Berkeley UNIGRAFIX 3.1 — Data Structure and Language
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1. UG 3 UNIGRAFIX s Users Manual UG 3 NAME ug manipulate UNIGRAFIX data structures SYNOPSIS include lt ug h gt cc I UGHOME include L UGHOME lib lug Imat lcompat DESCRIPTION This is a specification for the UG package which implements all manipulations of the internal UNIGRAFIX data structures and the transfer of those data structures to and from text files The grammar of the language can be found in a related document ug 5 Several sample programs are in src packages ug examples A file with fragments showing how to wind around in the topology statements is examples refer Probably the best way to become familiar with this packages is to have a quick read through this manual including the macro section at the end then look over the sample programs and possi bly modify them to gain some familiarity with the data structures In the context of this package a statement is the fundamental object in the data structure In many cases there is a one to one correspondence between lines in the UNIGRAFIX file and statements in the ug data structures but this is notably not true for the topology statements as there are intermediate statement types representing edges and contours which do not appear in the text files Conceptually the user of this pack age should think of the data structure as an ordered branching doubly linked list of statements and a state ment as a sort of variant record which may contain a light2. M4 which concatenate an arbi trary 3 by 3 or 4 by 4 matrix respectively The possibilities for the first letter are s is for scaling t is for translation r is for rotation and m if for mir roring negative scaling with face vertex reversal The possibilities for the second letter are x is for about along the x axis y is for about along the y axis z is for about along the z axis a is for about along all of the axes and v is for about along a particular vector SEE ALSO ug 3 3 1 Release September 20 1994 Page 27
3. 9 3 The UG Library UNIGRAFIX Data Structure and Subroutines Libug is a collection of subroutines for manipulating those polygonal models that can be described with the UNIGRAFIX language The library provides support for reading and writing of the textual format calculating various properties such as the bounding box of a definition manipulating geometry and topol ogy and various other bookkeeping operations Elements of the data structure have a one to one correspondence to elements of the UNIGRAFIX language such as statements transformations etc Main taining the language parser along with the other subroutines means that programs linking with the library will recognize the whole language In particular nested definitions and hierarchical references which are difficult to implement correctly are essentially free Details of the API can be found in the manual page reproduced in an appendix In the following sec tions we will discuss the major design decisions explain how the more difficult features were imple mented and say what should have been done differently 3 1 Implementation Language The ug library was written in a style in C that generously may be called object oriented All data are contained within objects C structures all accesses to the instance data structure fields is through macros there are common messages functions that work on a variety of object types and one level of inheritance is used to fa
4. by looking in each directory in the UGMODELPATH environment variable directories are colon separated If the environment variable is not set then only current directory is used The mode s are the same as fopen 3S Csh 1 s syntax for home directories is understood Writes a file or individual statement to file pointer fp The output file is not closed If indent is greater than or equal to zero it will be used as the initial indentation level and every level of nest ing will be indented by an additional four characters If indent equals 1 no indentation is done FALSE is returned on error BOOL UGset_escape_routine BOOL rp UGstmt UGfile UGstmt UGfile int UGerror_code void void UGprint_error void FILE ROUTINES Page 14 U U ee Gfile Got that When an unrecognized statement is parsed the routine pointed to by rp is called with two parameters an escape UGstmt and the UGfile that the statement appears in This may be the UGfile of a definition nested inside the text file being parsed The default routine will simply add the statement to the file The return value of this function is the previous function so that you can daisy chain them The return value of the escape routine is currently ignored Returns the error code associated with the most recent error At some point this document will spell out what errors can be returned from what routines but for now you can look at the list in
5. hue saturation cfolor _rgb red green blue emission lightness hue saturation emission_rgb red green blue ambient lightness hue saturation ambient_rgb red green blue diffuse lightness hue saturation diffuse_rgb red green blue specular lightness hue saturation specular_rgb red green blue shininess exponent opacity translucency texture fextureID texture deftex id texture_statements end texture_statements texture_statement texture_statement texture_statement t_file filename t_type type gt 3 1 Release September 20 1994 Page 25 UG 5 UNIGRAFIX User s Manual t_size width height num_components t_wrap style t_filter min_filter mag_filter t_scale u_scale v_scale lights deflights id light_statements end light_statements light_statement light_statement light_statement l intensity x y z w materialID camera cam id viewing_options viewing options Viewing_option viewing option viewing option 0g ps vexyz epxyz ud dx dy dz cl hither yon ph minx miny maxx maxy va sx sy fs sx sy fl len include include filename execute execute filename cpp 2 line_no filename escape text escape text contours
6. initial transformation list xforms and incremental transformations list incremental xforms The transformations are listed below The Dentifier is required to make a hierarchical reference to one of the vertices instantiated Hierarchical references to vertices through arrays are formed by prefixing the vertex identifier with the array identifier a colon an integer subscript and a period Subscripts start from zero Examples of array statements and hierarchical vertex references are a rt tetra red tx 10 5 sa 0 75 w origin rt 2 N 1t 0 XY 1t 4 YZ 2 11 Transformations Transformations in instance and array statements start with a dash and a two letter code and may be followed by zero to sixteen parameters as needed The first letter is a s for scaling a t translation a r rota tion a m mirroring or a M for an explicit matrix The second letter is a x for the X axis a y for the Y axis a zz for the Z axis an a for all axes a v for an arbitrary vector a 3 for a 3 by 3 matrix or a 4 for a 4 by 4 matrix Mirroring reorders the vertices in faces to preserve outside ness Mirroring is always about a plane through the origin and the axis or vector is normal to that plane Angles are in degrees All of the legal combinations are given below May 1994 sx scale_factor sy scale_factor sz scale_factor sa scale_factor sv x y z scale_factor tx translation_amount ty translation_amount tz translation_amount ta xyz
7. no mainte nance is done to topology because it is known that this statement is not referred to or because all associated statements will be deleted subsequently Returns FALSE on error Even when safe is FALSE no maintenance is done to topology BOOL UGfree_stmt UGstmt stmt Frees the memory associated with a statement This should be used to get rid of statments that have never been added to files but just used independently In the case of definition statements the statements inside the UG_DEF_BLOCK are not deleted or freed Use UGdelete_file for that purpose 3 1 Release September 20 1994 Page 15 UG 3 UGidx UNIGRAFIX s Users Manual UG 3 UGalloc_ref UGstmt from UGstmt to Creates a reference handle between the statements To is placed on from s reference FROM list and vice versa The UGidx returned is the index in from s FROM list Thus to make a face red assuming you have a color statement pointed to by red and a face statement pointed to by face you would do UG_FACE_COLOR face UGalloc_ref face red To find a face s color state ment you would look at UG_REF_FROM face UG_FACE_COLOR face To find all of the edges that use a given vertex UGstmt vertex edge UGidx 1 for i 0 i lt UG_STMT_TO_COUNTVvertex i edge UG_REF_TO vertex i if UUG_STMT_TYPE edge UG_EDGE_STMT continue UGstmt UGfind_reference const char name int type int IIn_list int Im_cnt UGfile w
8. polyhedra and piecewise linear lines wires can be described The textual format was originally chosen for its simplicity ease of debugging and portability In the past each programmer implemented his own parser to convert from the textual for mat to an internal data structure In this report we describe an application programmer interface API for a UNIGRAFIX binary data structure otherwise known as the ug library or libug The ug library provides cross application consistency for archiving and retrieval of scene data as well as for the API By using the ug library an application automatically tracks changes to the language and the subroutines that manipulate the data structure can be shared between programmers The data structure design and implementation is the work of Michael Natkint and Greg Couch The version described herein contains subsequent additions and modifications by Eric Enderton Kevin Smith and Greg Couch The UNIGRAFIX language described in S quin90 is a subset of what the parser actually recognized and the data structure supported For example nested definitions were already supported at the time of the previous report This version of the language henceforth know as version 3 1 also incorporates language modifications that were made to support the Soda Hall walkthrough project Funkhouser92 Because of those changes the direct correspondence of elements of the data structure to the language and the desire to min
9. ug h and use common sense or just call UGprint_error and exit Prints a text message on stderr describing the most recent error Some UG routines supply UGprint_error with an additional string giving details about the error Gnew_file void Gfile Allocates a file Returns NULL on error Gcopy_file UGfile to UGfile from Makes a brand new identical copy of from To may be NULL in which case it is allocated and returned as the function value NULL return on errors September 20 1994 3 1 Release UG 3 UNIGRAFIX s Users Manual UG 3 BOOL UGdelete_file UGfile uf BOOL safe Recursively delete all statements in uf then uf The caller may set safe to TRUE if memory can be freed without doing all of the maintenance to the topology because it is known that this file is not referred to in other parts of the data structure Safe currently only affects whether memory is freed or not UGfile UGflatten UGfile uf const char prefix BOOL shorten The specified file uf is flattened and the resulting flat file is returned Prefix is prepended to all generated names and may be blank If there is no need for the flattened names to be descriptive pass TRUE for shorten but do use a prefix that will avoid collisions If short names are not used the output names will be of the form prefix_iname_aname index_ _name where iname is an instance name aname is an array name and name is the original name of the statement Flat
10. Berkeley UNIGRAFIX 3 1 Data Structure and Language Gregory S Couch Report No UCB CSD 94 830 May 1994 Computer Science Division EECS University of California Berkeley California 94720 Berkeley UNIGRAFIX 3 1 Data Structure and Language Gregory S Couch Computer Science Division University of California Berkeley ABSTRACT This report describes version 3 1 of the Berkeley UNIGRAFIX scene description language and associated C language data structure and library libug The library pro vides support for reading and writing of scenes calculating various properties such as the bounding box of a definition manipulating geometry and topology and various other bookkeeping operations Maintaining the language parser along with the other subrou tines means that programs linking with the library will recognize the whole language In particular nested definitions and hierarchical references which are difficult to implement correctly are essentially free All previously undocumented features of UNIGRAFIX 3 0 are documented as well as the new features incorporated from the Soda Hall walk through project 1 Introduction The UNIGRAFIX language is a concise textual scene description language intended for the manipula tion and interchange of 3 dimensional polyhedra In addition to polyhedra non manifold objects such as disjoint planar faces with arbitrary holes the building blocks of
11. CAMERA_FILM_SIZEv us float 2 UG_CAMERA_VIEW_ANGLES us float 2 UG_CAMERA_CLIP_PLANES us hither and yon UGextent UG_CAMERA_PORTHOLE us UGllist UG_LIGHT_LLIST us first light in light list UGllist UG_LIGHT_ENDvus end of light list int UG_LLIST_TYPE 1 one of UG_LIGHT_ DIRECT AMBIENT POINT MATvec UG_LLIST_DIR I actually holds a point if type is POINT float UG_LLIST_INTENS I intensity of light UGidx UG_LLIST_COLOR I color of light UGshade UG_COLOR_EMISSION us UGshade UG_COLOR_AMBIENTC us UGshade UG_COLOR_DIFFUSE us UGshade UG_COLOR_SPECULAR us float UG_COLOR_SHININESS us float UG_COLOR_TRANS us UGidx UG_COLOR_TEXTURE us float UG_SHADE_R sh red component of shade float UG_SHADE_G sh green component of shade float UG_SHADE_B sh blue component of shade int UG_TEXTURE_IMAGE_TYPE us char UG_TEXTURE_IMAGE NAME us int UG_TEXTURE_IMAGE_WIDTH us int UG_TEXTURE_IMAGE_HEIGHTC us int UG_TEXTURE_IMAGE_NCOMPONENTS us int UG_TEXTURE_WRAPw us int UG_TEXTURE_MINFILTER us int UG_TEXTURE_MAGFILTER us float UG_TEXTURE_USCALE us float UG_TEXTURE_VSCALE us void UG_TEXTURE_IMAGE us void UG_ESCAPE_TAG us can be used to classify escape statments char UG_ESCAPE_TEXT us char UG_COMMENT_TEXT us int UG_SHADOW_TYPE us UGidx UG_SHADOW_LINK us type of statement being shadowed Macros for contour and edge lists 3 1 Release September 20 1994 Page 23 UG 3 UGidx UGcl
12. FIX statements v1 0 v2 1 v3 1 v4 0 square r r T e aa A r vl v2 v3 v4 a O E EA mha aa S For the square polygonal face we have a list of all of the face s contours each contour has a list of edge directions and edges and each edge has a list of vertices always two Also each of the above types has a list of all references to it vertices have a list of edges to which they belong edges have a list of contours and contours have an associated face Since edges are shared between faces it works well to have them be another statement type and it will help when adding UNICUBIX extensions Since contours are not shared the only advantage of having them be a separate statement is to share implementation code Contours might conceivably be shared among the curved patches from UNICUBIX but it probably only would be use ful for border contours Missing from figure 1 are the links between statements of the same type All statements of the same type in a definition or scene are connected in a doubly linked list Being able to visit all statements in a particular order is important when writing the data structure to a text file because identifiers need to be defined before they are referenced It is also important for flattening instance hierarchies see section May 1994 10 face statement contour list square contour stateme Figure 1 simple square face below on flattening 3 3 Hierarchical R
13. NS AND MACROS Page 20 Currently defined statement types UG_ARRAY_STMT UG_CAMERA_STMT UG_COLOR_STMT UG_COMMENT_STMT UG_CONTOUR_STMT UG_DEF_STMT UG_EDGE_STMT UG_ESCAPE_STMT UG_FACE_STMT UG_INSTANCE_STMT UG_LIGHT_STMT UG_SHADOW_STMT UG_TEXTURE_STMT UG_VERT_STMT UG_WIRE_STMT Currently defined statement flags UG_STMT_SHADOWED UG_VERT_HAS_NORMAL September 20 1994 3 1 Release UG 3 UNIGRAFIX s Users Manual UG_FACE_HAS PLANE EQ UG_DEF_IS_SOLID UG_CAMERA_HAS_ FROM UG_CAMERA_HAS_AT UG_CAMERA_HAS_UP UG_CAMERA_HAS_FLEN UG_CAMERA_HAS_CLIP UG_CAMERA_HAS_ FILM UG_CAMERA_HAS_ ANGLES UG_CAMERA_HAS_PORTHOLE UG_COLOR_HAS_EMISSION UG_COLOR_HAS_AMBIENT UG_COLOR_HAS_DIFFUSE UG_COLOR_HAS_SPECULAR UG_COLOR_HAS_TRANS UG_COLOR_HAS_SHININESS UG_INST_HAS_EXTENT UG_ARRAY_HAS_EXTENT Macro parameter types uf UGfile us UGstmt utf UGtform utl UGtlist cl UGclist el UGelist ll UGllist sh UGshade idx UGidx int type int A UGref is equivalent to a UGstmt Macros for files and statements UGstmt UG_FIRST_TYPE uf type UGstmt UG_LAST_TYPE uf type int UG_FILE_LLN uf UGextent UG_FILE_EXTENT uf UGstmt UG_NEXT_TYPE us UGstmt UG_NEXT_TYPE_SAFE us UGstmt UG_PREV_TYPE us char UG_STMT_NAME us int UG_STMT_TYPE us UGfile UG_STMT_FILE us int UG_STMT_LLN us void UG_STMT_APPL us void UG_STMT_EXTRA us UGref UG_STMT_TO us UGref
14. UG_STMT_FROM Uus int UG_STMT_TO_COUNT Uus int UG_STMT_FROM_COUNT us 3 1 Release September 20 1994 UG 3 first statement of this type last statement of this type Lexical Level Number scope of UGfile extent of UGfile next statement of same type same with guard against NULL us previous statement of same type statement s optional name statement s type UGfile statement belongs to LLN of UGfile statement belongs to application data not touched by library used for instance traversal available otherwise references TO this statement references FROM this statement number of references TO this statement number of references FROM this statement Page 21 UG 3 UNIGRAFIX s Users Manual UG 3 Reference macros UGref UG_REF_TO us idx UGref UG_REF_FROM us idx Flag macros BOOL UG_STMT_FLAG_SETv us flag test if statement flag is set void UG_STMT_SET_FLAG Uus flag set statement flag void UG_STMT_CLEAR_FLAG us flag clear statement flag Loop macros UG_FOR_ALL_STMTS us uf type visit all statements in uf UG_FOR_ALL_STMTS_SAFE us uf type tmp_us UG_FOR_ALL_STMTS_REALLY us uf type tmp_us even shadow statements UG_FOR_ALL_TYPE us uf type UG_FOR_ALL_TYPE_SAFE us uf type tmp_us UG_FOR_ALL_TFORMS utf utl UG_FOR_ALL_TFORMS_SAFE utf utl tmp_utf Use the SAFE versions of the macros whenever you might be deleting the object pointed to by the loop variable The
15. _amount tv x y z amount rx angle ry angle rz angle rv x y z angle MV x yZ M3 a M4 a 00 01 202 120 f 11 212 920 or 22 00 701 02 103 1011 212 213 220 ar ao 123 930 931 932 933 2 12 Color Statements Usage Usage c olor ZD lightness hue saturation translucency c olor _rgb ID red green blue translucency textureID The color statement is a shorthand for material definition that sets both the ambient color and the dif fuse color to arguments identifiers the given color value See the sections on materials below for a description of the various The ZDentifier shares the same namespace as that of the material definition statement 2 13 Material Definition Statement Usage defmat D material statement end A material definition may only contain material statements they are listed in the following section The Dentifier provides a unique reference to the material 2 13 1 Material Statements Usage Usage Usage Usage Usage Usage Usage Usage Usage Usage Usage Usage Usage c olor lightness hue saturation c olor _rgb red green blue emission lightness hue saturation emission_rgb red green blue ambient lightness hue saturation ambient_rgb red green blue diffuse lightness hue saturation diffuse_rgb red green blue specular lightness hue saturation specular_rgb red green blue shininess exponent opacity translucency texture te
16. a vertex etc To see what data is in the variant part of each statement look at the macro listings at the end of the manual It is also possible to loop through all of the statements of any one type in a file All references between statements are mediated through reference lists Every statement has a TO list which contains pointers to all statements which refer to it and a FROM list which contains pointers to all statements to which it refers FROM lists always contain at least one entry which is a pointer to a NULL statement for example a face with no color will have it s FACE_COLOR index set to refer to the NULL reference in it s FROM list Statments in text files which begin with a are read verbatim into a UG_ESCAPE_STMT until the matching is found See UGset_escape_routine Hierarchical references from one statement to another are allowed and are kept in shadow statements See UGfind_reference UGfind_vertex_coords This is currently used only for vertices but should be usable for other types The routines here hide the fact that there are shadow statements fairly well but one must be aware of them T O ROUTINES UGfile UGread UGfile uf FILE fp const char filename int first_line UGfile UGread_str UGfile uf char str const char filename int first_line Gfile Gread_lIls UGfile uf FILE fp int IIn_list int lIn_cnt const char filename int first_line Ce Gfile Gread_str_lls UG
17. contour contour contour C vertexID vertexID tforms tform tform tform SX amt sy amt sz amt sa amt sv x y z amt tx amt ty amt tz amt ta amt tv x y z amt rx amt ry amt rz amt rv x y z amt mx my mz ma mv x yz M3 all al2 al3 a21 a22 a23 a31 a32 a33 M 4 all al2 al3 al4 a21 a22 a23 a24 a31 a32 a33 a34 a41 a42 a43 a44 UG 5 UNIGRAFIX uses a right handed coordinate system with the vertices in the outermost contour of a face given in counter clockwise order VIEWING OPTIONS Page 26 Each viewing option may only be given once projective transformation type og set orthographic mode the default ps sets perspective mode World to Eye Coordinates vc sets the view center the look at point ep sets the eye point the look from point ud sets the up direction a vector not a point Eye Coordinates to Canonical View Volume va sets the viewing angles fs sets the film size fl sets the focal length Only two out of va fs and va should be set cl sets the hither and yon clipping planes in view volume September 20 1994 3 1 Release UG 5 UNIGRAFIX User s Manual UG 5 coordinates ph sets the porthole in the viewport to render expressed in normalized device coordinates TRANSFORMS All transformations follow a regular two letter code except for M3 and
18. ctor out the common code for handling each UNIGRAFIX statement type A decomposition of the code within the library would naturally separate the code on object oriented boundaries and would cleanly map into an object oriented language If C had been more mature when the ug library was writ ten it would have been a much better implementation language The reason for taking the pseudo object oriented approach was to isolate implementation details from the interface and it has successfully done so 3 2 Data Structure This UNIGRAFIX data structure is similar to the standard winged edge data structure Hanrahan82 but differs in many important ways A winged edge data structure describes a single closed shape and requires that an edge have at most two faces connected to it UNIGRAFIX can describe non manifold struc tures such as multiple closed shapes sharing vertices edges and faces For example in UNIGRAFIX a fan of rectangles that share a common edge will also share that edge in the data structure And in UNIGRAFIX faces may have holes contours in them while in a winged edge data structure they may not The con tours make algorithms written for the UNIGRAFIX data structure slightly more complicated than ones writ ten for a winged edge data structure which is a trade off for the greater expressive power of the UNI GRAFIX data structure Figure 1 shows the data structure for an uncolored square that is generated by the following UNI GRA
19. d and ending with a semicolon The exception to this rule is extension statements which are enclosed within parenthesis Identifiers consist of letters digits underscore sharp sign and colons They must not start with a digit and case is significant Identifiers are unique within each statement type All literal text is in boldface text that must be substituted is in italic Square brackets denote optional fields and three periods denote optional repetition of the preceding identifier or group ing All numbers are real i e digits optionally followed by fractional part decimal point and digits optionally followed by an exponent an E a plus or minus sign and digits the leading digits are optional if there is a fractional part White space is used to separate tokens that would be otherwise unseparable 2 2 Vertex Statement Usage v ID x y z w materialID All object coordinates in UNIGRAFIX appear in vertex statements The Dentifier uniquely identifies the vertex within a scene or definition x y and z are the 3 dimensional coordinates of the vertex The homogeneous coordinate w may be given as well The optional materiallDentifier selects the material properties of the vertex Vertices must be specified before they are referenced Vertices can be referred to hierarchically through instance chains See the description of the instance and array statements for exam ples of hierarchical refere
20. d the instance path The instance and array statements are recursively descended after the setup callback function has been called If a shadowed statement sets its UG_STMT_EXTRA field then that value is automatically propagated to the UG_STMT_EXTRA field of the appropriate shadow statement After all of the statements have been visited once each statement is visited again and the cleanup callback function is called During cleanup the UG_STMT_EXTRA field is free d unless the save_extra flag has been set The last step is to call the optional pop_matrix callback function STATEMENT SPECIFIC ROUTINES MATreal UGfind_vertex_coords UGstmt vertex Returns a pointer to the coordinate values of a particular vertex If the vertex pointer is a shadow hierarchical reference then the values returned are the result of transforming the actual vertex coordinates by the concatenation of the transforms of instances in the reference See UG_VERT_POINT_SAFE macro BOOL UGcompute_camera UGfile ugfile UGstmt cam float y_over_x Computes the camera matrices represented by the data described in the camera statement Attempts are made to fill in reasonable default values for viewing options which are not set For example the ugfile s extent is used to compute the look from and look at points if they were not set in the camera statement The default up direction is the y axis The default viewing angle is 30 degrees The default focal length and film
21. dentity 3 1 Release September 20 1994 Page 17 UG 3 UNIGRAFIX s Users Manual UG 3 transform and clear the matrix OK flags EXTENTS Typically you will use the EXTENT macros instead of using the following routines because bounding box extents are maintained automatically for instance array and definitions statements UGextent UGnew_extent UGextent pext Allocates an extent saves it in pext and return it Gextent Gtform_extent UGextent out const UGextent in MATmatrix matrix aia Transforms the extent by the given non projective matrix place the result in out and return it Gextent Gmerge_extent UGextent in_out const UGextent in ef Combines two extents place the result back into the first one and return it Gextent Gclear_extent UGextent pext ee Clears an extent by setting the minimum values to the largest positive floating point value and maximun values to the negative of the minimum values void UGclear_stmt_extent UGstmt Recursively clears the extent for the given instance array or definition statement and all definitions instances arrays that refer to it ROUTINES FOR MANIPULATING TOPOLOGY Page 18 Edge lists UGelist s are doubly circularly linked lists each element of which contains a reference see UGalloc_ref to an edge and a direction A contour statement has a UGelist as it s only data item The references in the UGelist are indices int
22. e the UGMODELPATH environment variable is consulted for a list of directories colon separated in which to look for the file If the UGMODELPATH environment variable is not set then only the current directory is checked 2 20 Execute Statement Usage execute UNIX command The execute statement causes the textual output from the given UNIX command to be incorporated into the scene at the current location The PATH environment variable is consulted for a list of directories colon separated to look in for the given program 2 21 C Preprocessor Support Usage line number quoted filename A line beginning with a denotes a C preprocessor synchronizing line for supporting error messag ing in the presence of include directives See the UNIX manual page for cpp May 1994 2 22 Comments Usage anything nesting is OK Comments may be placed anywhere that white space may occur This includes almost any possible place except within identifiers or numbers Comments are surrounded by curly braces and and may contain any character as long as curly braces are balanced For example This is a legal comment This is also a more complicated legal using nested s comment 2 23 Extension Escape Statement Usage anything with balanced parenthesis Extension statements are provided as a mechanism for preprocessors to augment scene descriptions such as the BUMP Oakland87 animation package May 1994
23. eferences to Vertices Usually an edge points directly to its associated vertices When there is a hierarchical reference to a vertex the vertex statement is replaced by a shadow statement Conceptually the shadow statement pre tends it is the actual vertex and then uses the instantiation path to return modified coordinate and normal values Transforming the shadowed vertex information is computationally expensive in comparison to just copying the coordinate or normal values but it is sometimes the best way to describe linkages between instances a wheels wheel rz 45 2 rz 90 tx 3 w link wheels 0 v1 wheels 1 v1 Figure 2 train wheels Figure 2 demonstrates why hierarchical references are useful with a train wheel example The two wheels are linked with a wire that makes hierarchical references to a vertex in each wheel 3 4 Expanding Instances Flattening a Scene The flattening algorithm is heavily dependent upon a partial ordering of the UNIGRAFIX statement types in the ug library The partial ordering is derived from the graph expressing which statement types make references to other statement types Statements that are referred to need to be flattened first If a new May 1994 statement type is introduced it needs to placed in the correct order relative the other statement types The current ordering is as follows textures materials lights definitions instances arrays shadows vertices edges contours w
24. es Alternatives are separated by vertical bars By default all variables are real numbers with the following exceptions size and line_no are integers text and filename are arbitrary strings id is a string consisting of upper and lowercase chars digits colon underscore _ and sharp but not beginning with a digit materialID vertexID definitionID light sID and texturelD are id s of the appropriate statement type Left curly brace and right curly brace are comment delimiters and may be nested White space is always ignored except to separate fields file statements statements statement statement statement vertex wire face definition instance array color material texture lights camera include execute cpp escape vertex v id x y z w materiallID wire w id contours materialID face f id contours materialID definition def id solid statements end instance i id C definitionID materialID lightsID tforms array a id C definitionID materialID lightsID tforms size tforms color c olor id lightness hue saturation translucency c olor _rgb id red green blue translucency textureID material defmat id material_statements end material_ statements material_statement material_statement material_ statement c olor lightness
25. file uf char tr int IIn_list int In_cnt const char filename int first_line ee These functions read a scene from either the file pointer fp or the string str and build the internal data structure a UGfile that represents it This representation is sufficient to allow the file to be written back in nearly identical form to the original depending on the changes made by the calling program If the parameter uf equals NULL a structure is allocated and returned as the value of the function Otherwise the new UGstmt s are appended NULL is returned on errors 3 1 Release September 20 1994 Page 13 UG 3 FILE UGmodel_open const char filename const char mode BOOL UGwrite UGfile uf int indent FILE fp BOOL UGwrite_stmt UGstmt us int indent FILE fp UNIGRAFIX s Users Manual UG 3 The filename and first_line arguments are for setting the initial values used for error messages If a statement being read needs to refer to objects defined outside of uf e g if you are reading the inside of a definition and the statement refers to colors or definitions outside the definition s scope then you need to use UGread_lIls or UGread_str_lls to provide the parser with a lexical level number stack for UGfind_reference See UGfind_reference below Files included via UNIGRAFIX s include mechanism are found by looking in the directories in the UGMODELPATH environment variable Opens the given filename
26. filters and 5 is a mipmap trilinear filter using precompute filters The mag filter specifies which filter to use when one texel of the texture corresponds to more than one pixel on the screen mag nify 0 is a point filter and 1 is a bilinear filter The style tells how the texture behaves at its boundarys 0 if it repeats default and 1 if it clamps The u scale and v scale tell the number of times to replicate the texture within the selected face if the style is set to repeat in the u and v directions respectively 2 16 Light Definition Statement Usage deflights ZD light statement end A lights definition may only contain light statements that are listed in the following section The IDentifier provides a unique reference to the set of lights 2 17 Light Statement Usage l intensity x y z w materialID The light statement places a light source in the scene The intensity specifies the brightness of the light source The materialIDentifier selects a material that colors the light for smarter renderers the default is to use only the intensity and ignore a light s color The light source defaults to be an ambient May 1994 light source unless x y and z are given in which case it is a directional light with x y and z being the direc tional vector it need not be normalized If w is given and non zero then it is a point light source 2 18 Camera Statement Usage cam JD viewing option 5 The camera statemen
27. here Returns a pointer to the UGstmt that defines the specified name of the given type Returns NULL either on error or if the name is not found LIn_list is an array of lexical level numbers in which to look for the statement and IIn_ent is the number of entries in IIn_list For most statement types only the last scope IIn_list IIn_count 1 on the list is searched For open scope state ments defs colors and lights if there are statements by the same name in several of the scopes in lln list the last one is used i e the innermost scope Note that the lln for a UGfile can be obtained using the UG_FILE_LLN macro Also note that if you are looking in only one scope say scope x it is simplest to pass lln list amp x lln_ cnt 1 You might want to use UGfind_by_name instead see below A name may also be prefixed by a series of separated instance and array names Arrays must be subscripted with an followed by an element number In this case the scope should be the scope in which the first instance or array name is defined If this is done a UG_SHADOW_STMT statement will be added to the file where The where parameter should therefore point to the UGfile where a reference to the named object will exist This parameter may be NULL if you know that there are no periods in the name This allows flattening to take place properly The return value from this function will be the pointer to the shadow statement Shadow state
28. homas J LeBlanc A Symbol Table Abstraction to Implement Languages with Explicit Scope Control IEEE Transactions on Software Engineering 9 1 8 12 January 1983 Foley90 James D Foley Andries van Dam Steven K Feiner John F Hughes Computer Graphics Prin ciples and Practice Addison Wesley Reading MA 1990 Funkhouser92 Thomas Funkhouser Carlo H S quin Seth Teller Management of Large Amounts of Data in Interactive Building Walkthroughs Proceedings of the 1992 ACM SIGGRAPH Symposium on Interactive 3D Graphics Boston MA 1992 Hanrahan82 P Hanrahan Creating Volume Models from Edge Vertex Graphs Computer Graphics 16 3 77 84 July 1982 Neider93 Jackie Neider Tom Davis Mason Woo OpenGL Progamming Guide Addison Wesley Read ing MA 1993 Oakland87 Steven Anders Oakland BUMP a Motion Description and Animation Package Master s Report U C Berkeley September 1987 S quin84 Carlo H S quin The UNIGRAFIX 2 System Proceedings National Computer Graphics Association Conference Anaheim CA May 1984 S quin90 Carlo H S quin Kevin P Smith Introduction to the Berkeley UNIGRAFIX Tools Version 3 0 Technical Report UCB CSD 90 606 Berkeley California November 1990 Shirman90 Leon A Shirman Construction of Smooth Curves and Surfaces from Polyhedral Models Technical Report UCB CSD 90 602 Berkeley California December 1990 May 1994
29. ier might be found Local identifiers override identifiers with the same name in outer scopes How LLN s work to improve symbol table performance is described in Cook83 The application programmer rarely uses the fact that there is a full symbol table available as most applications implicitly work with scene descriptions that have no definitions in them i e flat scenes One exception is the bump animation package Oakland87 which uses scoped language extensions to implement its features There is one implementation detail in the hash table used for the symbol table code that needs explaining By design the hash table uses the linked list chaining method to reduce lookup time for sym bols while parsing The UG_symbol structure is the linked list element that is used to maintain the chain and the UGstmt structure points back to the UG_symbol in the hash chain that references the UGstmt The back pointer is used to remove the entry from the symbol table when a named statement is deleted Because the hash chain is a singly linked list the UG_symbol is never reclaimed thus causing a small memory leak each time a named statement is deleted Should this be a problem it will be possible to reclaim the space the next time that hash chain is searched May 1994 12 5 References Bui Toung75 Phong Bui Toung Illumination for Computer Generated Pictures Communications of the ACM 18 6 311 317 June 1975 Cook83 Robert P Cook T
30. imize the number of documents needed to learn the UNIGRAFIX language a detailed description fol lows that incorporates parts of the previous description S quin84 Section 2 describes the UNIGRAFIX language and section 3 describes the data structure and library Michael Natkin worked for Professor S quin at U C Berkeley from February through April of 1987 May 1994 2 The UNIGRAFIX Language Elements The following is a description of each statement type in the UNIGRAFIX language Statements can be loosely categorized into five categories geometry vertices topology faces wires hierarchy definitions instances arrays rendering information material properties textures lights cameras and other include execute C preprocessor comments extension As a convenience for past users the differ ences from the previous description version 3 0 are highlighted with a sidebar along the right margin The synopsis of changes include 1 color has been generalized to material properties 2 hierarchical references to vertices are allowed 3 there are more transformation types and 4 a statement extension mechanism has been implemented For completeness the UNICUBIX Shirman90 extensions for nameable edges borders and patches are described here even though they have yet not been incorporated into the ug library yet 2 1 Syntax A UNIGRAFIX scene description consists of a sequence of statements each starting with a keywor
31. ints to the edge This new elist has its dir all set and contour s FROM list is updated to point to the new edge In other words the elist that is returned is all ready to be spliced into contour UGstmt UGmake_contour UGstmt vlist BOOL face UGfile uf UGstmt ptr Vlist is an array of pointers to vertex and or shadow UGstmts terminated by a NULL Creates and returns a contour UGstmt whose elist contains an edge between each adjacent pair of vertices If face is TRUE an additional edge is created from the last vertex to the first vertex The contour is added to uf before ptr BOOL UGmake_contours UGstmt stmt UGfile uf UGstmt vlist UGstmt ptr This is not exactly symmetrical with the previous routine so read carefully Vlist is now a list of verts of the following form NULL v1 v2 v3 NULL v4 v5 NULL NULL NULL Each null separated piece is passed to make_contour and the result is spliced on to the end of stmt s clist Stmt should be either a face or a wire statement This is quite special purpose but sometimes it is convenient All of the new contours will be put before ptr in uf New clist entries are created for each new contour and they are spliced on to stmt s clist at the end void UGhls_to_shade float h float 1 float s UGshade color Convert a HLS color triple to RGB color void UGshade_to_hls UGshade color float h float 1 float s Convert a RGB color to a HLS triple DEFINITIO
32. ires faces cameras and extensions When the UNICUBIX statement types are incor porated the edge and border types will be either immediately before or after edges and patches will be either immediately before or after faces Shadow statements are used as place holders for hierarchical references to vertices As each instance is expanded the hierarchical name of the instance is cached A vertex has a flag stating whether or not it is shadowed When a shadowed vertex is transformed all of the shadow statements that refer to it are exam ined to see if the name used to refer to the vertex matches the current hierarchical name i e if the shadow statement s name is a suffix of the current hierarchical name This handles multiple hierarchical refer ences through multiple levels of instantiation There is a computational cost of maintaining the current hierarchical name which is wasteful in scenes that don t have any hierarchical references Luckily the overhead is fairly low and is proportional to the instance tree complexity of scene which should be at least an order of magnitue smaller than the number of primitives duplicated vertices edges wires faces etc 3 5 Nested Definitions Each definition has its own lexical scope and is assigned a unique lexical level number an LLN A LLN is never reused during a program An explicit list of visible LLN s is maintained while parsing the UNIGRAFIX language to track in which scopes an identif
33. ist UGclist UGidx int UGelist UGelist UNIGRAFIX s Users Manual UG 3 UG_CLIST_CONTOUR cl UG_CLIST_NEXT cl UG_CLIST_PREV cl UG_ELIST_EDGE el UG_ELIST_DIR el UG_ELIST_NEXT el UG_ELIST_PREV el Macros for handling transforms char 3 MATreal 16 int UG_TFORM_TYPE utf UG_TFORM_PARAMS utf UG_TFORM_NUM_PARAMS lt utf circularly doubly linked index 0 or 1 into EDGE_VERTS of first vertex Circularly doubly linked MATmatrix UG_TFORM_MAT utf maintained for you BOOL UG_TFORM_MAT_OK utf clear if you change a tform after UGadd_tform ing it UGtform UG_TFORM_NEXT utf BOOL UG_TFORM_MIRROR utf TRUE if contours should reverse MATmatrix UG_TLIST_MAT utl maintained for you BOOL UG_TLIST_MAT_OKc utl clear this if you change any tform UGtform UG_TLIST_TFORMSv utl BOOL UG_TLIST_MIRROR utl ENVIRONMENT UGMODELPATH a colon separated list directories to search for include files SEE ALSO mat 3 compat 3 AUTHOR Page 24 Michael Natkin February through April 1987 Greg Couch September 20 1994 3 1 Release UG 5 UNIGRAFIX User s Manual UG 5 UG ug UNIGRAFIX file format DESCRIPTION The following is a pseudo BNF description of the UNIGRAFIX file format Literals are in boldface except for punctuation which is enclosed in single quotes lt Variables are are in italics Optional parts are enclosed in square brackets Zero or more repetitions are enclosed in curly brac
34. ments are skipped by the loop macros available to the applications programmer UGstmt UGfind_by_name const char name int type UGfile uf MATmatrix mat int Returns a pointer to the UGstmt that defines the specified name of the give type Returns NULL either on error or if the name is not found Only looks in the given UGfile uf and if it is a hierarchical reference there are no side effects i e it will never return a shadow statement see UGfind_reference The resulting pointer is not usable for adding as a reference in the data struc ture but is useful for checking for existence and for extracting values If a non null value is passed in for the matrix argument it is filled in with the transformation matrix of the found state ment from the given UGfile i e from hierarchical references UGwalk_inst_hier UGfile ugfile MATmatrix matrix const UGwalk_funcs funcs Page 16 Recursively descends the instance hierarchy starting with the given transformation matrix The funcs argument contains callback function pointers for all statement that you are interested in For each instance the optional push_matrix callback function is called Then in the statement type September 20 1994 3 1 Release UG 3 UNIGRAFIX s Users Manual UG 3 order the setup callback function is called with the current statement current transformation matrix whether or not the statement should be mirrored the current color the current lights an
35. nces to vertices Examples of vertices are v origin 0 0 0 v upper_right 3 5 10 3 4e2 2 3 Wire Statement Usage w ID vertex1 vertexN materialID The wire statement describes piecewise linear lines Each group of vertices must have at least two elements The materialIDentifier selects the material properties of the wire Examples of wires are w bristle v34 v94 brown w closed_loop v1 v2 v3 v4 v5 v6 v7 v1 w origin instance upper_right w tetra It rt top back rt back It top red May 1994 The last example creates a red wire frame of a tetrahedron 2 4 Edge Statements Usage el id vertex1 vertex2 Usage ec id vertex vertex2 xl yl zl x2 y2 z2 The curved edge differs from the linear edge by specifying the two interior control points x1 y1 z1 and x2 y2 z2 of a cubic bezier curve Typically a surface is discontinuous at an edge Not imple mented yet 2 5 Border Statements Usage bl id vertex1 vertex2 Usage be id vertex vertex2 x1 yl zl x2 y2 z2 Borders are edges where the tangent vector across the edge must be continuous The linear border is analogous to the linear edge and the curved border is analogous to the curved edge Not implemented yet 2 6 Face Statement Usage f ID vertexl vertex2 vertexN materialID The face statement describes a planar polygon that may have holes The first vertex group must have at least three elements and the o
36. ng section The IDentifier provides a unique reference to the texture 2 15 Texture Statements Usage t_file filename Usage t_type type Usage t_size width height num components Usage t_wrap style Usage t_filter min filter mag filter Usage t_scale u scale v scale The texture statements may appear at most once and in any order inside a texture definition The tex ture statements correspond to the information needed for an OpenGL renderer see Neider93 for a more detailed description The t_file and t_size statements are required The filename is the name of the file that contains the texture The type is an integer that gives the texture file format i e O for an SGI image file format and 1 for the tiff format unsupported Each pixel in the texture file corresponds to a texel in the texture The width height and num components fields give the width in texels height in texels and the number of components in the texture A 1 component texture file is used as an intensity map a 2 com ponent file is used as an intensity alpha map a 3 component file is used as RGB map and 4 component file is used as a RGBA map The min filter specifies which filter to use when more than one texel of the texture corresponds to a pixel on the screen minification O is a point filter 1 is a bilinear filter 2 is a select a point from a precomputed filter 3 is a linear filter using precomputed filters 4 is a bilinear filter using precomputed
37. o a contour s FROM list Keep in mind that for a face contour the edge that connects the last vertex to the first must still be explicit wire contours are circularly linked also Similarly faces and wires have UGclist s which are lists of references to contours It is always up to you to be sure that edge lists are consistent i e that the last vertex of one edge matches the first vertex of the next edge keeping in mind the ELIST_DIRection The clist manipulation routines are a subset of the elist routines if you ignore all references to direction and replace all UGelist s with UGclist s new and old are now faces or wires UGelist UGalloc_elist void UGclist UGalloc_clist void Allocates a UGelist circularly links it to itself and returns a pointer to it You must use this rou tine for all allocation of elists because all of the following routines assume and maintain circular linked ness for all UGelists UGelist UGsplice_elist UGelist pos UGelist new UGelist head UGclist UGsplice_clist UGclist pos UGclist new UGclist head Inserts the list new after pos Pos is normally an element of the elist pointed to by head If pos is NULL then head is set to point to new Head will typically be the address of a UG_CONTOUR_ELIST The return value is always head If new is NULL nothing is done September 20 1994 3 1 Release UG 3 UNIGRAFIX s Users Manual UG 3 UGelist UGunsplice_elist UGeli
38. size are chosen to make sure the whole scene is visible Use the UG_CAMERA flags to control which viewing options are considered set UGllist UGalloc_llist void Allocates the data structure for a single light a light list of one element void UGadd_llist UGllist llist UGstmt stmt int loc UGllist ptr Adds the light Ilist to the given UG_LIGHT_STMT statement Loc and ptr have the same mean ing as in UGadd_stmt UG_ARB is not currently implemented however void UGfree_llist UGIlist beg Release the memory used for the light list TRANSFORMATIONS BOOL UGadd_tform UGtform tform UGtlist tlist int loc UGtform ptr Adds the transform tform to the transformation list tlist Loc and ptr have the same meaning as in UGadd_stmt UG_ARB is not currently implemented however When adding a transforma tion there is no need to compute the matrix simply fill in the transformation name and parame ters using the UG_TFORM macros If you change part of a transformation after it has been added you must set the UG_TFORM_MAT_OK and UG_TLIST_MAT_OK flags to FALSE to make sure that the matrix will be recomputed the next time it is asked for For M3 and M4 transformations you may set the UG_TFORM_MIRROR macro if you want contours to be reversed This is set automatically for m transforms BOOL UGdelete_tform UGtform tform UGtlist tlist Removes tform from tlist Not implemented Of course you can always set it to an i
39. st beg UGelist end UGelist head UGclist UGunsplice_clist UGclist beg UGclist end UGclist head Separates the list pointed to by head into two parts One piece will run from beg to end and the remaining piece will still be pointed to head The return value of the function is a pointer to the list begun by beg If head is somewhere between beg and end inclusively it is set to point to any element remaining in the initial list or NULL if the whole list is unspliced from itself Beg and end may be equal Gelist Gkill_elist UGelist beg UGelist end UGelist head ee Gclist Gkill_clist UGclist beg UGclist end UGclist head Exe Same as UGunsplice_elist but elements that are unspliced are then freed Return value is head Gelist Gmirror_elist UGelist el E E Reverses the order of all edges in el in place and returns a pointer to the elist entry that starts with the same vertex as el did Essentially all of the ELIST_NEXT and ELIST_PREV pointers are swapped and the ELIST_DIR s are toggled Try it on paper Gelist Gduplicate_elist UGelist el ee Gclist Gduplicate_clist UGclist el ee Makes a new copy of el and returns a pointer to it Gelist Gconvert_elist UGelist el UGstmt new UGstmt old ae Gclist Gconvert_clist UGclist el UGstmt new UGstmt old ec You didn t start to think of elist s as pointing to edges did you Remember they con
40. statements in the current definition over riding ones in outer levels while all other references must be to statements in the current definition An example of a definition statement defining a tetrahedron is May 1994 def tetra solid vXZ 1 1 l v YZ 1 11 vXY 1 1 1 vN 1 1 1 fxyz YZ XZ XY fx NXY XZ fy XYN YZ fz XZ YZN end 2 9 Instance Statement Usage i ID defID materialID lightsID xforms The instance statement instantiates the named definition def Dentifier optionally of a given material materiallDentifier optionally just lit by one set of lights lightsIDentifier and optionally transformed to a different position and or orientation xforms The possible transformations are listed below The Dentifier is required to make a hierarchical reference to one of the vertices instantiated Hierarchical references to vertices through instances are formed by prefixing the vertex identifier with the instance identifier and a period Examples of instance statements and hierarchical vertex references are ired_tetra tetra red tv 10 5 20 1 0 i tetra sa 5 w red_tetra N origin 2 10 Array Statement Usage a ID defID materiallD lightsID xforms count incremental xforms The array statement instantiates the named definition def Dentifier count times optionally of a given material materialIDentifier optionally just lit by one set of lights lights Dentifier and optionally with an
41. t places a camera in the scene A renderer will default to using the last camera statement in a scene unless a camera identifier is given as an argument If no camera statement is present in a scene an implicit camera is created that views all elements in the scene The many viewing options are Projection style 0g set orthographic mode the default ps set perspective mode World to Eye Coordinates vex yz set the view center the look at point ep xyz set the eye point the look from point ud x yz set the up direction not a point Eye Coordinates to Canonical View Volume Only two of the va fs and fl need be present to fully specify the eye to canonical view transformation va x angle y angle set the viewing angles fs x size y size set the film size fl length set the focal length cl hither yon set the hither and yon clipping planes in view volume coordi nates ph left right bottom top set the porthole in the viewport to render expressed in normalized device coordinates 1 0 to 1 0 in clusive 2 19 Include Statement Usage include filename The include statement allows the creation of libraries of scene elements The text in the given filename incorporated into the scene at the current location If the filename is an absolute path starts with a slash or starts with a tilde then it is read from the given location Otherwis
42. tain UGidx s that are relative to a contour s FROM reference list This routine changes each element of el so that it points to the same edges in new as it used to in old adding new elements to new s refer ence FROM list and taking them out of old s It also removes the references to old in the el s edges s TO list So a typical operation might be to unsplice some edges from one contour convert the elist and splice it into another contour UGelist UGreplace_edge_in_all UGstmt edge int dir UGelist elist UGstmt ref_contour For every contour which uses edge we replace edge with elist Elist is defined relative to ref_contour Dir is the relative direction of elist to the verts in edge so if edge contains the verts A and B and elist is AX YB dir should equal zero ROUTINES FOR CREATING EDGES AND CONTOURS EASILY UGstmt UGmake_edge UGstmt v1 UGstmt v2 int dir UGfile uf UGstmt ptr If an edge already exists connecting v1 and v2 it is returned and dir is set appropriately 0 if the existing edge lists v1 first 1 if it lists v2 first If not a new edge UGstmt is created before ptr in 3 1 Release September 20 1994 Page 19 UG 3 COLOR UNIGRAFIX s Users Manual UG 3 uf dir is set to 0 and the new statement pointer is returned UGelist UGmake_edge_for_contour UGstmt v1 UGstmt v2 UGfile uf UGstmt contour UGstmt ptr Does a UGmake_edge and creates an elist for contour that po
43. ten ing is considerably faster with short names Also note that objects that are referred to by hierarch ical referencing will retain their full names even if shorten is TRUE STATEMENT ROUTINES UGstmt UGalloc_stmt int type Allocates the data structure for a statement of type type defined below Returns NULL if there are problems BOOL UGadd_stmt UGstmt stmt int loc UGstmt ptr UGfile uf BOOL nameok Adds stmt to uf If loc is UG_BEG or UG_END stmt is put at the beginning or the end of the file respectively If loc is UG_ARB stmt is placed before the statement pointed to by ptr or if ptr is NULL at the end of the file The parameter nameok may be set to TRUE if it is known that the name of the new statement does not conflict with any other statement in this file in order to reduce the processing time FALSE is returned on error UGstmt UGcopy_stmt_data UGstmt to UGstmt from Copies all of the data associated with from to to The statement name and the reference lists are not copied but elements of the data which point into the reference list are To may be NULL in which case it is allocated and returned Chances are you should be using UGcopy_file instead of just the statement data BOOL UGdelete_stmt UGstmt stmt BOOL safe Removes the statement from the data structure and hopefully does the right thing if this affects the topology of an object If safe is TRUE then the statement can be freed as well and
44. tmp_ variables are used by the loop but contain no information for the user Macros specific to given statement types MATpoint UG_VERT_POINT us MATpoint UG_VERT_POINT_SAFE us follows shadow statements MATvec UG_VERT_NORMALA us MATvec UG_VERT_NORMAL_SAFE us follows shadow statements UGidx UG_VERT_COLOR us UGidx UG_VERT_COLOR_SAFE us follows shadow statements UGidx 2 UG_EDGE_VERTS us UGelist UG_CONTOUR_ELIST us UGclist UG_FACE_CLIST us MATvec UG_FACE_PLANE_EQ us UGidx UG_FACE_COLOR us UGidx UG_FACE_LIGHTS us float UG_FACE_LIGHTNESS us UGclist UG_WIRE_CLIST us UGidx UG_WIRE_COLOR us float UG_WIRE_LIGHTNESS lt us UGfile UG_DEF_BLOCK us UGidx UG_INSTANCE_DEF us UGidx UG_INSTANCE_COLOR Uus UGidx UG_INSTANCE_LIGHTS us UGtlist UG_INSTANCE_TLIST us UGextent UG_INSTANCE_EXTENT us UGidx UG_ARRAY_DEF us UGidx UG_ARRAY_COLOR us UGidx UG_ARRAY_LIGHTS us int UG_ARRAY_SIZE us UGtform UG_ARRAY_INIT_TLIST us UGtform UG_ARRAY_INC_TLIST us Page 22 September 20 1994 3 1 Release UG 3 UNIGRAFIX s Users Manual UGextent UG_ARRAY_EXTENT us BOOL UG_CAMERA_TYPE us one of UG_CAMERA_ PERS ORTHO MATmatrix UG_CAMERA_VIEW_MAT us MATmatrix UG_CAMERA_INV_VIEW_MAT us MATmatrix UG_CAMERA_PERS_MATuus MATmatrix UG_CAMERA_INV_PERS_MAT us MATpoint UG_CAMERA_FROM us MATpoint UG_CAMERA_ATv us MATvec UG_CAMERA_UP us float UG_CAMERA_FOCAL_LENGTH us UG 3 float 2 UG_
45. uter side of the face is determined by their counter clockwise order Each vertex group is automatically closed The material Dentifier selects the material properties of the face Any additional vertex groups describe holes in the face and may be degenerate i e one or two vertices The vertices of holes must be given in clockwise order holes of holes i e islands in counter clockwise order etc Examples of face statements are f square Il Ir ur ul f holey_triangle c1 c2 c3 h1 h3 h2 2 7 Patch Statement Usage p ZD vertex1 vertex2 vertex3 vertex4 materialID The patch statement describes either a triangular or a quadrilateral patch Not implemented yet 2 8 Definition statement Usage def ID solid arbitrary UNIGRAFIX statement end Definitions provide a method for abstracting part of a scene for multiple instantiations in different orientations and materials The Dentifier uniquely identifies the definition within a scene or definition The solid keyword is a hint for renderers so they may cull backfaces if the material is opaque A definition is not visible unless it is instantiated with an instance or array statement Definitions provide a scope for identifiers for example a vertex could have the same identifier in dif ferent definitions Definitions may be arbitrarily nested Identifier references to definition and material statements may reference statements in outer nesting levels with
46. xtureID Materials have four color components emission ambient diffuse specular a specular shininess an opacity translucency and an associated texture Each of the color components can be specified with either the RGB color model or the HLS color model Foley90 In the RGB _rgb suffix versions of the material May 1994 statements red green and blue should all range from zero to one The HLS versions of the material state ments uses a double cone color model lightness should fall in the range from zero black to one white with saturated colors having a lightness value of one half hue should be a number between zero and 360 and follows a standard color wheel red 0 yellow 60 green 120 cyan 180 blue 240 magenta 300 saturation should fall in the range from zero gray scale to one fully saturated The default hue and saturation are undefined gray and fully saturated respectively The specular shininess exponent defaults to zero off and is the same as the exponent in the Phong lighting model Bui Toung75 Translucency ranges from zero opaque to one translucent and is used by some renderers to imple ment semi transparent objects By default all materials are opaque The texture Dentifier is a reference to a texture defined below 2 14 Texture Definition Statement Usage deftex ID texture statement end A texture definition may only contain texture statements that are listed in the followi
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