometry structures called pfGeoSets which are part of the IRIS Performer libpr library pf GeoSets encapsulate graphics state and geometry and are described in the Geometry Sets section of Chapter 10 libpr Basics It is important to understand that pfGeoSets are not nodes but are simply elements of a pfGeode 137 Chapter 5 Nodes and Node Types 138 Table 5 9 describes the functions fo
473. perations 404 pfPreMultMat m1 m2 pfinvertAffMat m3 ml pfPostMultMat m3 m1 AssertEqMat m3 ident affine inverse A pfQuat is the IRIS Performer data structure a pfVec4 whose for floating point values represent the components of a quaternion Quaternions have many beneficial properties The most relevant of these is their ability to represent 3D rotations in a manner that allows relatively simple yet meaningful interpolation between rotations Much like multiplying two matrices multiplying two quaternions results in the concatenation of the transformations For more information on quaternions see the article by Sir William Rowan Hamilton On quaternions or on a new system of imaginaries in algebra in the Philosophical Magazine xxv pp 10 13 July 1844 or refer to the sources noted in the pfQuat 3pf reference page The properties of spherical linear interpolation makes quaternions much better suited than matrices for interpolating transformation values from keyframes in animations The most common usage then is to use pfSlerpQuat to interpolate between two quaternions representing two rotational transformations The quaternion that results from the interpolation can then be passed to pfMakeQuatMat to generate a matrix for use in a subsequent IRIS Performer call such as pf DCSMat While converting a quaternion to a matrix is relatively efficient converting a matrix to a quaternion with pfGetOrthoMatQu
474. perator new and deleted with operator delete Objects of these classes cannot be created statically on the stack or in arrays The default new operator creates objects in the current shared memory arena if one exists libpr objects and public structs have an additional new operator that takes an arena argument This new operator allows allocation from the heap indicated by an arena of NULL or from a shared memory arena created by the application with IRIX acreate Example 14 1 Legal Creation of Objects in C legal creation of libpf objects pf DCs dcs new pfDCS only way legal creation of libpr objects pfGeoSet gs new pfGeoSet from default arena pfGeoSet gs new NULL pfGeoSet from heap legal creation of public structs pfVec3 vert new pfVec3 from default arena pfVec3 verts new pfVec3 10 array from default static pfVec3 vert 0 0f 0 0f 0 0f static Programming Basics Example 14 2 Illegal Creation of Objects in C illegal creation of libpf objects pfDCS dcs new NULL pfDCS not in shared mem pfDCs dcs new pfDCS 10 array illegal creation of libpr objects pfGeoSet gs new pfGeoSet 10 array illegal creation of public structs pfVec3 vert new NULL pfVec3 10 array non default new Caution This last item in Example 14 2 is illegal because C does not provide a mechanism to delete arrays of objects allocated with
475. pfLPointState lt Performer pr pfLPointState h gt Programming Basics Table 14 4 continued Header Files for libpr Graphics Classes libpr Class Include File pfLight lt Performer pr pfLight h gt pfLightModel pfMaterial lt Performer pr pfMaterial h gt pfSprite lt Performer pr pfSprite h gt pfState lt Performer pr pfState h gt pfString lt Performer pr pfString h gt pfTexture lt Performer pr pfTexture h gt pflexGen pfTexEnv Table 14 5 Header Files for Other libpr Classes libpr Class pfCycleBuffer pfCycleMemory pfDataPool pfFile pfSphere pfBox pfCylinder pfPolytope pfFrustum pfSeg pfSegSet pfVec2 pfVec3 pfVec4 pfMatrix pfQuat pfMatStack pfList Include File lt Performer pr pfCycleBuffer h gt lt Performer pr pfDataPool h gt lt Performer pr pfFile h gt lt Performer pr pfGeoMath h gt lt Performer pr pfLinMath h gt lt Performer pr pfList h gt 485 Chapter 14 Programming with C 486 Table 14 5 continued Header Files for Other libpr Classes libpr Class Include File pfMemory lt Performer pr pfMemory h gt pfObject lt Performer pr pfObject h gt pfStats lt Performer pr pfStats h pfType lt Performer pr pfType h pfWindow lt Performer pr pfWindow h Creating and Deleting IRIS Performer Objects The IRIS Performer base classes all provide operator new and operator delete All libpr and libpf objects must be explicitly created with o
476. pfNewHlight encapsulates the state elements and modes for these rendering styles A pfHighlight can be applied to an individual pfGeoSet with pfGSetHlight or can be applied to multiple pfGeoStates through a pfGeoState or pfApplyHlight The highlighting effects are added to the normal rendering phase of the geometry pfHighlights make use of special outlining and fill modes and have a concept of a foreground color and a background color that can both be set with pfHlightColor The available rendering styles can be combined by OR ing together tokens for pfHlightMode and are described in Table 10 15 Table 10 15 pfHlightMode Tokens PFHL_ Mode Bitmask Token Description LINES Outlines the triangles in the highlight foreground color according to pfHlightLineWidth LINESPAT Outlines triangles with patterned lines in the LINESPAT2 highlight foreground color or in two colors using the background color 351 Chapter 10 libpr Basics 352 Table 10 15 continued pfHlightMode Tokens PFHL_ Mode Bitmask Token Description FILL Draws geometry with the highlight foreground color Combined with SKIP_BASE this is a fast highlighting mode FILLPAT Draws the highlighted geometry as patterned with FILLPAT2 one or two colors FILLTEX Draw highlighting fill pass with a special highlight texture LINES_R Reverses the highlighting foreground and FILL_R background colors for lines and fill respectively POINTS R
477. pfNewSCS matrix to create a new pfSCS using the transformation defined by matrix To find out what matrix was used to create a given pfSCS call pfGetSCSMat For best graphics performance matrices passed to pfSCS nodes and the pfDCS node type described in the next section should be orthonormal translations rotations and uniform scales Nonuniform scaling requires renormalization of normals in the graphics pipe Projections and other non affine transformations are not supported While pfSCS nodes are useful in modeling using too many of them can reduce culling rendering and intersection performance For this reason libpf provides the pfFlatten traversal pfFlatten will traverse a scene graph and apply static transformations directly to geometry to eliminate the overhead associated with managing the transformations pfFlatten is described in detail in Chapter 6 Database Traversal pfDCS Nodes A pfDCS is a branch node that represents a dynamic coordinate system Use a pfDCS when you want to apply an initial transformation to a node and also change the transformation during the application Use a pfDCS to articulate moving parts and to show object motion Node Types Use pfNewDCS to create a new pfDCS The initial transformation of a pfDCS is the identity matrix Subsequent transformations are set by specifying a new transformation matrix or by replacing the rotation scale or translation in the current transfo
478. phics data format The image in Figure 9 6 shows a sample Open Inventor data file 285 Chapter 9 Importing Databases 286 Figure 9 6 Aircar Database in IRIS Inventor Format The model in Figure 9 6 represents one design for the perennial personal aircar of the future concept It was created using Imagine by Mike Halvorson of Impulse and was modeled after the Moller 400 as described in Popular Mechanics The Open Inventor data file loader provided with IRIS Performer reads both binary and ASCII format Open Inventor data files Open Inventor scene graph description files in both formats have the suffix iv appended to their file names Here is a simple Open Inventor file that defines a cone Inventor V2 1 ascii Separator Cone Description of Supported Formats The source code for the Open Inventor format importer is provided in the libpfdb libpfiv source directory pfdLoadFile uses the function pfdLoadFile_iv to load Open Inventor format files into IRIS Performer run time data structures Because VRML is a subset of Open Inventor 2 1 if you have Open Inventor 2 1 installed you can also read VRML wrl files using pfdLoadFile IRIS Performer also comes with an Inventor loader that works with Open Inventor 2 0 if Open Inventor 2 1 is not installed Lightscape Technologies LSA and LSB Formats The Lightscape Visualization system is a product of Lightscape Technologies Inc and
479. plosionl_seq pfNewSeq explosion2_seq pfNewSeq fae _ seq pfNewSeq smoke_seq pfNewSeq pfAddchild pfAddChild explosionl_seq fire_seq s pfAddChild s explosion2_seq s s pfAddChild smoke_seq pfSwitchVal s PFSWITCH_OFF if direct_hit pfSwitchVal s PFSWITCH_ON Select all sequences Set first explosion sequence to go double normal speed and repeat 3 times pfSeqMode explosionl_seq PFSEQ_START pfSeqDuration explosionl_seq 2 0f 3 Set second explosion sequence to display first child of sequence for 2 seconds before continuing pfSeqMode explosion2_seq PFSEQ_START pfSeqTime explosion2 0 0f 2 0f Set fire to wait on first frame of sequence until 3 seconds after second explosion pfSeqMode fire_segq PFSEQ_START pfSeqTime fire_seq 0 0f 2 3f Set smoke to wait until 1 seconds after fire pfSeqMode smoke_seq PFSEQ_ START pfSeqTime smoke_seq 0 0f 2 4f else if explosion amp amp expl_type 0 pfSeqMode explosionl_seq PFSEQ_START pfSwitchVal s 0 129 Chapter 5 Nodes and Node Types 130 else if explosion amp amp expl_type 1 pfSeqMode explosion2_seq PFSEQ_START pfSwitchVal s 1 else if fire_is_burning pfSeqMode fire_seq PFSEQ_START pfSwitchVal s 2 else if smoking
480. ports two kinds of instancing which are described in the following sections Shared Instancing Shared instancing is the result of simply adding a node to multiple parents If an instanced node has children then the entire subgraph rooted by the node is considered to be instanced Each parent shares the node thus modifications to the instanced node or its subgraph are experienced by all parents Shared instances can be nested that is an instance can itself instance other nodes In the following sample code group0 and group share a node pfAddcChild group0 node pfAddcChild groupl node Figure 5 2 shows the structure created by this code Before the instancing operation the two groups and the node to be shared all exist independently as shown in the left portion of the figure After the two function calls shown above the two groups both reference the same shared hierarchy If the original groups referenced other nodes those nodes would remain unchanged Note that each of the group nodes considers the shared hierarchy to be its own child Working With Nodes Group 1 Group 0 Group 1 Group 0 P rs Figure 5 2 Shared Instances Cloned Instancing In many situations shared instancing isn t desirable Consider a subgraph that represents a model of an airplane with articulations for ailerons elevator rudder and landing gear Shared instances of the model result in multiple planes that share the same artic
481. provide an image array in the same external format as specified on the pfTexture and as expected by texdef2d in IRIS GL and glTexImage2D in OpenGL IRIS GL and OpenGL both expect packed texture data with each row beginning ona long word boundary However IRIS GL and OpenGL expect the individual components of a texel to be packed in opposite order For example IRIS GL expects four component texels to be packed as ABGR OpenGL expects the texels to be packed as RGBA If you provide your own image array ina multiprocessing environment it should be allocated from shared memory along with your pflexture to allow different processes to access it Note The size of your texture must be an integral power of two on each side IRIS GL scales up your textures to the next power of two making them take up to four times more space in hardware texture memory OpenGL simply refuses to accept badly sized textures You can rescale your texture images with the izoom or imgworks programs shipped with IRIX 5 3 in the eoe2 sw imagetools and imgtools sw tools subsystems and with IRIX 6 2 in the eoe sw imagetools and imgworks sw tools subsystems Your texture source does not have to be a static image pfTexLoadMode can be used to set one of the sources listed in Table 10 11 with PFTEX_LOAD_BASE Note that sources other than CPU memory may not be supported on all graphics platforms or may have some special restrictions The sample program usr share Performer
482. quires a pass through the visual database to compare scene geometry with the current frame s viewing volume Any objects completely outside the frustum can be safely discarded Testing and culling a complex object requires less time than drawing it When simple view volume culling is insufficient to keep scene complexity constant it may be necessary to compute potential visibility of each object during the culling process by considering other objects within the scene that may occult the test object High performance image generation systems use comparable occlusion culling tests to reduce the polygon filling complexity of real time scenes Survey of Visual Simulation Techniques Rich Scene Content Several tricks and techniques can give the impression of rich scene content without actually requiring large quantities of complex geometry Level of Detail Selection Graphics systems can display only a finite number of geometric primitives per frame at a specified frame rate Because of these limitations the fundamental problem of database construction for real time simulation is to maximize visual cues and minimize scene complexity With level of detail selection one of several similar models of varying complexity is displayed based on how visible the object is from the eyepoint Level of detail selection is one of the best tools available for improving display performance by reducing database complexity For more detailed information see
483. r so that there is a smooth transition from sky to horizon color The width of the horizon band can be defined in degrees A pfChannel s earth sky model is automatically drawn by IRIS Performer before the scene is drawn unless the pfChannel has a draw callback set with pfChanTravFunc In this case it is the application s responsibility to clear the viewport Within the callback pfClearChan draws the channel s pfEarthSky Example 8 1 shows how to set up an pfEarthSky Example 8 1 How to Configure a pfEarthSky pfEarthSky esky pfChannel chan sky pfNewESky pfESkyMode esky PFES_BUFFER_CLEAR PFES_SKY_GRND pfESkyAttr esky PFES_GRND_HT 1 0f 231 Chapter 8 Creating Visual Effects Atmospheric Effects 232 pfESkyColor esky PFES_GRND_FAR 0 3f 0O 1f 0 0f 1 0f pfESkyColor esky PFES_GRND_NEAR 0 5f 0 3f O 1f 1 0f pfChanESky chan esky The complexities of atmospheric effects on visibility are approximated within IRIS Performer using a multiple layer sky model set up as part of the pfEarthSky function In this design individual layers are used to represent the effects of ground fog clear sky and clouds Figure 8 1 shows the identity and arrangement of these layers Atmospheric Effects a General f visibility A N Upper gt transition J zone gt Clouds A gt Lower transition zone A y General visibility
484. r appropriate for when passing pointers to typedefed arrays in C e g extern void pfFontCharSpacing pfFont font int ascii pfVec3 spacing because a pointer to a struct is passed in the same manner as a pointer to an array With the C API the main mechanism for extending the functionality of the classes provided in IRIS Performer is the specification of the user data pointer on pfObjects with pfUserData and the specification of callbacks on pfNodes with pfNodeTravFuncs and pfNodeTravData The C API also supports these mechanisms but also provides the additional capacity to subclass new data types from the classes defined in IRIS Performer Subclassing allows additional member data fields and functions to be added to IRIS Performer classes At it s simplest subclassing merely provides a way of adding additional data fields that is more elegant than hanging new data structures off of a pfObject s user data pointer But in some uses subclassing also allows significantly more control over the functional behavior of the new object because virtual functions can be overloaded to bypass replace or augment the processing handled by the parent class from IRIS Performer Subclassing pfObjects Initialization and Type Definition The new object should provide two static functions a constructor that initializes the instances pfType and a static data member for the type system as shown in the following table Table 14 6 Data a
485. r channels to share certain attributes For the three channel cockpit scenario each pfChannel shares the same eyepoint while the left and right views are offset using pfChan ViewOffsets IRIS Performer supports the notion of channel groups which facilitate attribute sharing between channels pfChannels can be gathered into channel groups that share like attributes A channel group is created by attaching one pfChannel to another or to an existing channel group Use pfAttachChan to create a channel group from two channels or to add a channel to an existing channel group Use pfDetachChan to remove a pfChannel from a channel group A channel share mask defines shared attributes for a channel group The attribute tokens listed in Table 4 3 are bitwise OR ed to create the share mask 105 Chapter 4 Setting Up the Display Environment 106 Table 4 3 Attributes in the Share Mask of a Channel Group Token Shared Attributes PFCHAN_FOV Horizontal and vertical fields of view PFCHAN_VIEW View position and orientation PFCHAN_VIEW_OFFSETS x y z and heading pitch roll offsets of the view direction PFCHAN_NEARFAR Near and far clipping planes PFCHAN_SCENE All channels display the same scene PFCHAN_EARTHSKY All channels display the same earth sky model PFCHAN_STRESS All channels use the same stress filter PFCHAN_LOD All channels use the same LOD modifiers PFCHAN_SWAPBUFFERS All channels swap buffers at the same time
486. r rendering The node and channel draw masks are logically AND ed together during the CULL traversal which prunes the node if the result is zero Draw masks may be used to categorize the scene graph where each bit represents a particular characteristic Each node contains these masks binary values whose bits serve as flags to indicate if the node and its children are considered drawable intersectable pickable and so on Most of these bits are available for application use drop Refers to frame processing When in locked or fixed phase and a processing stage takes too long the frame is dropped and not rendered Dropped frames are a sure sign of system overload 515 Glossary 516 DSO See dynamic shared object dynamic Something that is updated automatically when one of its attributes or children in a scene graph changes Often refers to the update of hierarchical bounding volumes in the scene graph dynamic shared object A Library which is not copied into the final application executable file but is instead loaded dynamically that is when the application is launched Since DSOs are shared only one copy of a given DSO is loaded into memory at a time no matter how many applications are using it DSOs also provide the dynamic binding mechanism used by the IRIS Performer database loaders Euler angles A set of three angles used to represent a rotation See heading pitch and roll fixed frame rate Rendering
487. r the escapement translations that happen Scale after each character is drawn This routine is useful for changing the spacing between characters and even between lines Graphics State Graphics State The graphics libraries are immediate mode state machines if you set a mode all subsequent geometry is drawn in that mode For the best performance mode changes need to be minimized and managed carefully libpr manages a subset of graphics library state and identifies bits of state as graphics state elements Each state element is identified with a PFSTATE token e g PFSTATE_TRANSPARENCY corresponds to the transparency state element State elements are loosely partitioned into three categories modes values and attributes Modes are the graphics state variables such as transparency and texture enable that have simple values like ON and OFF An example of a mode command is pfTransparency mode Values are not modal rather they are real numbers which signify a threshold or quantity An example of a value is the reference alpha value specified with the pfAlphaFunc command Attributes are references to encapsulations structures of graphics state They logically group the more complicated elements of state such as textures and lighting models Attributes are structures that are modified through a procedural interface and must be applied to have an effect For example pfApplyTex tex applies the texture map tex to subsequently d
488. r working with pfGeodes Table 5 9 pfGeode Functions Function Description pfNewGeode Create a pfGeode pfAddGSet Add a pfGeoSet pfRemoveGSet Remove a pfGeoSet pfInsertGSet Insert a pfGeoSet pfReplaceGSet Replace a pfGeoSet pfGetGSet Supply a pointer to the specified pfGeoSet pfGetNumGSets Determine how many pfGeoSets are in the given pfGeode Example 5 10 shows how to attach several pfGeoSets to a pfGeode Example 5 10 Adding pfGeoSets to a pfGeode pfGeode carl pfGeoSet muffler frame windows seats tires muffler read_in_muffler_geometry frame read_in_frame_geometry j seats read_in_seat_geometry tires read_in_tire_geometry pfAddGSet carl muffler pfAddGSet carl frame pfAddGSet carl seats pfText Nodes A pfText node is libpf leaf node that contains a set of libpr pfStrings that should be rendered based on the libpf cull and draw traversals In this sense a pfText is similar to a pfGeode except that it renders 3 dimensional text through the libpr pfString and pfFont mechanisms rather than rendering standard 3 dimensional geometry via libpr pfGeoSet and pfGeoState Node Types functionality pfText nodes are useful for displaying 3 dimensional text and other collections of geometry from a fixed index list Table 5 10 lists the major pfText functions Table 5 10 pfText Functions Function Description pfNewText Create a pfText pfAddString Add a pfString
489. rame rate is to select an update rate constrained by the most complex portion of the visual database Although this conservative approach may be acceptable in some cases IRIS Performer supports a more sophisticated approach using dynamic LOD scaling Using multiple LOD models throughout a database provides the traversal system with a parameter that can be used to control the polygonal complexity of models in the scene The complexity of database objects can be reduced or increased by adjusting a global LOD range multiplier that determines which LOD level is drawn Dynamic Load Management Using this facility a closed loop control system can be constructed that adjusts the LOD switching criteria based on the system load also called stress in order to maintain a selected frame rate Figure 7 4 illustrates a stress processing control system Desired Frame Time Actual Frame Time Figure 7 4 Stress Processing In Figure 7 4 the desired and actual frame times are compared by the stress filter Based on the user supplied stress parameters the stress filter adjusts the global LOD scale factor by increasing it when the system is overloaded and decreasing it when the system is underloaded In this way the system load is monitored and adjusted before each frame is generated The degree of stability for the closed loop control system is an important issue The ideal situation is to have a critically damped control system that is
490. raw process at the right time IRIS Performer manages data that is passed to the process callbacks to ensure that the data is frame coherent and isn t corrupted Example 6 3 illustrates the use of a cull process callback Example 6 3 Cull Process Callbacks InitChannels create and configure all channels define callbacks for cull and draw processes pfChanTravFunc chan PFTRAV_CULL CullFunc pfChanTravFunc chan PFTRAV_DRAW DrawFunc The Cull callback Any work that needs to be done in the Cull process should happen in this function ay void CullFunc pfChannel chan void data static long first 1 Lock down whatever processor the cull is using when the cull callback is first called ad if first if pfGetMultiprocess amp PFMP_FORK_CULL amp amp ViewState gt procLock amp PFMP_FORK_CULL pfuLockDownCull pfGetChanPipe chan first 0 User defined pre cull processing Application specific cull knowledge might be used to provide things like line of sight culling aA PreCull chan data 175 Chapter 6 Database Traversal 176 standard Performer culling to the viewing frustum pfCull User defined post cull processing this routine might be used to do things like record cull state from this cull to be used in future culls x7 PostCull chan data The draw function callback I O with IRIS GL devices must
491. raw stages must be separate processes PFMP_FORK_DRAW must be true In this mode the two stages communicate in the classic producer consumer model by way of a pfDispList that is configured as a ring FIFO buffer the cull process puts commands on the ring while the draw process simultaneously consumes these commands The main benefit of using PFMP_CULLoDRAW is reduced latency since the number of pipeline stages is reduced by one and the resulting latency is reduced by an entire frame time The main drawback is that the draw process must wait for the cull process to begin filling the ring buffer Forcing Display List Generation When the cull and draw stages are in separate processes they communicate through a pfDispList the cull process generates the display list and the draw process traverses and renders it The display list is configured as a ring buffer when using PFMP_CULLoDRAW mode as described in the Cull Overlap Draw Mode section However when the cull and draw stages are in the same process as occurs with the PFMP_APPCULLDRAW or PFMP_APP_CULLDRAW multiprocessing models a display list isn t required and by default one will not be used Leaving out the pfDispList eliminates overhead When no display list is used the cull trigger function pfCull has no effect the cull traversal takes place when the draw trigger function pfDraw is invoked In some cases you may want an intermediate pfDispList between the cull and
492. rawn geometry In libpr there are three methods of setting state e immediate mode e display list mode e pfGeoState mode Like the graphics libraries libpr supports the notion of both immediate and display list modes In immediate mode graphics mode changes are sent directly to the Geometry Pipeline i e they have immediate effect In display list mode graphics mode changes are captured by the currently active pfDispList which can be drawn later libpr display lists differ from graphics library objects because they capture only libpr commands and are reusable libpr display lists are useful for multiprocessing applications in 333 Chapter 10 libpr Basics 334 which one process builds up the list of visible geometry and another process draws it Display Lists on page 355 describes libpr display lists A pfGeoState is a structure that encapsulates all the graphics modes and attributes that libpr manages You can individually set the state elements of a pfGeoState to define a graphics context The act of applying a pfGeoState with pfApplyGState configures the state of the Geometry Pipeline according to the modes values and attributes set in the pfGeoState For example the following code fragment shows equivalent ways except for some inheritance properties of pfGeoStates described later of setting up some lighting parameters suitable for a glass surface Immediate mode state specification pfMaterial shin
493. re Performer data mobrect tri 1 788180 1 000870 0 135214 0 076169 0 085488 0 993423 1 574000 0 925908 0 146652 0 089015 0 086072 0 992304 1 793360 0 634711 0 099409 0 076402 0 111845 0 990784 0 836848 0 595230 0 197960 0 156677 0 044503 0 986647 0 709638 0 345676 0 210010 0 157642 0 021968 0 987252 0 581200 0 535321 0 234807 0 145068 0 030985 0 988936 pfdLoadFile uses the function pfdLoadFile_tri to load tri format files into IRIS Performer run time data structures UNC Walkthrough Format The unc format was once used at the University of North Carolina as a format for geometric data in an architectural walkthrough application The loader was developed based on inspection of a few sample files The IRIS Performer unc loader is in the usr share Performer src lib libpfdb libpfunc directory pfdLoadFile uses the function pfdLoadFile_unc to load UNC format files into IRIS Performer run time data structures Chapter 10 lib pr Basics This chapter discusses the rendering library that forms IRIS Performer s foundation Chapter 10 Overview libpr Basics Earlier chapters of this guide described libpf IRIS Performer s high level visual simulation development library Much of libpf is built on top of libpr the high performance rendering and utility library described in this chapter libpr provides many useful system and hardware oriented utilities as well as a high performance interf
494. re are a couple of suggestions for tuning the cull process The default channel culling mode enables all types of culling If your cull process is your most expensive task you may want to consider doing less culling operations When doing database culling always use view frustum culling PFCULL_VIEW and usually use graphics library mode database sorting PFCULL_SORT and pfGeoSet culling PFCULL_GSET as well pfChanTravMode chan root PFCULL_VIEW PFCULL_GSET PFCULL_SORT A cull limited application might realize a quick gain from turning off pfGeoSet culling If you think your database has few textures and materials you might turn off sorting However if possible it would be better to try improving cull performance by improving database construction Efficient Intersection and Traversals on page 460 discusses optimizing cull traversals in more detail Look at the channel culling statistics for A large amount of the database being traversed by the culling process and being trivially rejected as not being in the viewing frustum This can be improved with better spatial organization of the database A large number of database nodes being non trivially culled This can be improved with better spatial organization and breakup of large pfGeodes and pfGeoSets A surprising number of LODs in their fade state the fade computations can be expensive particularly if channel stress management has been enabled Sp
495. re data might reside Directories are searched in the order given beginning with those specified in PFPATH followed by those specified by pfFilePath For example the following function call tells IRIS Performer to search for data first in the current directory then in the data directory within the current directory and then in data directories one and two levels above the current directory pfFilePath data data data Calls to pfFindFile with the name of the file you want to locate return the complete pathname of the file if the result of the search is successful Simulation Loop After the pipes and channels are configured and the scene is loaded the main simulation loop begins and manages scene updates viewpoint updates scene intersection inquiries and image generation The loop has two principal control calls pfSync and pfFrame 65 Chapter 3 Building a Visual Simulation Application Performance 66 The order of operations is this 1 Call pfSync to put the process to sleep until the next frame boundary This step is typically only used when viewpoint information is being updated from a streaming input device such as a head tracker 2 Perform latency critical operations such as setting the viewpoint or reading positional input output devices 3 Call pfFrame to initiate the next cull traversal 4 Perform any time consuming calculations that are required 5 Return to step 1 Ti
496. re more control over the exact framebuffer configuration of your pfWindow you have several options For pure IRIS GL windows you can make GL framebuffer configuration calls such as RGBsize zbsize and mssize directly You can tell IRIS Performer to not do any window configuration by setting an empty attribute array For X windows you can provide the appropriate framebuffer description for the current GL operation to the pfWindow using pfWinFBConfig X uses visuals to describe available framebuffer configurations You can select the visual for your window and set it on the pfWindow with pfWinFBConfig XVisualInfo pointer with XGetVisualInfo will return a list of all visuals on the system and you can search through them to find the appropriate configuration 369 Chapter 10 libpr Basics 370 libpr also offers utilities for creating framebuffer configurations pfFBConfig independently of a pfWindow pfChooseFBConfig takes an attribute array of tokens from Table 10 20 and will return a pfFBConfig structure that can be used with your pfWindows or with X Windows created outside of libpr such as with Motif You can use pfQuerySys to query particular framebuffer resources in the current hardware configuration and then use pfQueryWin to query your resulting framebuffer configuration There is a special utility for supporting mixed model IRIS GL GLX windows GLX windows use a special attribute array returned by GLX getc
497. read in to an IRIS Performer application Rather unique file readers are constructed for each format to be used IRIS Performer can thus work with data from multiple sources concurrently using a common software interface without needing intermediate translation or conversion steps Because these database importers operate at run time they re able to supply executable functions that extend the regular IRIS Performer processing to whatever is required by various formats This eliminates the least common denominator limitation where database constructs that can t be represented in the common format must be either deleted or reconstructed Such limitations are often encountered when all data must be converted to a fixed Exploring Code Exploring Code shared file format In the IRIS Performer paradigm each importer can provide new functions to support the required features that aren t present in IRIS Performer extending full native support for each desired database format To use the visual interface from perfly with your own databases simply list your databases on the perfly command line perfly examines the extension part of each filename to determine what format the file is in File importers are provided as examples with IRIS Performer and supported by perfly for many file formats including 3DStudio 3ds Designer s Workbench dwb Medit Productions medit MultiGen OpenFlight flt SGI BIN and SGO
498. reated upon demand For pure IRIS GL alternate configuration windows must have their graphics context be the same as the base window The rest of this section assumes the use of X windows in either GLX or OpenGL X An alternate configuration window is created as a full pfWindow and is an alternate configuration window by virtue of being given to a base window in a pfList of alternate configuration windows or being directly assigned as one of the standard alternate configuration windows with either of pfWinOverlayWin or pfWinStatsWin A pfWindow may be an alternate configuration window of only one base window at a time alternate configuration windows may not be instanced between base windows The sharing of window attributes between alternate configuration windows such as the parent X window and GL objects for OpenGL windows must be set with pfWinShare on the base window and applied to the alternate configuration windows with pfAttachWin You select the desired alternate configuration window to draw into with pfWinIndex and provide an index into your alternate configuration window list or one of the standard indices PFWIN_GFX_WIN PFWIN_OVERLAY_WIN or PFWIN_STATS_WIN PFWIN_GFX_WIN is the default window index and selects the base window If the alternate configuration window has not been opened it will be opened automatically upon being selected for rendering Example 10 9 demonstrates creating a pfWindow using the default overlay w
499. red when drawing occurs in multiple windows on a single graphics pipeline graphics state elements Individual libpr state components such as material color line stipple pattern point size current texture definition and the other elements that comprise the graphics context heading In the context of X axis to the right Y axis forward and Z axis up then heading is rotation about the Z axis This is the disturbing rotation that pivots your car clockwise or counterclockwise during a skid Heading is also known as yaw but IRIS Performer uses the term heading to keep the H P and R abbreviations distinct from X Y and Z Also see Euler angles heap The process heap is the normal area from which memory is allocated by malloc when more memory is required sbrk is automatically called to increase the process virtual memory Also see arena identity matrix A square matrix with ones down the main diagonal and zeroes everywhere else This matrix is the multiplicative identity in matrix multiplication immediate mode rendering Immediate mode rendering operations are those which immediately issue rendering commands and transfer data directly to the graphics hardware rather than compiling commands and data into data structures such as display lists See compiled mode instancing An object in the scene is called instanced if there is more than one path through the scene graph that reaches it Instancing is most commonly used
500. results may be unexpected No such trickery is required when using the C API so full type checking is always available at compile time pfObjects and the Class Hierarchy Inheritance Graph The relations between classes can be arranged in a directed acyclic inheritance graph in which each child inherits all of its parent s attributes as illustrated in Figure 2 3 IRIS Performer does not use multiple inheritance so each class has only one parent in the graph Note It s important to remember that an inheritance graph is different from ascene graph The inheritance graph shows the inheritance of data elements and member functions among user defined data types the scene graph shows the relationship among instances of nodes in a hierarchical scene definition 43 Chapter 2 IRIS Performer Basics Some classes found in ibpf Some classes found in ibpr Figure 2 3 Partial Inheritance Graph of IRIS Performer Data Types 44 pfObjects and the Class Hierarchy IRIS Performer objects are divided into two groups those found in the libpf library and those found in the libpr library These two groups of objects have some common attributes but also differ in some respects While IRIS Performer only uses single inheritance some objects encapsulate others hiding the encapsulated object but also providing a functional interface that mimics its original one For example a pfChannel has a pfFrustum a pfFrameStats has
501. rformer s primary method of managing system load Table 7 1 shows the IRIS Performer functions for controlling frame processing Table 7 1 Frame Control Functions Function Description pfFrameRate Set the desired frame rate pfSync Synchronize processing to frame boundaries pfFrame Initiate frame processing pfPhase Control frame boundaries pfChanStressFilter Control how stress is applied to LOD ranges pfChanStress Manually control the stress value 193 Chapter 7 Frame and Load Control Table 7 1 continued Frame Control Functions Function Description pfGetChanLoad Determine the current system load pfChanLODAttr Control how LOD is performed including global LOD adjustment and blending fade Figure 7 1 shows a frame timing diagram that illustrates what occurs when frame computations are not completed within the required interval The solid vertical lines in Figure 7 1 represent frame display intervals The dashed vertical lines represent video refresh intervals Refresh count modulo three Video refresh interval Frame display interval Time in seconds ________ rr e 1 60TH lt 1 20TH gt Figure 7 1 Frame Rate and Phase Control In this example the video scan rate is 60 Hz and the frame rate is 20 Hz With the video hardware running at 60 Hz each of the 20 Hz frames should be scanned to the video display three times and the system should wait for every third ve
502. rformer is designed to run at the fixed frame rate as specified by pfFrameRate Selecting a fixed frame rate does not in itself guarantee that each frame can be completed within the desired time It is possible that some frames might require more computation time than is allotted by the frame rate By taking too long these frames cause dropped or skipped frames A situation in which frames are dropped is called an overload or overrun situation A system that is close to dropping frames is said to be in stress Achieving the Frame Rate The first step towards achieving a frame rate is to make sure that the scene can be processed in less than a frame s time hopefully much less than a frame s time Although minimizing the processing time of a frame is a huge effort rife with tricks and black magic certain techniques stand out as IRIS Performer s main weapons against slothful performance e Multiprocessing The use of multiple processes on multi CPU systems can drastically increase throughput e View culling By trivially rejecting portions of the database outside the viewing volume performance can be increased by orders of magnitude e State sorting Many graphics pipelines are sensitive to graphics mode changes Sorting a scene by graphics state greatly reduces mode changes increasing the efficiency of the hardware e Level of detail Objects that are far away project to a relatively small area of the display so fewer polygons can
503. rmation matrix The pfDCS transforms each child C i to C i Scale Rotation Translation Table 5 3 lists functions for manipulating a pfDCS including rotating scaling and translating the children of the pfDCS Table 5 3 DCS Transformations Function Name Description pfNewDCS Create a new pfDCS node pfDCSTrans Set the translation coordinates to x y Z pfDCSRot Set the rotation transformation to h p r pfDCSCoord Rotate and translate by coord pfDCSScale Scale by a uniform scale factor pfDCSMat Use a matrix for transformations pfGetDCSMat Retrieve the current matrix for a given pfDCS pfSwitch Nodes A pfSwitch is a branch node that selects one all or none of its children Use pfNewSwitch to return a handle to a new pfSwitch To select all the children use the PFSWITCH_ON argument to pfSwitchVal Deselect all the children turning the switch off using PPSWITCH_OFF To select a single child give the index of the child from the child list To find out the current value of a given switch call pfGetSwitchVal Example 5 5 in the pfSequence Nodes section illustrates a use of pfSwitch nodes to control pfSequence nodes 127 Chapter 5 Nodes and Node Types 128 pfSequence Nodes A pfSequence is a pfGroup that sequences through a range of its children drawing each child for a specified duration Each child in a sequence can be thought of as a frame in an animation A sequence can consist of any numb
504. rmly distributed within the range 0 2 to 0 7 that is consistent for each polygon with the same number of vertices within a single polyhedron 297 Chapter 9 Importing Databases 298 Silicon Graphics PTU Format The PTU format is named for the IRIS Performer Terrain Utilities of which the pfdLoadFile_ptu function is the sole example at the present time This function accepts as input the name of a control file the file with the ptu filename extension that defines the desired terrain parameters and references additional data files The database shown in Figure 9 11 represents a portion of the Yellowstone National Park This terrain database was generated completely by the IRIS Performer Terrain Utility data generator from digital terrain elevation data and satellite photographic images Image manipulation is performed using the Silicon Graphics ImageVision Library functions H Sn l il WW Pa a FES VN DON V y a A Figure 9 11 Terrain Database Generated by PTU Tools The PTU control file has a fixed format that doesn t use keywords The contents of this file are simply ASCII values representing the following data items Description of Supported Formats The name to be assigned to the top level pfNode built by pfdLoadFile_ptu The number of desired levels of detail LOD for the resulting terrain surface The pfdLoadFile_ptu function will construct this many versions of the t
505. rocessing and rendering system The visual database has at its root a pfScene as described in Chapter 5 and Chapter 6 A pfScene is viewed by a pfChannel which is rendered to a pfPipeWindow by a pfPipe This chapter describes how to use pfPipes pfPipeWindows and pfChannels This section describes rendering pipelines pfPipes and their implementation in IRIS Performer Each rendering pipeline draws into one or more windows pfPipeWindows associated with a single Geometry Pipeline A minimum of one rendering pipeline is required although it is possible to have more than one The Functional Stages of a Pipeline This rendering pipeline comprises three primary functional stages APP Simulation processing which includes reading input from control devices simulating the vehicle dynamics of moving models updating the visual database and interacting with other networked simulation stations CULL Traverses the visual database and determines which portions of it are potentially visible a procedure known as culling selects a level of detail for each model sorts objects and optimizes state management and generates a display list for the draw function DRAW Traverses the display list and issues graphics library commands to a Geometry Pipeline in order to create an image for subsequent display 73 Chapter 4 Setting Up the Display Environment 74 Figure 4 1 shows the process flow for a single pipe system The application con
506. roll ROTx pitch ROTz heading where ROTa angle is a rotation matrix about axis a of angle degrees 95 Chapter 4 Setting Up the Display Environment 96 Angles have not only a degree value but also a sense or indicating whether the direction of rotation is clockwise or counterclockwise Because different systems follow different conventions it is very important to understand the sense of the Euler angles as they are defined by IRIS Performer IRIS Performer follows the right hand rule According to the right hand rule counterclockwise rotations are positive This means that a rotation about the x axis by 90 degrees shifts the Y axis to the Z axis a rotation about the y axis by 90 degrees shifts the Z axis to the X axis and a rotation about the z axis by 90 degrees shifts the X axis to the Y axis Figure 4 4 shows a toy plane somewhat reminiscent of the Ryan S T at the origin of a coordinate system with the angles of rotation labeled for heading pitch and roll The arrows show the direction of positive rotation for each angle Heading Pitch Figure 4 4 Heading Pitch and Roll Angles A roll motion tips the wings from side to side A pitch motion tips the nose up or down A yaw motion steers the plane changing its heading Accurate readings of these angles are critical information for a pilot during a flight and a thorough understanding of how the angles function together is require
507. rs appear when you run ps 1 it 387 Chapter 10 libpr Basics 388 doesn t consume any substantial resources since swap or file system space isn t actually allocated until accessed that is until pfMalloc is called Because IRIS Performer cannot increase the size of the arena after initialization an application requiring a larger shared memory arena should call pfSharedArenaSize to specify the maximum amount of memory to be used Arena sizes as large as 1 7 GB are usually acceptable but you may need to set the virtual memory use and memory use limits using the shell limit command or setrlimit to allow your application to use that much memory Allocating Locks and Semaphores An application requiring lockable pieces of memory should consider using pfDataPools described below Alternatively when a lock or semaphore is required in an application that has called pfInitArenas you can call pfGetSemaArena to get an arena pointer and you can allocate locks or semaphores using usnewlock and usnewsema Datapools Datapools or pfDataPools are also a form of shared memory but they work differently from pfMalloc Datapools allow unrelated processes to share memory and lock out access to eliminate data contention They also provide a way for one process to access memory allocated by another process Any process can create a datapool by calling pfCreateDPool with a name and byte size for the pool If an unrelate
508. rsection Query Token Names Query Token Description PFOQHIT_FLAGS Status and validity information PFQHIT_SEGNUM Index of the segment in pfSegSet request PFQHIT_SEG Line segment as currently clipped PFQHIT_POINT Intersection point in object coordinates Intersection Traversal Table 6 3 continued Intersection Query Token Names Query Token Description PFQHIT_NORM Geometric normal of an intersected triangle PFQHIT_VERTS Vertices of an intersected triangle PFQHIT_TRI Index of an intersected triangle PFOQHIT_PRIM Index of an intersected primitive in pfGeoSet PFQHIT_GSET pfGeoSet of an intersection PFQHIT_NODE pfGeode of an intersection PFQHIT_NAME Name of pfGeode PFQHIT_XFORM Current transformation matrix PFQHIT_PATH Path in scene graph of intersection The PFQHIT_FLAGS field is bit vector with bits that indicate whether an intersection occurred and whether the point normal primitive and transformation information is valid For some types of intersections only some of the information has meaning for instance for a pfSegSet bounding volume intersecting a pfNode bounding sphere the point information may not be valid Queries can be performed singly by calling pfQueryHit with a single query token or several at a time by using pfMQueryHit with an array of tokens In the latter case the return information is placed in the specified order into a return array Intersection Masks Before using pfNodelIsectSegs to interse
509. rther details Horizontal FOV Top Vertical FOV Right Eyepoint y tan vertical FOV 2 x tan horizontal FOV 2 Aspect Ratio Figure 4 3 Symmetric Viewing Frustum The viewing frustum is called symmetric when the vertical half angles are equal and the horizontal half angles are equal Field of View The FOV is the angular width of view Use pfChanFO V chan horiz vert to set up viewing angles in IRIS Performer The quantities horiz and vert are the total horizontal and vertical fields of view in degrees usually you specify one and let IRIS Performer compute the other If you re specifying one angle pass any amount less than or equal to zero or greater than or equal to 180 as the other angle IRIS Performer automatically computes the unspecified FOV angle to fit the pfChannel viewport using the aspect ratio preserving relationship tan vert 2 tan horiz 2 aspect ratio Using Channels That is the ratio of the tangents of the vertical and horizontal half angles is equal to the aspect ratio For example if horiz is 45 degrees and the channel viewport is twice as wide as it is high so the aspect ratio is 0 5 then the vertical field of view angle vert is computed to be 23 4018 degrees If both angles are unspecified pfChanFOV assumes a default value of 45 degrees for horiz and computes the value of vert as described Clipping Planes Clipping planes define the near and far boundaries of t
510. rtical retrace signal before displaying the next image The numbers across the top of the figure represent the refresh count modulo three New images are displayed on refreshes whose count modulo three is zero as shown by the solid lines 194 Frame Rate Management In the first frame of this example the new image isn t yet completed when the third vertical retrace signal occurs the same image must therefore be displayed again during the next interval This situation is known as frame overrun because the frame computation time extends past a refresh boundary Frame Synchronization Because of the overrun the frame and refresh interval timing is no longer synchronized it s out of phase A decision must be made either to display the same image for the remaining two intervals or to switch to the next image even though the refresh isn t aligned on a frame boundary The frame rate control mode discussed in the next section determines which choice is selected Knowing that the situation illustrated in Figure 7 1 is a possibility you can specify a frame control mode to indicate what you would like the system to do when a frame overrun occurs To specify a method of frame rate control call pfPhase There are three available choices e Free run without phase control PFPHASE_FREE_RUN tells the application to run as fast as possible to display each new frame as soon as it s ready without attempting to maintain a constant
511. ry organized for efficiency e pfMorph Combines morphs attributes like color coordinates Geometric Nodes e pfGeode Geometry node e pfBillboard Geometry that rotates to face the viewpoint Overview of the IRIS Performer Libraries e pfLightPoint Luminescent light points e pfText Geometry based upon pfFont and pfString e pfLightSource User manipulatable lights which support high quality spotlights and shadows A visual database is a graph of nodes that is rooted by a pfScene A pfScene is viewed by a pfChannel which in turn is culled and drawn by a pfPipe Scenes are typically but not necessarily constructed by the application at database loading time IRIS Performer supplies sample source code that shows how to construct a scene from several popular database formats see Chapter 9 for more information IRIS Performer provides traversal functions that act on a pfScene or portions thereof These functions include e comprehensive user directed intersections e flattening modeling transformations for improved cull intersection and rendering performance e cloning a database subgraph to obtain model instancing which shares geometry but not articulations e deletion of scene graph components e printing for debugging purposes The application can direct and customize traversals through the use of identification masks on a per node basis and through the use of function callbacks Frame Control IRIS Performer is d
512. ry source of published visual simulation experience In the past this conference has been known as the National Training Equipment Center Industry Conference NTEC IC and the Interservice Industry Training Equipment Conference I ITEC Proceedings are available from the National Technical Information Service NTIS Here are NTIS order numbers for several of the older proceedings e Seventh N IC November 1974 AD A000 970 NTEC e Eighth N IC November 1975 AD A028 885 NTEC e Ninth N IC November 1976 AD A031 447 NTEC e Tenth N IC November 1977 AD A047 905 NTEC e Eleventh N IC November 1978 AD A061 381 NTEC e First I ITEC November 1979 AD A077 656 NTEC e Third I ITEC November 1981 AD A109 443 NTEC xxxiii About This Guide XXXiV The IMAGE Society is dedicated solely to the advancement of visual simulation technology and its applications It holds conferences and workshops the proceedings of which are an excellent source of advice and guidance for visual simulation developers The society can be reached through electronic mail at image acvax inre asu edu Some of the IMAGE proceedings published by the Air Force Human Resources Lab AFHRL at Williams AFB prior to the formation of the IMAGE Society are also available from the NTIS Order numbers are e IMAGE May 1977 AD A044 582 AFHRL e IMAGE II closing July 1981 AD A104 676 AFHRL e IMAGE II proceedings November 1981 AD A110 226 AFHRL The Society of Photo Opti
513. s a full frame period for the application process while culling and drawing share this same interval This mode is appropriate when the host s simulation tasks are extensive but graphic demands are light as might be the case when complex vehicle dynamics are performed but only a simple dashboard gauge is drawn to indicate the results Combine the application and cull stages in a process that is separate from the draw process This mode is appropriate for many simulation applications when application and culling demands are light It allocates a full CPU for drawing and has the APP and CULL stages share a frame period Like the PFMP_APP_CULLDRAW mode this mode has a single frame period of pre draw latency Perform the application cull and draw stages as separate processes This is the full maximum throughput multiprocessing mode of IRIS Performer operation In this mode each pipeline stage is allotted a full frame period for its processing Two frame periods of latency exist when using this high degree of parallelism You can also use pfMultiprocess to specify the method of communication between the cull and draw stages using the bitmasks PFMP_CULLoDRAW and PFMP_CULL_DL_DRAW 215 Chapter 7 Frame and Load Control 216 Cull Overlap Draw Mode Setting PFMP_CULLoDRAW specifies that the cull and draw processes for a given frame should overlap that is that they should run concurrently For this to work the cull and d
514. s can be made af pfPipe p pfGetPipe pipe pfNotify PFNFY_INFO PFNFY_PRINT Initializing stage 0x x of pipe d stage pipe Using pfPipeWindows Using pfPipeWindows IRIS Performer can automatically create and open a full screen window with a default configuration for your pfPipe At the other extreme you can create and configure your own windows and set them on a pfPipe Your window may be pure IRIS GL IRIS GLX also known as mixed model or OpenGL X In all cases the pfPipeWindow is the mechanism by which a pfPipe knows about and keeps track of the windows to which it is to render For all window types there is a single interface for creating configuring and managing the windows In the simplest case IRIS Performer will automatically create a pfPipeWindow for the application and automatically open a full screen window upon the first call to pfFrame This trivial case is demonstrated in Example 4 1 Creating Configuring and Opening pfPipeWindow In most cases there are some window parameters such as size and origin that you will want to set You may also have custom graphics state that you need to set to fully initialize your rendering window This section describes the basics for setting up windows through the pfPipeWindow mechanism Rendering to the pfPipeWindow is done through a pfChannel s draw process callback and is discussed in the next section in Creating and Configuring a pfChannel
515. s greater accuracy at that level Provides the pfPartition node type to partition geometry for fast intersection testing Use a pfPartition node as the parent for anything that needs intersection testing Provides level of detail LOD capabilities in order to draw simpler and thus cheaper versions of objects when they re too far away for the user to discern small details Allows intersection performance enhancement via precomputation of polygon plane equations within pfGeoSets This pre computation is in the form of a traversal that is nearly always appropriate only in cases of non intersectable or dynamically changing geometry might these cached plane equations be disadvantageous This optimization is 451 Chapter 13 Performance Tuning and Debugging 452 performed by pfuCollideSetup using the PFTRAV_IS_CACHE bit mask value Sorts pfGeoSets by graphics state in the cull process in order to minimize state changes and flatten matrix transformations when libpf creates display lists to send to the draw process as occurs in the PFMP_CULL_DL_DRAW multiprocessing mode This procedure takes extra time in the cull stage but can greatly improve performance when rendering a complex scene that uses many pfGeoStates The sorting is enabled by default it can be turned off and on by calling the function pfChanTravMode chan PFTRAV_CULL mode and including or excluding the PRCULL_SORT token See pfChannel Traversal Modes in C
516. s operation for example if you delete an object that another object still references Reference counting provides a bookkeeping mechanism that makes object deletion safe an object is never deleted if its reference count is greater than zero Only libpr objects have an explicit reference count In libpf pfNodes are reference counted by their parents in the scene graph and all other libpf objects such as pfChannels and pfPipes have no reference count because you cannot currently delete them All libpr objects such as pfGeoState and pfMaterial have a reference count that specifies how many other objects refer to it A reference is made whenever an object is attached to another using the IRIS Performer routines shown in Table 2 2 Table 2 2 Routines that Modify libpr Object Reference Counts Routine Action pfGSetGState Attaches a pfGeoState to a pfGeoSet pfGStateAttr Attaches a state structure such as a pfMaterial to a pfGeoState pfGSetHlight Attaches a pfHighlight to a pfGeoSet pfTexDetail Attaches a detail pfTexture to a base pfTexture pfGSetAttr Attaches attribute and index arrays to a pfGeoSet pflexImage Attaches an image array to a pfTexture pfAddGSet pfReplaceGSet Modify pfGeoSet pfGeode association pfInsertGSet pfObjects and the Class Hierarchy When object A is attached to object B the reference count of A is incremented Additionally if A replaces a previously referenced object C then the reference count
517. s per second and the time extent of a frame is 16 7ms The ability to fit all processing within a frame depends on several variables some of which are e the number of pixels being filled e the number of transformations and modal changes being made e the amount of processing required to create a display list for a single frame e the quantity of information being sent to the graphics subsystem Through intelligent management of Silicon Graphics CPU and graphics hardware IRIS Performer minimizes the above variables in order to achieve the desired frame rate However in some cases peak frame rate is less important than a fixed frame rate Fixed frame rate means that the display is updated at a consistent unvarying rate While a simple step towards achieving a fixed frame rate is to reduce the frame rate expectation we shall explore other less Draconian mechanisms in this chapter that do not adversely impact frame rates As discussed in the following sections IRIS Performer lets you select the frame rate and has built in functionality to maintain that frame rate and control overload situations when the draw time exceeds or grows 191 Chapter 7 Frame and Load Control uncomfortably close to a frame time While these methods can be effective they do require some cooperation from the run time database In particular databases should be modeled with levels of detail and be spatially arranged Selecting the Frame Rate IRIS Pe
518. s provided as sample source code These examples show how to import more than thirty popular database formats and how to export scene graphs in the open Designer s Workbench and Medit formats see Chapter 9 for more information 15 Chapter 2 IRIS Performer Basics 16 This guide describes IRIS Performer in a top down fashion Chapters 3 through 8 describe libpf the visual simulation application development library Chapters 10 and 11 describe libpr the high performance rendering library Chapter 9 discusses libpfdu the database utility library and libpfdb the format specific collection of file load convert and store utilities Applications IRIS Performer can be used in a variety of ways You can use it as a complete database processing and rendering system for applications such as flight simulation driver training or virtual reality It can also be used in conjunction with layered application development tools to perform the low level portion of the visual simulation development projects In short applications can use part or all of the features provided by IRIS Performer For example consider a driver training application that has already been developed This application consists of a database simulation code and rendering code The application can be ported to IRIS Performer in several ways If time is short and the bottleneck is in the rendering code IRIS Performer s libpr library layer can take over the rendering ta
519. s reference to a later section where you can learn more about the topic It takes only a few lines of code to set up an IRIS Performer libpf application Furthermore once you have an application framework that you like you can use it again to create other libpf applications Certain configuration and control routines are required in all applications while others depend on the features needed and the platform for which the application is designed The basic requirements for simple programs are the same as for more complex programs so you can learn the basic structure from a very simple framework application and then build on it to suit your needs Take a few moments to browse through the introductory program simple c shown in Example 3 1 If you want to compile this program refer to the section of this chapter titled Compiling and Linking IRIS Performer Applications Note Sample code built upon the framework presented in simple c is presented throughout the remainder of this guide so familiarize yourself with the concepts presented here before moving on to more advanced subjects 55 Chapter 3 Building a Visual Simulation Application 56 Example 3 1 shows the basic framework of an IRIS Performer application Example 3 1 Structure of an IRIS Performer Application include lt stdlib h gt include lt Performer pf h gt include lt Performer pfutil h gt include lt Performer pfdu h gt int main int argc ch
520. s the intersection of one or more line segments with the database The intersection traversal is user directed Intersections are used to determine e height above terrain e line of sight visibility e collisions with database objects 153 Chapter 6 Database Traversal 154 Like other traversals intersection traversals can be directed by the application through identification masks and function callbacks Table 6 1 lists the routines and data types relevant to each of the major traversals more information about the listed traversal attributes can be found later in this chapter and in the appropriate reference pages Table 6 1 Traversal Attributes for the Major Traversals Traversal Application Cull Draw Intersection f PFTRAV_APP PFTRAV_CULL PFTRAV_DRAW PFTRAV_ISECT Attribute Controllers pfChannel pfChannel pfChannel pfSegSet Global pfFrame pfFrame pfFrame pfFrame Activation pfSync pfNodelsect fAppFrame Segs pfChan Pree 0 NodelsectSegs Global pfChanTrav pfChanTrav pfChanTrav pfIsectFunc Callbacks Func Func Func Activation pfApp pfCull pfDraw pfFrame within pfNodelsect Callback Segs pfChan NodelsectSegs Path NA pfCullPath NA NA Activation Modes pfChanTrav pfChanTrav pfChanTrav pfSegSet also Mode Mode Mode discriminator callback Node pfNodeTrav pfNodeTrav pfNodeTrav pfNodeTrav Callbacks Funcs Funcs Funcs Funcs Traverser pfChanTrav pfChanTrav pfChanTrav pfS
521. s to pfGeoSets is an important point in the database structure If there are many very small pfGeoSets within a single pfGeode not culling down to pfGeoSets can actually improve overall frame time because the cost of drawing the tiny pfGeoSets may be small relative to the time spent culling them Adding more pfGeodes to break up the pfGeoSets can help by providing a slightly more accurate cull at less cost than considering each pfGeoSet individually In addition pfGeodes are culled by their bounding spheres which is faster than the culling of pfGeoSets which are culled by their bounding boxes The size both spatial extend and number of triangles can also directly impact culling and drawing performance If pfGeoSets are relatively large there will be fewer to cull so pfGeoSet culling can probably be afforded pfGeoSets with more triangles will draw faster However pfGeoSets with larger spatial extent are more likely to have geometry that is being drawn that is outside of the viewing frustum which wastes time in the graphics stage Breaking up some of the large pfGeoSets can improve graphics performance by allowing a more accurate cull 463 Chapter 13 Performance Tuning and Debugging 464 With some added cost to the culling task the use of Level of Detail nodes pfLODs can make a tremendous difference in graphics performance and image quality LODs allow objects to be automatically drawn with a simplified version when they are in a s
522. s when textures are encountered for the first time while drawing the database and must then be downloaded to texture memory Utilities are provided in libpfutil to apply textures appropriately see the pfuDownloadTexList routine in the distributed source code file usr share Performer src libflibpfutil tex c The perfly application demonstrates this see the perfly source file generic c in either the C language usr share Performer src sample C common or C language usr share Performer src sample C common versions of perfly Minimize the use of pfSCSs and pfDCSs and nodes with draw callbacks in the database since aggressive state sorting is kept local to subtrees under these nodes 459 Chapter 13 Performance Tuning and Debugging Don t do any graphics library input handling in the draw process Instead use X input handling in an asynchronous process IRIS Performer provides utilities for asynchronous input handling in libpfutil with source code provided in usr share Performer src lib libpfutil input c For a demonstration of asynchronous X input handling see provided sample applications such as perfly and also the distributed sample programs usr share Performer src pguide libpf C motif c and usr share Performer src pguide libpfui C motifxformer c Efficient Intersection and Traversals Here are some tips on optimizing intersections and traversals 460 Use pfPartition nodes on pieces of the database that will be hand
523. sample perfly C keybd c contains a list of these key sequences and their effects Remember that you can always use the lt Esc gt key to terminate perfly at any time The control panel s field of view slider can be used to select a wide angle view up to 100 degrees As you travel through the building try turning on the fog effect by clicking the Fog button Experiment with the fog density and other controls Remember If you ve closed the control panel the lt F1 gt key will restore it Flying The Fly motion model provides an alternative to Drive This model allows full motion in three dimensions unlike the Drive model which doesn t allow vertical motion The mouse in the Fly model is used in much the same way to control motion but when steering the vertical position of the mouse Exploring the IRIS Performer Sample Scenes in the window controls your vertical tilt You can select this mode by pressing the right mouse button on the button marked Drive and select Fly from the menu As when driving the left button makes you go forward and the right button makes you go backward As long as either button is pressed you ll continue to accelerate You turn holding the middle mouse button down and moving the cursor away from the center of the simulation window Moving the cursor left or right causes left and right turns respectively Moving the cursor up or down causes the view direction to tilt up or down respe
524. se it s important to know when the number of polygons becomes a limiting factor To turn wireframe mode off just click the Style button or press w again The w key can be used to cycle through several different draw styles To close the entire control panel and devote the entire screen to the model click the GUI Off button at the upper right of the control panel or just press the lt F1 gt key Press the lt F1 gt key again to restore the control panel If you click the Stats button in the control panel a transparent panel showing scene statistics appears overlaid on the screen The buttons next to the Stats button allow you to choose one of the available statistical displays Try moving around in the scene while watching how the statistics change Note in particular that the number of triangles being considered for rendering changes drastically depending on where you look this demonstrates IRIS Performer s use of culling to ignore objects that are completely outside the field of vision For more information about culling see Chapter 6 Database Traversal For more detailed information on the statistics panels see Chapter 12 Statistics Several other keys on the keyboard are active and can be used to control perfly even when the control panel isn t displayed Pressing the key will print a list of most key sequences to the shell window For full details the file usr share Performer src
525. se pfQueryFeature with a feature specifier value of PFOQFTR_LMODEL_ATTENUATION or PFOFTR_LIGHT_ATTENUATION to find out which is supported in the current run time environment Note Jibpf applications can include light sources in a scene graph with the pfLightSource node Materials IRIS Performer materials are an extension of graphics library materials see Imdef 3g for IRIS GL or glMaterial for OpenGL pfMaterials encapsulate the ambient diffuse specular and emissive colors of an object as well as its shininess and transparency A pfMaterial is created by calling pfNewMtl As with any of the other attributes a pfMaterial can be referenced in a pfGeoState captured by a display list or invoked as an immediate mode command pfMaterials by default allow object colors to set the ambient and diffuse colors This allows the same pfMaterial to be used for objects of different colors removing the need for material changes and thus improving performance This mode can be changed with pfMtlColorMode mtl side PFMTL_CMODE IRIS GL only supports the front material tracking the current color while OpenGL allows front or back materials to track the current color If the same material is used for both front and back materials there is no difference in functionality Color Tables A pfColortable substitutes its own color array for the normal color attribute array PFGS_COLOR amp 4 of a pfGeoSet This allows the same geometry to appear
526. sed and fundamental concepts for working with its basic building blocks the functions of the low level library libpr that gives IRIS Performer its speed Chapter 11 Math Routines details the comprehensive math support provided as part of IRIS Performer Chapter 12 Statistics discusses the various kinds of statistics you can collect and display about the performance of your application xxvii About This Guide xxviii e Chapter 13 Performance Tuning and Debugging explains how to use performance measurement and debugging tools and provides hints for getting maximum performance e Chapter 14 Programming with C discusses the differences between using the C and C programming interfaces e Appendix A Image Gallery contains some sample images created by using IRIS Performer to display various scene databases Conventions This guide uses the following typographical conventions Bold is used for function names with parentheses appended to the name Also bold lowercase letters represent vectors and bold uppercase letters denote matrices Italics indicates filenames IRIX command names command line option flags variables and book titles Fixed width is used for code examples and system output Bold Fixed width indicates user input items that you should type in from the keyboard Note that in some cases it s convenient to refer to a group of similarly named IRIS Performer fun
527. set the viewpoint field of view FOV and near and far clipping planes based on the size of the scene pfChanScene chan scene pfChanFOV chan 45 0f 0 0f pfGetNodeBSphere root amp bsphere pfChanNearFar chan 1 0f 10 0f bsphere radius When you pass in zero as a field of view in this case the vertical FOV IRIS Performer matches the FOV to the aspect ratio of the channel Setting Up the Basic Elements 13 Render the scene repeatedly until the specified time is up a Set up the viewpoint for the next frame pfChanView chan view xyz view hpr a Initiate the next cull draw cycle to render the frame pfFrame 14 When the time is up exit IRIS Performer pfExit The remainder of this chapter discusses portions of the outline in detail You may find it helpful to continue to refer to simple c while you read the following sections Setting Up the Basic Elements This section describes how to set up the basic requirements of an IRIS Performer libpf application Using IRIS Performer Header Files The header files for the IRIS Performer libraries are in the usr include Performer directory They include pf h and pr h header files for libpf and libpr respectively irisgl h and opengl h to set up declarations for whichever graphics library your application uses and other header files for use with the other IRIS Performer libraries The header files contain useful macros as well as function
528. sform a frustum pfXformBox Transform and extend a bounding box pfOrthoXformCyl Transform a cylinder pfOrthoXformSphere r Transform a sphere 411 Chapter 11 Math Routines Intersecting Volumes 412 IRIS Performer provides a number of routines that test for intersection with volumes Point Volume Intersection Tests The point volume intersection test returns PFIS_TRUE if the specified point is in the volume and PFIS_FALSE otherwise Table 11 8 lists and describes the routines that test a point for inclusion within a bounding volume Table 11 8 Testing Points for Inclusion in a Bounding Volume Routine Test pfBoxContainsPt Point inside a box pfSphereContainsPt Point inside a sphere pfCylContainsPt Point inside a cylinder pfHalfSpaceContainsPt Point inside a half space pfFrustContainsPt Point inside a frustum Volume Volume Intersection Tests IRIS Performer provides a number of volume volume tests that are used internally for bounding volume tests when culling to a view frustum or when testing a group of line segments against geometry in a scene see Intersecting With pfGeoSets on page 416 You can intersect spheres boxes and cylinders against half spaces and against frustums for culling You can intersect cylinders against spheres for testing grouped segments against bounding volumes in a scene Intersecting Volumes Table 11 9 lists and describes the routines that test for volume intersections
529. should be rewritten for the C API to pass by reference void MyVectorAdd pfVec2 amp dst pfVec2 amp vl pfVec2 amp v2 dst 0 v1 0 v2 0 dst 1 v1 1 v2 1 or void MyVectorAdd pfVec2 dst pfVec2 vl pfVec2 v2 dst gt vec 0 vl gt vec 0 v2 gt vec 0 dst gt vec 1 vl gt vec 1 v2 gt vec 1 Without this change time will be wasted copying v1 and v2 by value and the result will not be returned to the routine calling MyVectorAdd Interface Between C and C API Code The same difference in passing conventions applies if you are calling a C function from code that uses the C API Functions passing typedefed arrays with the C API must have a different prototype for use with the C API Macros for use in C prototypes bilingual can be found in usr include Performer prmath h if PF_CPLUSPLUS_API define PFVEC2 pfVec2 amp define PFVEC3 pfVec3 amp define PFVEC4 pfVec4 amp define PFQUAT pfQuat amp define PFMATRIX pfMatrix amp else define PFVEC2 pfVec2 define PFVEC3 pfVec3 489 Chapter 14 Programming with C Subclassing pfObjects 490 define PFVEC4 pfVec4 define PFQUAT pfQuat define PFMATRIX pfMatrix endif PF_CPLUSPLUS_API These macros are used in the C API prototypes for IRIS Performer that pass typedefed arrays e g extern float pfDotVec2 const PFVEC2 vl const PFVEC2 v2 But they are not necessary o
530. sk with minimal effort Alternatively it may be better to create an importer to import the existing database into IRIS Performer s run time format and gain the extra features that libpf provides Features This section lists the features of the libraries High Performance Rendering Library ibpr Features libpr consists of a number of facilities generally required in most visual simulation and real time graphics applications e High speed geometry rendering functions e Efficient graphics state management e Comprehensive lighting and texturing e Simplified window creation and management What Is IRIS Performer Immediate mode graphics Display list graphics Integrated 2D and 3D text display functions A comprehensive set of math routines Intersection detection and reporting Color table utilities Asynchronous filesystem I O Shared memory allocation facilities High resolution clocks and video interval counters Visual Simulation Application Library ibpf Features Multiple graphics pipeline capability Multiple windows per graphics pipeline Multiple display channels per window Hierarchical scene graph construction and real time editing Multiprocessing parallel simulation intersection cull and draw processes and asynchronous database management System stress and load management Level of detail model switching with fading Rapid culling to the viewing frustum Intersections and database queries Dynamic
531. so see e Akeley Kurt RealityEngine Graphics Computer Graphics Annual Conference Series SIGGRAPH 1993 pp 309 318 e Rohlf John and James Helman IRIS Performer A High Performance Multiprocessing Toolkit for Real Time 3D Graphics Computer Graphics Proceedings Annual Conference Series SIGGRAPH 1994 pp 381 394 e Helman James Sharon Clay Wes Hoffman Eric Johnston Michael Jones Michael Limber and Philippe Tarbouriech Designing Real Time 3D Graphics for Entertainment Course Notes of 1995 SIGGRAPH Course 6 1995 e Shoemake Ken Animating Rotation with Quaternion Curves SIGGRAPH 85 Conference Proceedings Vol 19 Number 3 1985 Xxix About This Guide XXX The IRIS GL and OpenGL Graphics Libraries For information about IRIS GL see these Silicon Graphics publications e Graphics Library Programming Guide Volumes I and II e Graphics Library Programming Tools and Techniques To order all three of the above manuals call 1 800 800 SGI1 in the U S and Canada and specify part number M4 GLGT 5 2 Outside the U S and Canada please contact your local sales office or distributor For information about OpenGL see e Neider Jackie Tom Davis and Mason Woo OpenGL Programming Guide Reading Mass Addison Wesley Publishing Company Inc 1993 A comprehensive guide to learning OpenGL e OpenGL Architecture Review Board OpenGL Reference Manual Reading Mass Addison Wesley Pu
532. ss mode tokens of which each statistics class has its own and which have the form PFSTATS_class_mode and PFFSTATS _class_mode for pfStats and pfFrameStats class modes respectively 437 Chapter 12 Statistics 438 e Statistics query tokens used with pfQueryStats pfMQueryStats pfQueryFStats and pfMQueryFStats These tokens are of the form PFSTATSVAL_ and PFFSTATSVAL_ and have matching pfStatsVal types for holding the returned data The token PFFSTATS_BUF_MASK selects the pfFrameStats statistics buffers Statistics Buffers You can only access the PREV and CUM statistics buffers from the IRIS Performer application process Statistics from desired buffers in other processes should be queried in the application process and then passed down the process pipeline which you can do using the channel data utility The AVG buffer is copied down the process pipeline at the end of each update period and so is available to by queried by other processes The CUR statistics buffer is the current working area and contains the statistics accumulated so far from previous stages current frame the contents of the CUR buffer is very dependent on the multiprocess configuration but is almost always empty in the application process so queries should access the PREV buffer Statistics that are added to the CUR buffer via copying accumulation or immediate mode collection such as with pfStatsCountGSet and pfFStatsCountNode will be prop
533. stem contained within it Nodes A B and C are the leaf geometry nodes they are shared rather than copied 122 Working With Nodes The code in Example 5 3 shows how to create cloned instances Example 5 3 Creating Cloned Instances pfGroup gl g2 p pfDCS d pfGeode a b c Create initial instance of scene hierarchy of p under group gl add a DCS to p then add thr pfGeode nodes under the DCS Wes pfAddchild gl pfAddChild p d pfAddChild d a d b d c 1 p J r r pfAddChild pfAddChild a Create cloned instance version of p under g2 pfAddChild g2 pfClone p 0 Notice that pfGeodes are cloned by instancing rather than copying Also notice that the second argument to pfClone is 0 that argument is currently required by IRIS Performer to be zero ef Bounding Volumes libpf uses bounding volumes for culling and to improve intersection performance libpf computes bounding volumes for all nodes in a database hierarchy unless the bound is explicitly set by the application The bounding volume of a branch node encompasses the spatial extent of all its children libpf automatically recomputes bounds when children are modified By default bounding volumes are dynamic that is libpf automatically recomputes them when children are modified For instance in Example 5 4 when the DCS is rotated nothing more needs to be done to update the bounding volume
534. structs and modifies the scene definition a pfScene associated with a channel The traversal process associated with that channel s pfPipe then traverses the scene graph building an IRIS Performer libpr display list As shown in the figure this display list is used as input to the draw process that performs the actual graphics library actions required to draw the image Application Traversal Cull Draw Frame Buffer Pipeline 0 Figure 4 1 Single Graphics Pipeline IRIS Performer also provides additional processes for application processing tasks such as database loading and intersection traversals but these processes are per application and are asynchronous to the software rendering pipeline s An IRIS Performer application renders images using one or more pfPipes Each pfPipe represents an independent software rendering pipeline Most IRIS systems contain only one Geometry Pipeline so a single pfPipe is usually appropriate This single pipeline is often associated with a window that occupies the entire display surface Alternative configurations include Onyx systems with Reality Engine graphics allowing up to three Geometry Pipelines Applications can render into multiple windows each of which is connected to a single Geometry Pipeline through a pfPipe rendering pipeline Using Pipes Figure 4 2 shows the process flow for a dual pipe system Notice both the differences and similarities between these two figures Ea
535. switch ranges these offsets force IRIS Performer to perform otherwise avoidable square roots calculations in order to correctly calculate the effects of scale and offset on the LOD Level of Detail Range Processing The LOD switch ranges present in LOD nodes are processed before being used to make the level of detail selection The goal of range setting is to switch LODs as objects reach certain levels of perceptibility The size of a channel in pixels the field of view used in viewing and the distance from the observer to the display surface all affect object perceptibility IRIS Performer uses a channel size of 1024x1024 pixels and a 45 degree field of view as the basis for calculating LOD switching ranges The screen space size of a channel and the current field of view are used to compute an LOD scale factor that is updated whenever the channel size or the field of view changes There is an additional global LOD scale factor that can be used to adjust switch ranges based on the relationship between the observer and the display surface The default global scale factor is 1 Note that LOD switch ranges are also effected by LOD states that have been attached to either a particular LOD or to a channel that contains the LOD These LOD states provide the mechanism to apply both a scale and an offset for an LODs switch ranges and to the effect of system stress on those switch ranges See Level of Detail States on page 202 for more informat
536. t The Silicon Graphics Object format is used by several cool utility programs and was one of the first database formats supported by IRIS Performer The image in Figure 9 12 shows a model generated by Paul Haeberli and loaded into perfly by the pfdLoadFile_sgo database importer 303 Chapter 9 Importing Databases 304 aA Figure 9 12 Model in SGO Format Objects in the SGO format have per vertex color specification and multiple data formats Objects contained in SGO files are constructed from three data types e lists of quadrilaterals e lists of triangles e triangle meshes Objects of different types can be included as data within one SGO file The SGO format has the following structure 1 A magic number 0x5424 which identifies the file as an SGO file 2 A set of data for each object Each object definition begins with an identifying token followed by geometric data There can be multiple object definitions in a single file An end of data token terminates the file Description of Supported Formats The layout of an SGO file is lt SGO file magic number gt lt data type token for object 1 gt lt data for object 1 gt lt data type token for object 2 gt lt data for object 2 gt lt data type token for object n gt lt data for object n gt lt end of data token gt Each of the identifying tokens is 4 bytes long Table 9 8 lists the symbol value and meaning for each token Tab
537. t Operating Room Database pfdLoadFile uses the function pfdLoadFile_lsb to load LSB format files into IRIS Performer run time data structures When working with Lightscape Technologies files remember that hardware lighting isn t needed because all illumination effects have already been accounted for with the ambient color at each vertex Medit Productions MEDIT Format The medit format is used by the Medit database modeling system produced by Medit Productions The Performer medit loader is in the usr share Performer srcflibflibpfdb libpfmedit directory pfdLoadFile uses the function pfdLoadFile_medit to load MEDIT format files into IRIS Performer run time data structures 291 Chapter 9 Importing Databases 292 NFF Neutral File Format The nff format was developed by Eric Haines as a way to provide standard procedural databases for evaluating ray tracing software IRIS Performer includes an extended NFF loader with superquadric torus support a named build keyword and numerous small bug fixes The nff loader is located in the usr share Performer src lib libpfdb libpfnff directory The file usr share Performer data sampler nff uses each of the NFF data types It is an excellent way to explore the Show Tree Draw Style and Highlight Mode features of Perfly It is included here LOLs 75 00r 25 46 8 2 08 0 E e220 0 OT 2s 1 build torus cylinder 5 0
538. t ad 1 OFS ate nE e 000E OOT pfPushMatrix pfMultMatrix mat DRAW THE INPUT STRING pfDrawString str pfPopMatrix pfSwapWinBuffers pfGetCurWin 331 Chapter 10 libpr Basics 332 while t lt 2 5f Table 10 5 lists the key routines used to manage pfStrings Table 10 5 pfString Routines Function Description pfNewString Create a new pfString pfDelete Delete a pfString pfStringFont Set the pfFont to use when drawing this pfString pfStringString Set the character array that this pfString will represent render pfDrawString Draw this pfString pfFlattenString Flatten all positional translations and the current specification matrix into individual pfGeoSets so that more memory is used but no matrix transforms or translates have to be done between each character of the pfString pfStringColor Set the color of the pfString pfStringMode Specify a particular mode for this pfString Valid Modes to set PFSTR_JUSTIFY set the line justification and has the following possible values PFSTR_FIRST or PFSTR_LEFT PFSTR_MIDDLE or PFSTR_CENTER and PFSTR_LAST or PFSTR_RIGHT PFSTR_CHAR_ SIZE set the number of bytes per character in the input string and has the following possible values PFSTR_CHAR PFSTR_SHORT PFSTR_INT pfStringMat Specify a transform matrix that will affect the entire character string when the pfString is drawn pfStringSpacing Specify a scale factor fo
539. t d m D M for general none matrices pfInvertAffMat d m D M1 with M none affine pfInvertOrthoMat d m D M1 with M none orthogonal pfInvertOrthoNMat d m D M1 with M none orthonormal 401 Chapter 11 Math Routines 402 Table 11 2 continued Routines for 4x4 Matrices Routine Effect Macro Equivalent pfInvertIdentMat d m D M with M none equal to the identity matrix pfEqualMat d m returns TRUE if PFEQUAL_MAT D M FALSE otherwise pfAlmostEqualMat d m tol returns TRUEifeach PFALMOST_EQUAL_MAT element of D is within tol of the corresponding element of M FALSE otherwise Some of the math routines that take a matrix as an argument are restricted to affine orthogonal or orthonormal matrices these restrictions being noted by Aff Ortho and OrthoN respectively If such a restriction isn t noted in a libpr routine name the routine can take a general matrix An affine transformation is one that leaves the homogeneous coordinate unchanged that is in which the last column is 0 0 0 1 An orthogonal transformation is one that preserves angles It can include translation rotation and uniform scaling but no shearing or nonuniform scaling An orthonormal transformation is an orthogonal transformation that preserves distances that is one that contains no scaling In the visual simulation library libpf most routines require the matrix to be orthogonal although this isn t noted in t
540. t using the currently active child or children Billboards are not intersected against since no eyepoint is defined for intersection traversals Picking pfChanPick provides a simpler interface to intersection testing by using a mouse to select geometry It uses pfNodelIsectSegs and reserves the high bit PFIS_PICK_MASK of the intersection mask in the scene graph for its own use Setting up picking with pfNodePickSetup sets this bit in the intersection mask throughout the specified subgraph but doesn t enable caching inside pfGeoSets see the Performance section of this chapter pfChanPick has an extra feature It can either return the closest intersection PFPK_M_NEAREST or return all pfHits along the picking ray PFPK_M_ALL Performance The intersection traversal uses the hierarchical bounding volumes in the scene graph to allow culling of the database and then processes candidate GeoSets by testing against their internal geometry For this reason the hierarchy should reflect the spatial organization of the database High performance culling has similar requirements see Chapter 13 Performance Trade offs IRIS Performer currently retains no information about spatial organization of data within GeoSets so each triangle in the GeoSet must be tested Although large GeoSets are good for rendering performance in the absence 185 Chapter 6 Database Traversal 186 of culling spatially localized GeoSets are
541. tState mechanism which substantially replaces the use of pfLightPoint nodes in advanced visual simulation applications The ibpr High Performance Rendering Library libpr is a low level graphics library that supports a variety of functions useful for any high performance graphics application High Performance Geometry Rendering pfGeoSet Many graphics applications are limited by CPU overhead in sending graphics commands to the Geometry Pipeline A pfGeoSet is a collection of like primitives such as points lines triangles and triangle strips pfGeoSets use tuned rendering loops to eliminate the CPU bottleneck Efficient Graphics State Management pfState IRIS Performer provides functions to control aspects of graphics library state such as lighting texture and transparency These functions operate in both immediate and libpr display list mode for direct mode changes as well as for mode caching IRIS Performer manages state changes to optimize graphics library performance Overview of the IRIS Performer Libraries Other state functions such as push pop and override allow extensive control of graphics state Graphics State Encapsulation pfGeoState A pfGeoState is an encapsulation of graphics state a graphics context Applying a pfGeoState ensures that the graphics pipeline is configured appropriately regardless of previous graphics state pfGeoStates are very efficient simplifying and accelerating graphics state managem
542. tate that yields little contribution to the scene such as being far from the eyepoint This allows you to have many more objects in your scene than if you always were drawing all objects at full complexity However you do not want the cull to be testing all LODs of an object every frame when only one will be used Again proper use of hierarchy can help pfLODs non fading can be inserted into the hierarchy with actual object pfLODs grouped beneath them If the parent LOD is out of range for the current viewpoint the child LODs will never be tested The pfLODs of each object can be placed together under a pfGroup so that no LOD tests for the object will be done if the object is outside of the viewing frustum Calling pfFlatten pfdFreezeTransforms or pfdCleanTree to remove extraneous nodes can often help culling performance Use pfFlatten to de instance and apply pfSCS node transformations to leaf geometry resulting in less work during the cull traversal This will allow both better database sorting for the draw and also better caching of matrix and bounding information which can speed up culling When these scene graph modifications are not acceptable you may reduce cull time by turning off culling of pfGeoSets but this will directly impact rendering performance by forcing the rendering of geometry that is outside the viewing frustum Tip Making the scene into a graphics library object in the draw callback can show the result of t
543. tatic Data Member class Rotor public pfDCS static int instanceCount Rotor instanceCount NULL void Rotor init instanceCount new sizeof int pfMemory instanceCount 0 Rotor Rotor instanceCount increment the creation counter A static data member whose value is set before pfConfig and never changes thereafter does not need to be allocated from shared memory The classType member of Rotor is an example of this since the class should be initialized i e Rotor init called before pfConfig libpf Objects and Multiprocessing The multiprocessing behavior of libpf objects i e those deriving from pfNode or pfUpdatable differs from that of libpr objects Both are typically created in shared memory but with a libpr object all processes share the same data members while libpf objects have a built in multiprocessing data mechanism that provides different copies in the APP CULL and ISECT stages of the IRIS Performer pipeline The term multibuffering refers to the maintenance and frame accurate updating of these data 495 Chapter 14 Programming with C mE Advanced Performance Hints 496 With a user defined subclass of a libpf class the original data elements of the libpf parent class are still multibuffered However the parallel multibuffer copies maintained in the other processes are instances of the parent class rather than the subclass This is not
544. tbind int numVerts short primtype Developing Custom Importers float pixelsize Non indexed attributes do not set if poly is indexed pfVec3 coords pfVec3 norms pfVec4 colors pfVec2 texCoords Indexed attributes do not set if poly is non indexed pfVec3 coordList pfVec3 normList pfVec4 colorList pfVec2 texCoordList Index lists do not set if poly is non indexed ushort icoords ushort inorms ushort icolors ushort itexCoords struct _pfdGeom next pfdGeom See the pfdGeoBuilder 3pf reference pages for more information on using this structure along with its sister structure the pfdPrim The above should provide a well defined framework for creating a database converter that can be used with any IRIS Performer applications via the pfdLoadFile functionality 267 Chapter 9 Importing Databases 268 However it is also important to note that there are a multitude of pfdBuilder modes and attributes that can be used to affect some of the basic methods that the builder actually uses Table 9 5 pfdBuilder Modes and Attributes Function Name Token Description pfd Get BldrMode pfd Get BldrAttr PFDBLDR_MESH_ENABLE PFDBLDR_MESH_SHOW_TSTRIPS PFDBLDR_MESH_INDEXED PFDBLDR_MESH_MAX_TRIS PFDBLDR_MESH_RETESSELLATE PFDBLDR_MESH_LOCAL_LIGHTING PFDBLDR_AUTO_COLORS PFDBLDR_AUTO_NORMALS PFDBLDR_AUTO_ORIENT PFDBLDR_AUTO_ENABL
545. ter the picture because there are several important latencies The most general measure is the total latency which measures the time between user input such as a pilot moving a control and the display of a new image computed using that input For example if the pilot of a flight simulator initiates a sudden roll after smooth level flight how long does it take for a tilted horizon to appear The total time required is the sum of latencies of components within the processing path of the simulation system The basic component latencies include the time required for each of these tasks e Input device measurement and reporting e Vehicle dynamics computation e Image generation computation e Video display system scan out The latency that matters to the user of the system is the total time delay This overall latency controls the sense of realness the system can provide Another measure combines the latencies due to image generation and video display into the visual latency Questions of latency in visual simulation applications usually refer to either total latency or visual latency The application developer selects the scope of the application and then the latency is decided by the choice of image generation mode frame rate and video output format 21 Chapter 2 IRIS Performer Basics 22 In many situations the perceived latency can be much less than the actual latency This is because the human perception of latency can be red
546. tes as possible with other pfGeoStates being built and possibly with the default pfGeoState that can be attached to a channel with pfChanGState Having created all of these primitives pfGeoSets and pfGeoStates the builder will place them in a leaf node pfGeode and optionally create a spatial hierarchy for increased culling efficiency by running the new database through a spatial breakup utility function which is also contained in libpfdu Note that the builder also allows the user to extend the notion of a graphics state by registering callback functionality through builder API and Overview of the IRIS Performer Libraries then treating this state or functionality like any other IRIS Performer state or mode although such uses of the builder are slightly more complicated In short libpfdu is a collection of utilities that effectively act as a data funnel where users enter flattened 3D graphics information and are given in return fully functional and optimized IRIS Performer run time structures Current libpfdu modules e breakup c e builder c e callbacks c e extensors c e geobuilder c e loadfile c e openfile c e rebuild c e share c e spatial c e tmesher c The ibpfdb Loader Library libpfdb is a collection of independent loaders each of which loads a particular file format into IRIS Performer Among the formats supported are OpenFlight Designer s Workbench Medit and Wavefront Each of the libpfdb l
547. th complexity of the image which is the average number of times each pixel was touched per frame The depth complexity of a scene is also be displayed in the main channel Each pixel will be colored according to how many times that pixel was written to during display rather than according to the current rendering modes The colors used range from dark blue not written to at all to bright pink written over many times This color scheme is used in calculating fill statistics the coloring is done whenever you gather fill statistics even when you aren t displaying the totals in your channel statistics display Stencil planes are used to store the number of times a pixel is written and thus to calculate fill statistics If n stencil planes are available no more than 2 writes to any given pixel will be counted By default the calculation of fill statistics uses three stencil planes to change that default call pfStatsHwAttr Fill statistics are part of the libpr pfStats statistics but can be enabled on both pfStats and pfFrameStats classes To enable fill statistics you simply do pfStatsClass statsptr PFSTATSHW_ENGFXPIPE_FILL PFSTATS_ON To enable fill statistics for a channel s pfFrameStats do pfFStatsClass pfGetChanFStats chan PFSTATSHW_ENGFXPIPE_ FILL PFSTATS_ON Examples of fill statistics can be found in perfly and in usr share Performer src pguide libpr C fillstats c Collecting and Accessin
548. the heap Alternately an application can create its own shared memory arena see the acreate 3P reference page for information on how to create an arena To allocate memory from the heap pass NULL to pfMalloc instead of an arena pointer Under normal conditions pfMalloc never returns NULL If the allocation fails pfMalloc generates a pfNotify of level PFNFY_FATAL so unless the application has set a pfNotifyHandler the application will exit Memory allocated with pfMalloc must be freed with pfFree not with the standard C library s free function Using free with data allocated by pfMalloc will have devastating results Memory allocated with pfMalloc has a reference count see pfDelete and Reference Counting in Chapter 2 for information on reference counting Managing Nongraphic System Tasks For example if you use pfMalloc to create attribute and index arrays which you then attach to pfGeoSets using pfGSetAttr IRIS Performer automatically tracks the reference counts for the arrays letting you delete the arrays much more easily than if you create them without pfMalloc All the reference counting routines including pfDelete work with data allocated using pfMalloc Note however that pfFree doesn t check the reference count before freeing memory use pfFree only when you re sure the data you re freeing isn t referenced pfGetSize returns the size in bytes of any data allocated b
549. the larger of the culling and drawing times In this case an application can spend approximately the same amount of time on each task However if both culling and drawing are performed in the same process the goal is to optimize the sum of these two times and both processes must be streamlined to minimize the total frame time Important parameters in this optimization include the number of pfGeoSets the average branching factor of the database hierarchy and the enabled channel culling traversal modes The pfDrawChanStats function see Chapter 12 Statistics can easily provide diagnostic information to aid in this tuning The average number of immediate children per node can directly affect the culling process If most nodes have a high number of children the bounding spheres are more likely to intersect the viewing frustum and all those nodes will have to be tested for visibility At the other extreme a very low number of children per node will mean that each bounding sphere test can only eliminate a small part of the database and so many nodes may still have to be traversed A good place to start is with a quad tree type organization where each node has about four children and the bounding geometry of sibling nodes are adjacent but have minimal intersection In the ideal case projected to a two dimensional plane on the ground the spatial extent of each node and its parents would form a hierarchy of boxes The transition from pfGeode
550. the matrix stack pfBeginSprite pushes the stack and pfEndSprite pops the matrix stack so the sprite transformation is limited in scope pfSprites are dependent on the viewing location and orientation and the current modeling transformation You can specify these with calls to pfViewMat and pfModelMat respectively Note that libpf based applications need not call these routines since libpf does it automatically Graphics State Display Lists libpr supports display lists which can capture and later execute libpr graphics commands pfNewDList creates and returns a handle to a new pfDispList A pfDispList can be selected as the current display list with pfOpenDList which puts the system in display list mode Any subsequent libpr graphics commands such as pfTransparency pfApplyTex or pfDrawGSet are added to the current display list Commands are added until pfCloseDList returns the system to immediate mode It is not legal to have multiple pfDispLists open at a given time but a pfDispList may be reopened in which case commands are appended to the end of the list Once a display list is constructed it can be executed by calling pfDrawDList which traverses the list and sends commands down the Geometry Pipeline pfDispLists are designed for multiprocessing where one process builds a display list of the visible scene and another process draws it The function pfResetDList facilitates this by making pfDispLists reus
551. the next LOD model For example at the near center and far points of the transition blend zone between LOD 1 and LOD 2 samples from both LOD 1 and LOD 2 are composited until the end of the transition zone is reached where all the samples are obtained from LOD 2 207 Chapter 7 Frame and Load Control 208 Table 7 2 lists the transparency factors used for transitioning from one LOD range to another LOD range Table 7 2 LOD Transition Zones Distance LOD 1 LOD 2 Near edge of blend zone 100 opaque 0 opaque Center of blend zone 50 opaque 50 opaque Far edge of blend zone 0 opaque 100 opaque LOD transitions are made smoother and much less noticeable by applying a blending technique rather than making a sudden transition Blending allows LOD transitions to look good at ranges closer to the eye than LOD popping allows Decreasing switch ranges in this way improves the ability of LOD processing to maximize the visual impact of each polygon in the scene without creating distracting visual artifacts The benefits of smooth LOD transition have an associated cost The expense lies in the fact that when an object is within a blend zone two versions of that object are drawn This causes blended LOD transitions to increase the scene polygon complexity during the time of transition For this reason the blend zone is best kept to the shortest distance that avoids distracting LOD popping artifacts Currently fade level of detail
552. the spatial arrangement of geometry beneath the pfPartition and determines an appropriate origin and spacing for the grid Because the search is exhaustive this examination can be time consuming the first time through Once a good partitioning is determined the search space can be restricted for future database loads using the partition attributes The second phase is invoked by pfUpdatePart which distributes the pfGeoSets under the pfPartition into cells in the spatial partition created by pfBuildPart pfUpdatePart needs to be called if any geometry under the pfPartition node changes During intersection traversal the segments in a pfSegSet see Intersection Requests pfSegSets in Chapter 6 are scan converted onto the grid yielding faster access to those pfGeoSets that potentially intersect the segment A pfPartition can be made to function as anormal pfGroup during intersection traversal by OR ing PFTRAV_IS_NO_PART into the intersection traversal mode in the pfSegSet Node Types Table 5 12 describes the functions for working with pfPartitions Table 5 12 pfPartition Functions Function Description pfNewPart Create a pfPartition pfPartVal Set the desired pfPartition value pfGetPartVal Find out the attributes of specified value pfPartAttr Set the desired pfPartition attribute pfGetPartAttr Find out the attributes of specified attribute pfBuildPart Construct a spatial partitioning based on the attributes
553. ther than horizontal text layouts Note that for vertically oriented fonts the origin should be such that motion by the spacing value crosses the character in other words the origin should be on the left for left to right fonts and at the top for top to bottom fonts on the bottom for bottom to top fonts and on the right for right to left fonts spatial organization The grouping together of geometric objects that are spatially close to each other in the scene graph For optimal culling performance the scene should be organized spatially sprite A transformation that rotates a piece of geometry usually textured so that it always faces the eye point stage This is a section of the IRIS Performer software rendering pipeline and is one of application culling or drawing Sometimes used to refer to either of the two non pipeline tasks of intersection and asynchronous database processing 527 Glossary 528 state State refers to attributes used to render an object that are managed during traversal State commonly falls into two areas traversal state that affects which portions of the scene graph are traversed and graphics state that affects how something is rendered Graphics state includes the current transformation the graphics modes managed by pfGeoStates and other state such as stenciling stencil decaling Animplementation method for pfLayer nodes that uses an extra bit per pixel in the frame buffer to record the Z
554. this mapping to create the interpolated image This process can be extended directly into the three dimensional domain of real time computer image generation systems and used for character animation in entertainment applications Total Animation The techniques of generalized morphing and skeleton animation can be used in conjunction to create advanced entertainment applications with life like animated characters One application of the two methods is to first perform a generalized betweening operation that builds a character with the desired pre planned animation aspects such as eye or mouth motion and then to set the matrices or other transformation operators of the skeleton transformation operation to represent hierarchical motions such as those of arms or legs The result of these animation operations is a freshly posed character ready for display Database Construction Several companies produce database modeling tools that are well integrated with IRIS Performer A selection of these products are included and described in the Friends of Performer distribution The Friends of Performer gift software is located in the usr share Performer friends directory These tools have been built to address many aspects of the database construction process Popular systems include tools that allow interactive design of geometry easy editing and placement of texture images flexible file based instancing and many other operations Special purpose tools
555. tiGen OpenFlight Format 280 McDonnell Douglas GDS Format 282 Silicon Graphics GFO Format 282 Silicon Graphics IM Format 284 AAI Graphicon IRTP Format 285 Silicon Graphics Open Inventor Format 285 Lightscape Technologies LSA and LSB Formats 287 Medit Productions MEDIT Format 291 NFF Neutral File Format 292 Wavefront Technology OBJ Format 293 Silicon Graphics PHD Format 295 Silicon Graphics PTU Format 298 SIMNET S1000 Format 300 USNA Standard Graphics Format 302 Contents 10 Silicon Graphics SGO Format 303 USNA Simple Polygon File Format 307 Sierpinski Sponge Loader 308 Star Chart Format 308 3D Lithography STL Format 309 SuperViewer SV Format 311 Geometry Center Triangle Format 314 UNC Walkthrough Format 314 libpr Basics 317 Overview 317 Design Motivation 317 Key Features 318 Geometry 319 Geometry Sets 320 3D Text 328 Graphics State 333 Rendering Modes 335 Rendering Values 340 Enable Disable 340 Rendering Attributes 341 Graphics Library Matrix Routines 352 Sprite Transformations 353 Display Lists 355 State Management 355 State Override 357 pfGeoState 357 Windows 363 Configuring the framebuffer of a pfWindow 367 pfWindows and GL Windows 370 Manipulating a pfWindow 372 Communicating with the Window System 374 More pfWindow Examples 374 libpr Sample Code 378 11 12 Managing Nongraphic System Tasks 384 Clocks 384 Memory Allocation 385 Asynchronous I O 391 Error Handling and Notification 391 File Searc
556. time there is no way of querying the result of a pfAsyncDelete request so care should be taken that the object to be deleted has no reference counts or memory leaks will result Rules for Invoking Functions While Multiprocessing There are some restrictions on which functions can be called from an IRIS Performer process while multiple processes are running Some specialized processes such as the process handling the draw stage can call only a few specific IRIS Performer functions and can t call any other kinds of functions This section lists general and specific rules concerning function invocation in the various IRIS Performer and user processes In this section the term the draw process refers to whichever process is handling the draw stage regardless of whether that process is also handling other stages Similarly the cull process and the application process refer to the processes handling the cull and application stages respectively Successful Multiprocessing With IRIS Performer This is a general list of the kinds of routines you can call from each process application configuration routines creation and deletion routines set and get routines and trigger routines such as pfAppFrame pfSync pfFrame database creation and deletion routines set and get routines cull pfDBase pf MergeBuffer pfCull Q pfCullPath IRIS Performer graphics routines draw pfClearChan pfDraw pfDrawC
557. tion Y Nodes pfAddChild current_vehicle_type tank_position pfAddChild current_vehicle_type heli_position pfAddChild car_position car pfAddChild tank_position tank pfAddChild heli_position heli The following shows how one might use IRIS Performer to manipulate the scene graph at run time by adding and removing children from branch nodes in the scene graph xj for j 0 3 lt 4 Jjtt for i 0 i lt 4 i pfGroup this_terrain this_terrain pfGetChild scene j 4 i if pfGetNumChildren this_terrain gt 2 this_tank pfGetChild this_terrain 2 if is_tank_disable this_tank pfRemoveChild this_terrain this_tank pfAddChild disabled_tanks this_tank 119 Chapter 5 Nodes and Node Types Working With Nodes 120 This section describes the basic concepts involved in working with nodes It explains how shared instancing can be used to create multiple copies of an object and how changes made to a parent node propagate down to its children A sample program that illustrates these concepts is presented at the end of the chapter Instancing A scene graph is typically constructed at application initialization time by creating and adding new nodes to the graph If a node is added to two or more parents it is termed instanced and is shared by all its parents Instancing is a powerful mechanism that saves memory and makes modeling easier libpf sup
558. tion 518 statistics 432 See also statistics values 333 340 graphics context definition 518 graphics libraries database sorting 458 input handling 459 460 IRIS GL xxv linking 40 objects 464 OpenGL xxv overview 40 41 See also IRIS GL OpenGL graphics state 32 ground 32 grout digital 209 GUI 3 H Haeberli Paul 303 Haines Eric 292 half spaces 409 Halvorson Mike 286 Hamilton Sir William Rowan 404 handling flimmering 131 Har El Zvi 295 header files 61 483 heading 95 defined 518 headlights 134 heap 509 defined 518 Hein Piet 276 Helman James xxix help 93 131 64 bit compilation 69 accessing the FTP site xxxv accessing the mailing list xxxv accessing the web page xxxv C argument passing 488 channel groups 105 channels 92 clearing a channel 177 compiling and linking 67 constant frame rates 22 database formats 269 database paging 220 default shared arena size 387 display lists 322 drawing a background 231 drawing text 138 finding files 65 flimmering 516 frame rates 191 Friends of Performer 28 geometry specification 319 getting started 3 graphics attributes 333 inheriting transformations 146 initializing IRIS Performer 62 instancing 120 interfacing C and C code 489 IRIX 6 2 issues 70 level of detail 198 life like character animation 26 lighting 133 main simulation loop 65 morphing 244 multiple pipelines 74
559. tisampling stores a complete set of pixel information for each of the several subpixels This includes such information as color transparency and most importantly a Z buffer value Providing multiple independent Z buffered subpixels the so called sub pixel Z buffer per image pixel allows opaque polygons to be drawn in an arbitrary order since the subpixel Z comparison will implement proper visibility testing Converting the multiple color values that exist within a pixel into a single result can either be done as each fragment is rendered into the multisampling buffer or after all polygons have been rendered For best visual result transparent polygons are rendered after all opaque polygons have been drawn Survey of Visual Simulation Techniques Texture Mapping The most powerful incremental feature of image generation systems beyond the initial capability to draw geometry is texture mapping the ability to apply textures to surfaces These textures consist of synthetic or photographic images that are displayed in place of the surfaces of geometric primitives to modify their surface appearance reflectance or shading properties For each point on a texture mapped surface a corresponding pixel from the texture map is chosen to display instead giving the appearance of warping the texture into the shape of the object s surface Surface Appearance The most obvious use of texture mapping is to generate the appearance of surface det
560. to GLdebug history or progname pid trace for ogldebug 8 Quit and examine the output Note Since IRIS Performer avoids unnecessary mode settings recording one frame shows modes that are set during that frame but it doesn t reflect modes that were set previously It s therefore best to have a program that can come up in the desired location and with the desired modes then grab the first two frames one for initialization and one for continued drawing Using g iprof to Find Performance Bottlenecks You can use the IRIS GL graphics profiling utility glprof to estimate where there are graphics bottlenecks so that you can tune the database You don t have to relink the program or run it in single process mode to use glprof Use glprof to e See if certain views or individual objects are inherently fill or transform limited Ifa scene or object is fill limited there can be more complex geometry in the LOD s Ifa scene or object is transform limited you need to simplify or add LOD s especially for small objects e See significant mode changes e Get additional scene graphics state and fill statistics such as the number of pixels fixed with polygons of different sizes and different modes Note that since only glprof simulates the graphics pipeline it may not always be entirely accurate in predicting performance 469 Chapter 13 Performance Tuning and Debugging You can use predraw callbacks on nodes to output
561. tories 251 libpfdu database converter functions 252 Loader Name Composition 254 libpfdu database converter management functions 255 pfdBuilder Modes and Attributes 268 Supported Database Formats 269 Geometric Definitions in LSA Files 288 Object Tokens in the SGO Format 305 Mesh Control Tokens in the SGO Format 306 pfGeoSet Routines 320 Geometry Primitives 321 Attribute Bindings 327 pfFont Routines 329 pfString Routines 332 pfGeoState Mode Tokens 335 pflransparency Tokens 336 pfGeoState Value Tokens 340 Enable and Disable Tokens 340 Rendering Attribute Tokens 341 Texture Image Sources 344 Texture Load Modes 346 Texture generation modes 348 pfFog Tokens 350 pfHlightMode Tokens 351 Matrix Manipulation Routines 353 pfSprite rotation modes 354 pfGeoState Routines 361 pfWinType Tokens 365 pfWinFBConfigAttrs Tokens 368 Window System Types 371 Table 10 22 Table 10 23 Table 10 24 Table 10 25 Table 10 26 Table 10 27 Table 11 1 Table 11 2 Table 11 3 Table 11 4 Table 11 5 Table 11 6 Table 11 7 Table 11 8 Table 11 9 Table 11 10 Table 11 11 Table 11 12 Table 14 1 Table 14 2 Table 14 3 Table 14 4 Table 14 5 Table 14 6 pfWinMode Tokens 373 pfVClock Routines 385 Memory Allocation Routines 386 pfNotify Functions 392 Error Notification Levels 392 pfFilePath Routines 393 Routines for 3 Vectors 398 Routines for 4x4 Matrices 399 Routines for Quaternions 405 Matrix Stack Routines 407 Routines to
562. tors in series to a single pipeline s video output Because each monitor receives the same display image a masking bezel is used to obscure all but the relevant portion of each display surface The three multiple channel concepts described here can be used in combination For example use of three RealityEngine pipelines each equipped with the Multi Channel Option allows creation of up to 18 independent video displays The channel tiling method can also be used for some or all of these displays Example 4 8 shows how to use multiple channels on separate pipes Example 4 8 Multiple Channels One Channel per Pipe pfChannel Chan MAX_CHANS void InitChannel int NumChans Initialize each channel on a separate pipe for i 0 i lt NumChans i Chan i pfNewChan pfGetPipe i 103 Chapter 4 Setting Up the Display Environment 104 Make channel n 2 the master channel can be any channel x7 ViewState gt masterChan Chan NumChans 2 long share Get the default channel sharing mask share pfGetChanShare ViewState gt masterChan Add in the viewport share bit share PFCHAN_VIEWPORT if GangDraw add GangDraw to channel share mask share PFCHAN_SWAPBUFFERS_HW pfChanShare ViewState gt masterChan share Attach channels for i 0 i lt NumChans i if Chan i ViewState gt masterChan pfAttachChan ViewState gt masterChan Chan
563. transparent because IRIS Performer manages the difficult multiprocessing issues such as process timing synchronization and data coherence for you 29 Chapter 2 IRIS Performer Basics 30 Pipes Pipe Windows and Channels pfPipe pfPipeWindow pfChannel libpf provides software constructs to facilitate rendering a visual database A pfPipe is a rendering pipeline that renders one or more pfChannels into one or more pfPipeWindows A pfChannel is a view into a visual database equivalent to a viewport within a pfPipeWindow IRIS Performer supports multiple pfChannels on a single pfPipeWindow multiple pfPipeWindows on a single pfPipe and multiple pfPipes per machine for multichannel multiwindow and multipipe operation Frame synchronization between channels is provided for simulations that display multiple simultaneous views on different hardware displays Visual Database pfScene libpf supports a general database hierarchy defined as a directed acyclic graph of nodes IRIS Performer provides specialized node types useful for visual simulation applications Grouping Nodes e pfScene Root node of a visual database e pfGroup Branch node which may have children e pfSCS Static coordinate system e pfDCS Dynamic coordinate system e pfLayer Coplanar geometry node e pfLOD Level of detail selection node e pfSwitch Select among children e pfSequence Sequenced animation node e pfPartition Collection of geomet
564. tress on transition distances Level of Detail Management These LOD states can then be attached to either single or multiple LOD nodes such that the LOD behavior of groups or classes of objects can be different and be easily modified The reference pages for pfLODLODState and pfLODLODStateIndex contain detailed information on how to attach pfLODStates LOD states are useful because in a particular scene there often exists an object of focus such as a sign a target or some other object of particular visual significance that needs to be treated specially with regard to visual importance and thus LOD behavior It stands to reason that this particular object or small group of objects should be at the highest detail possible despite being farther away than other elements in the scene which might not be as visually significant In fact it might be feasible to diminish the detail of these less important objects like rocks and trees in favor of the other more important objects despite these objects being further relatively in range In this case one would just create two LOD states The first would be for the important objects and would effectively disable the effect of stress on these nodes as well as scale the switch ranges such that the object s would maintain more detail for further ranges The second LOD state would be used to make the objects of less importance be more responsive to system stress and possibly scale their switch ranges
565. tributes and routines of all its parent nodes in the type hierarchy Nodes Figure 5 1 shows the type hierarchy for the libpf node types piGeode pfBillboard pfText pfGroup pfLightPoint pfLightSource pfScene pfPartition pflayer pfLOD pfSCS pfSwitch pfSequence pfMorph pfDCS Figure 5 1 Nodes in the IRIS Performer Hierarchy 113 Chapter 5 Nodes and Node Types 114 Table 5 1 lists the basic node class and gives a simple description for each node type Table 5 1 IRIS Performer Node Types Node Type Node Class Description pfNode Abstract Basic node type pfGroup Branch Groups zero or more children pfScene Root Parent of the visual database pfSCs Branch Static Coordinate System pfDCS Branch Dynamic Coordinate System pfSwitch Branch Selects among multiple children pfSequence Branch Sequences through its children pfLOD Branch Level of detail node pfLayer Branch Renders coplanar geometry pfLightPoint Leaf Contains light point specifications pfLightSource Leaf Contains specifications for a light source pfGeode Leaf Contains geometric specifications pfBillboard Leaf Rotates geometry to face the eyepoint pfPartition Branch Partitions geometry for efficient intersections pfMorph Branch Morphs attribute data of its children pfText Leaf Renders 2D and 3D text
566. true if present STEREO Boolean Allocate left and right stereo color buffers true if allocates back left and back right if present DOUBLEBUFFER is specified AUX_BUFFER integer gt 0 Number of additional color buffers to allocate RED_SIZE integer gt 0 Minimum number of bits color for GREEN_ SIZE components R G and B will all be the BLUE_SIZE same and be the maximum specified ALPHA_ SIZE Alpha may be different DEPTH_SIZE integer gt 0 Number of bits in the depth buffer Windows Table 10 20 continued pfWinFBConfigAttrs Tokens PFFB_ Token Value Description STENCIL integer gt 0 Number of bits allocated for stencil One is used by pfDecal rendering and three or four are used by the hardware fill statistics in pfStats ACCUM_RED_SIZE integer gt 0 Number of bits per RGBA component for ACCUM_GREEN_SIZE the accumulation color buffer ACCUM_BLUE_SIZE ACCUM_ALPHA_ SIZE USE_GL Boolean Accepted for compatibility with X true if routines Has no effect present You may get back a framebuffer configuration that is better than the one you requested IRIS Performer will give you back the maximum framebuffer configuration that meets your request that will not add any serious performance degradations There are specific machine dependent instances where when possible for performance reasons we do limit the framebuffer configuration See the pfChooseWinFBConfig reference page for the specific details If you desi
567. ttribute Inheritance 112 pfNode 115 pfGroup 117 Working With Nodes 120 Instancing 120 Bounding Volumes 123 Node Types 125 pfScene Nodes 125 pfSCS Nodes 126 pfDCS Nodes 126 pfSwitch Nodes 127 pfSequence Nodes 128 pfLOD Nodes 130 pfLayer Nodes 131 pfLightPoint Nodes 132 pfLightSource Nodes 133 pfGeode Nodes 137 pflext Nodes 138 pfBillboard Nodes 140 pfPartition Nodes 144 Sample Program 146 vi Database Traversal 153 Scene Graph Hierarchy 155 Database Traversals 155 State Inheritance 156 Database Organization 156 Application Traversal 157 Cull Traversal 158 Traversal Order 159 Visibility Culling 159 Organizing a Database for Efficient Culling 163 Sorting the Scene 166 Paths Through the Scene Graph 168 Draw Traversal 169 Controlling and Customizing Traversals 169 pfChannel Traversal Modes 169 pfNode Draw Mask 170 pfNode Cull and Draw Callbacks 171 Process Callbacks 174 Process Callbacks and Passthrough Data 176 Intersection Traversal 179 Testing Line Segment Intersections 179 Intersection Requests pfSegSets 180 Intersection Return Data pfHit Objects 180 Intersection Masks 181 Discriminator Callbacks 183 Line Segment Clipping 184 Traversing Special Nodes 185 Picking 185 Performance 185 Intersection Methods for Segments 186 vii Contents viii Frame and Load Control 191 Frame Rate Management 191 Selecting the Frame Rate 192 Achieving the Frame Rate 192 Fixing the Frame Rate 193 Level of Detail Managem
568. tune the application process Use pixie for basic block counting and use prof for program counter PC sampling PC sampling gives run time estimation of where significant amounts of time are spent whereas basic block counting will report the number of times a given instruction is executed To isolate statistics for the application process even in single process models run the application through pixie or prof in APP_CULL_DRAW mode to separate out the process of interest Both pixie and prof can generate statistics for an individual process When using IRIS Performer DSO libraries with prof you may want to provide the dso option to prof with the full pathname of the library of interest to have IRIS Performer routines included in the analysis When using pixie you 467 Chapter 13 Performance Tuning and Debugging 468 will need to have the pixie versions of the DSO libraries in your LD_LIBRARY_PATH Additionally you will need a pixie version of the loader DSO for your database in your LD_LIBRARY_PATH You may have to pixie the loader DSO separately since pixie will not find it automatically if your executable was not linked with it When using prof to do PC sampling link with unshared libraries exclusively and use the p option to Id Then set the environment variable PROFDIR to indicate the directory in which to put profiling data files When profiling run the program for a while so that the initialization will not be signific
569. ture image including any required minification or magnification levels into texture memory pfSubloadTex and pfSubloadTexLevel can also be used in the drawing process to do an immediate load of texture memory managed by the given pfTexture and these routines allow you to specify all loading parameters source origin size etc This is useful for loading different images for the same pfTexture in different graphics pipelines A special pfTexFormat formatting mode PFTEX_SUBLOAD_FORMAT allows part or all of the image in texture memory owned by the pfTexture to be replaced via pfApplyTex pfLoadTex or pfSubloadTex without having to go through the expensive reformatting phase This allows you to quickly update the image of a pfTexture in texture memory The PFTEX_SUBLOAD_FORMAT used with an appropriate pfTexLoadSize Graphics State and pfTexLoadOrigin allows you to control what part of the texture will be loaded by subsequent calls to pfLoadTex or pfApplyTex There are also different loading modes that cause pfApplyTex to automatically reload or subload a texture from a specified source If you want the image of a pfTexture to be updated upon every call to pfApplyTex you can set the loading mode of the pfTexture with pfTexLoadMode to be PFTEX_BASE_AUTO_REPLACE pfTexLoadImage allows you to continuously update the memory location of an IMAGE source texture without triggering any reformatting of the texture Not
570. ty is to increase the size of the shadow map but this will decrease performance Projected textures and shadows both use texture mapping so if your scene is texture mapped multiple rendering passes are required to combine the projected texture with the normal scene textures In pfDraw pfChannels assume the scene is textured and automatically render the scene multiple times However if your scene is not textured you can avoid a complete rendering pass by setting the PFMPASS_NONTEX_SCENE bit in the PFTRAV_MULTIPASS mode given to pfChanTravMode Example 8 3 is a code snippet which shows how to set up both projected texture and shadowing pfLightSources Example 8 3 Projected texture and shadow pfLightSources pfFrustum shadFrust pfLightSource shad proj pfDCS shadDCS pro DCS pfTexture tex Create and configure shadow frustum shadFrust pfNewFrust arena pfMakeSimpleFrust shadFrust 60 0f pfFrustNearFar shadFrust 1 0f 100 0f Create and configure red shadow casting light source shad pfNewLSource pfLSourceMode shad PFLS_SHADOW_ENABLE 1 pfLSourceAttr shad PFLS_PROJ_FRUST shadFrust pfLSourceColor shad PFLT_DIFFUSE 1 0f 0 0f 0 0f pfLSourceVal shad PFLS_INTENSITY 5f 243 Chapter 8 Creating Visual Effects pfLSourcePos shad 0 0f 0 0f 0 0f 1 0f make local Create and configure blue spotlight proj pfNewLSource tex pfNewTex arena
571. uced by anticipating the user s inputs This means that reducing perceived latency is largely a matter of accurate prediction Consistent Frame Rates To be acceptable by human observers interactive graphics applications and immersive virtual environments in particular depend on a consistent frame rate Human perceptions are attuned to continuous update from natural scenes but seem tolerant of discrete images presented at rates above 15 frames per second as long as the frame rate is consistent When latency grows large or frame rates waver headaches and nausea often result Attaining a constant frame rate for a constant scene is easy What s hard is maintaining a constant frame rate through wildly varying scene content and complexity Designers of image generation systems use several approaches to achieve a constant programmer selected frame rate The first and most basic method is to draw all scenes in such a simple way that they can be viewed from any location without altering the chosen frame rate This conservative approach is much like always driving in low gear just in case a hill might be encountered Implementing it simply means identifying and planning for the worst case situation of graphics load Although this may be reasonable in some cases in general it s unacceptably wasteful of system resources A second approach is to discard cull database objects that are positioned completely outside the viewing frustum This re
572. ucture If you pass NULL as the arena the attribute is allocated from the heap and isn t sharable in a non shared address space fork multiprocessing application Allattributes can be applied directly referenced by a pfGeoState or captured by a display list When changing an attribute that change isn t visible until the attribute is reapplied Detailed coverage of attribute implementation is available in the reference pages Texture IRIS Performer supports texturing through pflextures and pfTexEnvs which are roughly analogous to graphics library textures see texdef2d for IRIS GL or glTexImage2D for OpenGL and texture environments see IRIS GL s tevdef 3g or OpenGL s glTexEnv A pfTexture defines a texture image format and filtering A pfTexEnv specifies how the texture should interact with the colors of the geometry it s applied to You need both to Graphics State display textured data but you don t need to specify them both at the same time For example you could have pfGeoStates each of which had a different texture specified as an attribute and still use an overall texture environment specified with pfApplyTEnv A pfTexture is created by calling pfNewTex If the desired texture image exists as a disk file in IRIS libimage format the file often has a rgb suffix you can call pfLoadTexFile to load the image into CPU memory and set the image format Otherwise pfTexImage lets you directly
573. ulate either directionality or both perspective fading and fog punch through This frees the CPU from making these expensive calculations Example 8 2 is a portion of the sample program Ipstate c found in usr share Performer src pguide libpf C Example 8 2 How to set up a pfLPointState define NPOINTS2 30 define NPOINTS NPOINTS2 NPOINTS2 2 static pfGeode initLPoints void pfLPointState 1 psy pfTexGen tgen pfTexture tex pfGeoState gst pfGeode gd pfGeoSet gs pfVec3 norms colors coords pfMatrix squash squashInvTransp float phi dphi theta dtheta int i Jj Ky void arena pfGetSharedArena Set up pfLPointState lps pfNewLPState arena Enable perspective size computation pfLPStateMode lps PFLPS_SIZE_MODE PF_ON Clamp point size between 25 and 4 pixels pfLPStateVal lps PFLPS_SIZE_MIN_PIXEL 25f pfLPStateVal lps PFLPS_SIZE_MAX PIXEL 4 0f Light Points Real world point size is 15 meters pfLPStateVal lps PFLPS_SIZE_ACTUAL 15f Fade points smaller than 2 pixels pf LPStateVal lps PFLPS_TRANSP_PIXEL_SIZE 2 0f Linear fad
574. ulations Consequently it s impossible for one plane to be flying with its landing gear retracted while another is on a runway with its landing gear down Cloned instancing provides the solution to this problem by cloning creating new copies of variable nodes in the subgraph Leaf nodes containing geometry are not cloned and are shared to save memory Cloning the airplane model generates new articulation nodes which can be modified independently of any other cloned instance The cloning operation pfClone is actually a traversal and is described in detail in Chapter 6 Figure 5 3 shows the result of cloned instancing As in the previous figure the left half of the drawing represents the situation before the operation and the right half shows the result of the operation 121 Chapter 5 Nodes and Node Types Root coordinate system Leaf Figure 5 3 Cloned Instancing The cloned instancing operation constructs new copies of each internal node of the shared hierarchy but uses the same shared instance of all the leaf nodes In use this is an important distinction because the number of internal nodes may be relatively few while the number and content of geometry containing leaf nodes is often quite extensive Nodes G1 and G2 in Figure 5 3 are the groups that form the root nodes after the cloned instancing operation is complete Node P is the parent or root node of the instanced object and D is a dynamic coordinate sy
575. une your graphics application for maximum performance on your system Now that you ve seen what IRIS Performer can do it s up to you to decide how to proceed You can read through the remainder of this programming guide beginning with the overview in Chapter 2 or you can skip directly to a chapter that describes a specific task you need to perform Chapter 2 IRIS Performer Basics This chapter provides a brief overview of IRIS Performer s features and component libraries Chapter 2 What Is IRIS Performer IRIS Performer Basics This chapter provides background for and an introduction to IRIS Performer including a survey of visual simulation techniques descriptions of features and libraries and discussion of some of the specific details of IRIS Performer structure and use IRIS Performer is an extensible software toolkit for creating real time 3D graphics Typical applications are in the fields of visual simulation entertainment virtual reality broadcast video and computer aided design IRIS Performer provides a flexible intuitive toolkit based solution for developers who want to optimize performance on Silicon Graphics systems The main components of the toolkit are four dynamic shared objects DSOs as shown in Table 2 1 support files for those libraries such as the header files and source code for sample applications Table 2 1 IRIS Performer Libraries DSO Name Header File Description
576. uration of this chapter bold lowercase letters represent vectors and bold uppercase letters represent matrices X indicates cross product denotes dot product and vertical bars indicate the magnitude of a vector Table 11 1 Routines for 3 Vectors Routine Effect Macro Equivalent pfSetVec3 d x y z d x y Z PFSET_VEC3 pfCopyVec3 d v d v PFCOPY_VEC3 pfNegateVec3 d v d v PFNEGATE_VEC3 pfAddVec3 d v1 v2 d v v PFADD_VEC3 pfSubVec3 d v1 v2 d v v PFSUB_VEC3 pfScaleVec3 d s v d sv PFSCALE_VEC3 pfAddScaledVec3 d v1 s v2 d v sv2 PFADD_SCALED_VEC3 pfCombineVec3 d s1 v1 s2 v2 pfNormalizeVec3 d pfCrossVec3 d v1 v2 pfXformPt3 d v m pfFullXformPt3 d v m pfXformVec3 d v m pfDotVec3 v1 v2 pfLengthVec3 v pfSqrDistancePt3 v1 v2 pfDistancePt3 v1 v2 d s1Vq S2V2 d d ldl d v Xv d vM where v Vy Vy v and M is the 4x3 submatrix d vM d where V Vy Vy Vz 1 d vM where v Vy Vy Vz 0 v1 v2 Ivl lv v41 Ivo v4 PFCOMBINE_VEC3 none none none none none PFDOT_VEC3 PFLENGTH_VEC3 PFSOR_DISTANCE_PT3 PFDISTANCE_PT3 Matrix Operations Matrix Operations Table 11 1 continued Routines for 3 Vectors Routine Effect Macro Equivalent pfEqualVec3 v1 v2 returns TRUE if PFEQUAL_VEC3 v1 V2 FALSE otherwise pfAlmostEqualVec3 v1 v2 tol returns TRUE if each element of v is within tol of the correspo
577. ure of IRIS Performer s scene definition databases and component data types Chapter 5 Nodes and Node Types An application based on IRIS Performer usually reads in a visual database from a file then builds an internal data structure incorporating the information in that database This data structure is called a scene graph each element in the data structure is called a node This chapter describes the types of nodes IRIS Performer uses to represent scenes internally IRIS Performer provides many functions for creating querying modifying and traversing scene graphs such functions are also described here Note that this chapter focuses on the data types themselves rather than instances of those types Chapter 6 Database Traversal includes discussion of traversing sample scene graphs in terms of actual objects rather than abstract data types Objects in a scene graph which is to say instances of node types have a hierarchical relationship based on the way the scene is laid out The node types themselves on the other hand have an entirely different kind of hierarchical relationship based on the ways in which each node type is like other node types For instance the pfBillboard node type is a subclass of the general pfNode node type This concept is discussed in more detail in the section of this chapter titled Attribute Inheritance on page 112 111 Chapter 5 Nodes and Node Types Nodes 112 A sc
578. valid for access in the draw process Yes before opened X Yes IRIS GL ID must be valid in the draw process Yes but the context must be created in the draw process No No Yes Yes Yes Yes Yes Yes Yes Yes Yes before opened Yes Yes Yes Using pfPipeWindows Example 4 3 showed a case where custom IRIS GL code was used in the pfPWinConfigFunc callback to configure the framebuffer for a window However IRIS Performer provides GL independent framebuffer configuration utilities In most cases pfPWinFBConfigAttrs pwin attrs can be used to select a framebuffer configuration for your pfPipeWindow based on the array of attribute tokens attrs If attrs is NULL the default framebuffer configuration will be selected If attrs is not NULL the rules for default values follow the rules for configuring windows in OpenGL and X which are different from values in the IRIS Performer default window configuration Window framebuffer configuration for pfPipeWindows is identical to that of pfWindows and is discussed in more detail in Chapter 10 libpr Basics but the following is a simple example of the specification of framebuffer configuration taken from the sample source code example program usr share Performer src pguide libpf C pipewin c Example 4 5 Configuration of a pfPipeWindow Framebuffer static int FBAttrs PFFB_RGBA PFFB_DOUBLEBUFFER PFFB_DEPTH_SIZE 24
579. ve Performer work during culling by having to unwrap fewer pfGeoStates and thus possibly increase frame rate There are several database utility functions in libpfdu designed to help with this optimization pfdMakeSceneGState returns an optimal pfGeoState based on a list of pfGeoStates pfdOptimizeGStateList takes an existing global pfGeoState anew global pfGeoState and a list of pfGeoState s that should be optimized and cause all attributes of pfGeoStates in the list of pfGeoStates to be inherited if they are the same as the attribute in the new global pfGeoState Lastly pfdMakeSharedScene will cause this optimization to happen for all of the pfGeoStates under the pfScene that was passed into the function For 125 Chapter 5 Nodes and Node Types 126 more information on pfGeoStates see Chapter 10 libpr Basics which discusses libpr in more detail For more information of the creation and optimization of databases see Chapter 9 Importing Databases which discusses building database converters and libpfdu pfSCS Nodes A pfSCS is a branch node that represents a static coordinate system A pfSCS node contains a fixed modeling transformation matrix that cannot be changed once it is created pfSCS nodes are useful for positioning models within a database For example a house that is modeled at the origin should be placed in the world with a pfSCS because houses rarely move during program execution Use
580. vides the capability to convert from UTM to assembly coordinates The assembly coordinate frame is a topocentric rectangular grid located at the southwest corner of the assembly area Loader details The loader creates a scene graph spatially organized as a quadtree Each leaf node contains LAND and MICROTERRAIN polygons NETWORK elements and other data pfdLoadFile uses the function pfdLoadFile_s1k to load S1000 format files into IRIS Performer run time data structures USNA Standard Graphics Format The sgf format is used at the United States Naval Academy as a standard graphics format for geometric data The loader was developed based on the description of the standard graphics format as described by David F Rogers and J Alan Adams in the book Mathematical Elements for Computer Graphics The IRIS Performer sgf format loader is located in the directory usr share Performer srcflibflibpfdb libpfsef Here is the vector definition for four stacked squares in SGF form 0 0 0 Iy 00 eg LO 0 1 O 0 0 0 1 0e37 1 0637 T0637 Description of Supported Formats Oy Oye L ago d ey Lig Ojo hy L Oz 0 1 1 06st Ls 0637 y T0S37 Oz O 2 Poy 2 Iy ay Op Ip 2 0 0 2 1 0e37 1 0637 14 0637 0 0 3 Li 0y 3 the le 3 0 45 3 0 0 3 1 0637 1 0637 1 0637 pfdLoadFile uses the function pfdLoadFile_sgf to load SGF format files into IRIS Performer run time data structures Silicon Graphics SGO Forma
581. w These routines are not interchangeable pfWindow routines cannot accept pfPipeWindows and visa versa Some details of pfWindow and thus pfPipeWindow functionality are discussed with pfWindows Windows have some intrinsic type attributes that must be set before the window is opened The selection of the screen of a window is determined by the pfPipe that it is opened on or set for both the pfWindow and its pfPipe with the call pfPWinScreen or else when the window is finally opened The window system configuration of the window must also be set before the window is opened Windows under OpenGL operation will always be X windows However under IRIS GL operation a pfPipeWindow will by default be a pure IRIS GL window To render IRIS GL into an X window the X window type must be specified with the command pfPWinType pwin PFPWIN_TYPE_X An open window must be closed for its type to be changed The window type argument is actually a bitmask and the type of a pfPipeWindow can include the attributes listed in Table 4 1 Table 4 1 pfPWinType Tokens Token Type Attributes PFPWIN_TYPE_X Rendering will be done to an X window Ignored by OpenGL as all OpenGL rendering is done to X windows PFPWIN_TYPE_STATS The window s normal drawing configuration will support graphics statistics This affects framebuffer configuration and fill statistics PFPWIN_TYPE_SHARE The pfPipeWindow will automatically be attached to the first pfPipeWindow
582. window Under multipipe operation the screen of all pfPipes must be determined before the pipes are configured by pfConfigStage or the first call to pfFrame Once the screen of a pfPipe has been set it cannot be changed All windows of a pfPipe must be opened on the same screen A graphics window is associated with a pfPipe through the pfPipeWindow mechanism which is the subject of the next section Using pfPipeWindows If you do not create a pfPipeWindow IRIS Performer will automatically create and open a full screen window with a default configuration for your pfPipe Once you create and initialize a pfPipe you can query information about its configuration parameters pfGetPipeScreen returns the index number of the hardware pipeline for the pfPipe starting from zero On single pipe Using Pipes systems the return value will be zero If no screen has been set the return value will be 1 pfGetPipeSize returns the full screen size in pixels of the rendering area associated with a pfPipe Example of pfPipe Use The sample source code shipped with IRIS Performer includes several simple examples of pfPipe use in both C and C Specifically look at the following examples under the C and C directories in usr share Performer src pguide libpf such as hello c simple c and multipipe c Example 4 1 illustrates the basics of using pipes The code in this example is adapted from IRIS Performer sample programs Exampl
583. x pfPopMStack 407 pfPopState 356 pfPositionSprite 354 pfPostMultMat 401 pfPostMultMStack 407 pfPostRotMat 401 pfPostRotMStack 407 pfPostScaleMat 401 pfPostScaleMStack 407 pfPostTransMat 401 pfPostTransMStack 407 pfPreMultMat 401 pfPreMultMStack 407 pfPreRotMat 401 pfPreRotMStack 407 pfPreScaleMat 401 pfPreTransMat 401 pfPrint 45 321 328 440 pfPushIdentMatrix 353 pfPushMatrix 172 353 pfPushMStack 407 pfPushState 224 356 pfPWinConfigFunc 85 87 88 89 pfPWinFBConfig 83 88 pfPWinFBConfigAttrs 83 88 89 pfPWinFullScreen 79 80 88 pfPWinGLCxt 88 pfPWinIndex 83 88 pfPWinMode 83 88 pfPWinOriginSize 79 87 88 pfPWinScreen 81 88 pfPWinShare 88 pfPWinType 81 88 pfPWinWSDrawable 88 90 pfPWinWSWindow 88 90 pfQuatMeanTangent 405 pfQueryFeature 349 449 pfQueryFStats 438 442 pfQueryGSet 321 pfQueryHit 180 181 417 418 pfQueryStats 438 442 554 pfQuerySys 370 pfQueryWin Q 370 371 pfReadFile 391 pfRef 47 pfReleaseDPool 389 pfRemoveChan 105 pfRemoveChild 117 221 pfRemoveGSet 138 139 pfReplaceGSet 46 138 139 pfResetDList 355 pfResetMStack 407 pfResetStats 437 pfRotate 353 pfScale 353 pfScaleVec3 398 pfSceneGState 125 450 pfSeekFile 391 pfSegIsectPlane 416 pfSeglIsectTri 416 pfSelectBuffer 220 511 pfSelectState 35
584. x y and z all specified by c returns in q a quaternion with the rotation specified by s returns in d the rotation and translation specified bys Set rth row of D equal to x y z w x y z w rth row of M Set cth column of D equal to x y z w x y z w cth column of M Set rth row of D equal to v d rth row of M Set cth column of D equal to v d cth column of M PFMAKE_TRANS_MAT PFMAKE_SCALE_MAT none none none PFSET_MAT_ROW PFGET_MAT_ROW PFSET_MAT_COL PFGET_MAT_COL PFSET_MAT_ROWVEC3 PFGET_MAT_ROWVEC3 PFSET_MAT_COLVEC3 PFGET_MAT_COLVEC3 Matrix Operations Table 11 2 continued Routines for 4x4 Matrices Routine Effect Macro Equivalent pfCopyMat d m D M PFCOPY_MAT pfAddMat d m1 m2 D M M none pfSubMat d m1 m2 D M M gt none pfMultMat d m1 m2 D M M none pfPostMultMat d m D DM none pfPreMultMat d m D MD none pfTransposeMat d m D MT none pfPreTransMat d m x y Z D TM where T none translates by x y z pfPostTransMat d x y z m D MT where T none translates by x y z pfPreRotMat d deg x y z m D RM whereR none rotates by deg around x y z pfPostRotMat d m deg x y z D MR whereR none rotates by deg around x y z pfPreScaleMat d x y z m D SM where S none scales by x y z pfPostScaleMat d m x y z D MS where S none scales by x y z pfInvertFullMa
585. xtures to be freed before applying the new texture This method has no restrictions on the texture list but is less efficient than the previous method Finally texture list textures can be treated as completely independent textures that should all be kept resident in memory for rapid access upon their application pfTexFilter sets a desired filter on a pfTexture The minification and magnification texture filters are described with bitmask tokens If filters are partially specified IRIS Performer will fill in the rest with machine dependent fast defaults The PFTEX_FAST token can be included in the bitmask to allow IRIS Performer to make machine dependent substitutions where there are large performance differences There are a variety of texture filter functions that can improve the look of textures when they are minified and magnified By default textures use MIPmapping when minified though this costs an extra 1 3 in storage space to store the minification levels Each level of minification or magnification of a texture is twice the size of the previous level Minification levels are Graphics State indicated with positive numbers and magnification levels are indicated with non positive numbers The default magnification filter for textures is bilinear interpolation The use of detail textures and sharpening filters can improve the look of magnified textures Detailing actually uses an extra detail texture that you provide that is based
586. y Attribute Bindings Attribute bindings specify where in the definition of a primitive an attribute has effect You can leave a given attribute unspecified otherwise its binding location is one of the following e overall one value for the entire pfGeoSet e per primitive e per vertex Only certain binding types are supported for some attribute types Table 10 3 shows the attribute bindings that are legal for each type of attribute Table 10 3 Attribute Bindings Binding Token Color Normal Texture Coordinate Coordinate PFGS_OVERALL Yes Yes No No PFGS_PER_PRIM Yes Yes No No PFGS_PER_VERTEX Yes Yes Yes Yes PFGS_OFF Yes Yes Yes No Attribute lists index lists and binding types are all set by pfGSetAttr For FLAT primitives PFGS_FLAT_TRISTRIPS PFGS_FLAT_LINESTRIPS the PFGS_PER_VERTEX binding for normals and colors has slightly different meaning In these cases per vertex colors and normals should not be specified for the first vertex in each line strip or for the first two vertices in each triangle strip since FLAT primitives use the last vertex of each line segment or triangle to compute shading pfGeoSet Operations There are many operations you can perform on pfGeoSets pfDrawGSet draws the indicated pfGeoSet by sending commands and data to the Geometry Pipeline unless IRIS Performer s display list mode is in effect In 327 Chapter 10 libpr Basics 328 display list mode rather than se
587. y In the simplest case pfWindows make creating a graphics application that can run on any Silicon Graphics machine with IRIS GL or OpenGL a snap pfWindows do not limit your ability to configure any part or all of your windowing environment 363 Chapter 10 libpr Basics 364 yourself you can use the libpr pfWindows to manage your GL windows even if you create and configure the actual windows yourself A pfWindow structure is created with pfNewWin It can then be immediately opened with pfOpenWin Example 10 7 shows the most basic pfWindow operations in libpr program to open and clear a pfWindow and swap front and back color buffers Example 10 7 Opening a pfWindow int main void pfWindow win Initialize Performer pfinit pfiInitState NULL Create and open a Window win pfNewWin NULL pfWinName win Hello from IRIS Performer pfOpenWin Rendering loop while 1 Clear to black and max depth pfClear PFCL_COLOR PFCL_DEPTH NULL pfSwapWinBuffers win The pfWindow in Example 10 7 will have the following configuration Window system interface OpenGL windows will be an X window using the OpenGL X interface IRIS GL windows will be pure IRIS GL Screen The pfWindow will open a window on the screen specified by the DISPLAY environment variable or else on screen 0 Windows Position and size The position and size will be undefined and the wi
588. y PFNFY_INFO PFNFY_PRINT doing travGLProf mode d mode 473 Chapter 13 Performance Tuning and Debugging Guidelines for Debugging 474 if mode place glprof tag callbacks trav preFunc cbPutGLProfTag else remove the callbacks trav preFunc cbRmGLProftag MyTraverse node amp trav Use this traverser in a program with a code fragment like that in Example 13 3 Example 13 3 Using the Traverser mode 1 install glprof tag node callbacks mode 0 remove glprof tag node callbacks xf DoGLProfTraversal pfNode scene DBGT_GLPROF mode This section lists some general guidelines to keep in mind when debugging IRIS Performer applications Shared Memory Because malloc doesn t allocate memory until that memory is used core dumps may occur when arenas don t find enough disk space for paging The IRIX kernel can be configured to actually allocate space upon calling malloc but this change is pervasive and has performance ramifications for fork and exec Reconfiguring the kernel is not recommended so be aware that unexplained core dumps can result from inadequate disk space Be sure to initialize pointers to shared memory and all other nonshared global values before IRIS Performer creates the additional processes in the call to pfConfig Values put in global variables initialized after pfConfig will only be visible to the process that set them Guidelines f
589. y pfMalloc Since the size of such data is known pfCopy also works on allocated data Although pfMalloc allocated data behaves in many ways like a pfObject see Nodes in Chapter 5 such data doesn t contain a user data pointer This omission avoids requiring an extra word to be allocated with every piece of pfMalloc data Note All libpr objects are allocated using pfMalloc so you can use pfGetArena pfGetSize and pfFree on all such objects However it s recommended that you use pfDelete instead of pfFree for libpr objects in order to maintain reference count checking Shared Arenas pfInitArenas creates two arenas one for the allocation of shared memory with pfMalloc and one for the allocation of semaphores and locks with usnewlock and usnewsema The arenas are visible to all processes forked after pfInitArenas is called Applications using libpf don t need to explicitly call pfInitArenas since it s invoked by pfInit The shared memory arena can be allocated by memory mapping either swap space dev zero the default or an actual disk file in the directory specified by the environment variable PFTMPDIR The latter requires sufficient disk space for as much of the shared memory arena as will be used and disk files are somewhat slower than swap space in allocating memory By default IRIS Performer creates a large shared memory arena of 256 MB Though this approach makes large numbe
590. y set or globally inherited If all state elements are set locally a pfGeoState becomes a full graphics context that is all state is then defined at the pfGeoState level Global state elements are set with libpr immediate mode routines like pfEnable pfApplyTex pfDecal pfTransparency or by drawing a pfDispList containing these commands with pfDrawDList Local state elements are set by applying a pfGeoState with pfApplyGState note that pfDrawGSet automatically calls pfApplyGState if the pfGeoSet has an attached pfGeoState The state elements applied by a pfGeoState are those modes enables and attributes that are explicitly set on the pfGeoState Note By default all state elements are inherited from the global state Inherited state elements are evaluated faster than values that have been explicitly set While it can be useful to have all state defined at the pfGeoState level it usually makes sense to inherit most state from global default values and then explicitly set only those state elements that are expected to change often Examples of useful global defaults are lighting model lights texture environment and fog Highly variable state is likely to be limited to a small set suchas textures materials and transparency For example if the majority of your database is lighted simply configure and enable lighting at the beginning of your application All pfGeoStates will be lighted except the ones for which you expl
591. yMtl pfTransparency PFTR_ON pfApplyMtl shinyMtl pfEnable PFEN_LIGHTING is equivalent to GeoState state specification pfGeoState gstate pfGStateMode gstate PFSTATE_TRANSPARENCY PFTR_ON pfGStateAttr gstate PFSTATE_FRONTMTL shinyMtl pfGStateMode gstate PFSTATE_ENLIGHTING PF_ON pfApplyGState gstate In addition pfGeoStates have unique state inheritance capabilities that make them very convenient and efficient they provide independence from ordered drawing pfGeoStates are described in the pfGeoState section of this chapter Libpr routines have been designed to produce an efficient structure for managing graphics state You can also set graphics state directly through the GL However libpr will have no record of these settings and will not be able to optimize them and may make incorrect assumptions about current graphics state if the resulting state does not match the libpr record when libpr routines are called Therefore it is best to use the libpr routines whenever possible to change graphics state and to restore libpr state if you go directly through the GL Graphics State The following sections will describe the rendering geometry and state elements in detail There are three types of state elements modes values and attributes Modes are simple settings that take a set of integer values that include values for enabling and disabling the mod
592. ying the major sorting criterion and then an optional list of tokens terminated with the PFSORT_END token that defines a state sorting hierarchy PFSORT_BY_STATE pfGeoSets are sorted first by pfGeoState then by the state elements found between the PFSORT_STATE_BGN and PFSORT_STATE_END tokens for example PFSORT_FRONT_TO_BACK pfGeoSets are sorted by nearest to farthest range from the eyepoint Range is computed from eyepoint to the center of the pfGeoSet s bounding volume 167 Chapter 6 Database Traversal 168 PFSORT_BACK_TO_FRONT pfGeoSets are sorted by farthest to nearest range from the eyepoint Range is computed from eyepoint to the center of the pfGeoSet s bounding volume PFSORT_QUICK A special low cost sorting technique pfGeoSets must fall into a bin whose order is 0 in which case they will be sorted by pfGeoState and drawn immediately This is the default sorting mode for the PFSORT_OPAQUE_BIN bin For example the specification static int sort PFSORT_STATE_BGN PFSTATE_TEXTURE PFSTATE_FRONTMTL PFSORT_STATE_END PFSORT_END pfChanBinSort chan PFSORT_OPAQUE_BIN PFSORT_BY_STATE sort will sort the opaque bin by pfGeoState then by pfTexture then by pfMaterial A pfGeoSet s draw bin may be set directly by the application with pfGSetDrawBin Otherwise IRIS Performer automatically determines if the pfGeoSet belongs in the default
593. ype of interface because they use a mixture of upper and lowercase letters Naming conventions provide for consistency and uniqueness both for routines and symbolic tokens Following similar naming practices in the software that you develop will make it easier for you and others on your team to understand and debug your code Overview of the IRIS Performer Libraries Naming conventions for IRIS Performer are as follows All command and token names whether associated with libpf or libpr are preceded by the letters pf denoting the IRIS Performer library Command and type names are mixed case while token names are uppercase For example pfTexture is a type name and PFTEX_SHARPEN is a token name In type names the part following the pf is usually spelled out in full as is the case with pfTexture but in some cases a shortened form of the word is used For example pfDispList is the name of the display list type Much of IRIS Performer s interface involves setting parameters and retrieving parameter values For the sake of brevity the word Set is omitted from function names so that instead of pfSetMtlColor pfMtlColor is the name of the routine used for setting the color of a pfMaterial Get however is not omitted from the names of routines that get information such as pfGetMtlColor Routine names are constructed by appending a type name to an operation n
594. ze the graphics performance of any application Applications that require real time visuals free running or fixed frame rate display or high performance rendering will benefit from using IRIS Performer IRIS Performer drastically reduces the work required to tune your application s performance General optimizations include the use of highly tuned routines for all performance critical operations and the reorganization of graphics data and operations for faster rendering IRIS Performer also handles Silicon Graphics architecture specific tuning issues for you by selecting the best rendering and multiprocessing modes at run time based on the system configuration IRIS Performer is an integral part of the RealityEngine and Impact visual simulation systems and provides the interface to advanced features available exclusively with RealityEngine graphics IRIS Performer teamed with RealityEngine or Impact provides a sophisticated image generation XXV About This Guide system in a powerful flexible and extensible software environment IRIS Performer is also tuned to operate at peak efficiency on each graphics platform produced by Silicon Graphics you don t need the hardware sophistication of RealityEngine graphics to benefit from IRIS Performer What You Should Know Before Reading This Guide How to Use This Guide xxvi To use IRIS Performer you should be comfortable programming in ANSI C or C You should have a fairly good

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IRIS Performer™ Programmer`s Guide