Documentation - YASRT Raytracer
Contents
1. input_name string output_type string output_name string attenuation_type string shadow _type string radius double light_samples integer camera_index integer aperture double focal_point vector or focal_length float camera_samples integer background color display integer integer jpeg_quality integer jitter string antialiasing string aa_distance integer haze_color color haze_factor float Note that this file contains only one section enclosed in curly brackets Everything else in the file will be either ignored or cause a parsing error Here is a description for each parameter of this structure 1 2 input_name this keyword is followed by a string that specifies the name of the input 3DS file The filename has to contain the 3ds extension attenuation_type this keyword is common to all light sources present in the 3DS scene It allows specifying which light attenuation model to use during rendering Possible values are none no light attenuation will be used d the attenuation will be proportional to the inverse of the distance from the light d2 the attenuation will be proportional to the inverse of the square of the distance from the light shadow_type this keyword is common to all light sources present in the 3DS scene It allows specifying which type of shadow to use during rendering Possible values are sharp the shadows cast in the scene will be sharp2. and its default value is black 0 0 0 haze_factor this parameter is followed by a float value that specifies the importance of the haze effect in the scene High values lead to thick haze A value of 0 means that the haze effect is not activated This parameter is not mandatory and its default value is 0 The following example shows the declaration on a complete settings structure settings display 1024 768 output_type jpeg output_name myScene jitter no jpeg_quality 90 antialiasing adaptive aa_distance 32 background lt 0 0 0 gt haze_color lt 111 gt haze_factor 0 05 Camera The camera section of the YASRT scripting language defines the different parameters of the camera of the scene The syntax is the following camera position look_at up projection_type fov ratio aperture focal_point camera_samples vector vector vector string float float float vector or integer or focal_length float samples integer Here is a description for each parameter of this structure 1 position this keyword is followed by a vector that specifies the position of the viewer This parameter is mandatory and there is no default value 2 look_at this keyword is followed by a vector that specifies where the viewer is looking at in the virtual world This parameter is mandatory and there is no default value 10 11 Up this keyword is followed by a vector t
3. at which the scene is in focus This parameter is not mandatory its default value is 10 It can be used in place of focal_point Both cannot be specified focal_point this keyword is followed by a vector that specifies the point at which the scene is in focus This parameter is not mandatory It can be used in place of focal_length Both cannot be specified camera_samples this keyword is followed by an integer that specifies the number of extra rays to trace when depth of field is activated Large values will slow rendering times but lead to better visual results This parameter is not mandatory its default value is 16 samples this keyword is the same as camera_samples The following example shows the declaration of a camera camera position lt 10 10 10 gt look_at lt 0 0 0 gt up lt 0 0 1 gt fov 60 ratio 1 33333 aperture 0 15 focal_length 11 samples 16 Here is an example of a scene using the depth of field effect The following example shows a scene using the fisheye projection Lights The light section of the YASRT scripting language defines the different parameters of the lights of the scene The syntax is the following light position target color attenuation_type shadow_type radius min_angle max_angle light_samples vector vector color string string double double double integer or samples integer Here is a descrip
4. To start the rendering phase just tap on the screen Linux To install YASRT on Linux please do the following 1 Download YASRT from its official Web Site http www yasrt org 2 Download the Linux version for your platform Intel only currently 3 Uncompress the archive downloaded into a directory of your choice usr local yasrt for example by doing the following Open a Shell window Create the installation directory e g mkdir usr local yasrt Copy the archive downloaded cp yasrtXXXX tgz usr local yasrt Change the local directory to that created e g cd usr local yasrt Uncompress the archive e g gunzip d yasrtXXXX tgz ES f Untar the archive e g tar xvf yasrtXXXX tar 4 Add the YASRT directory to your path environment variable DEC UNIX See the Linux Installation Instructions for more details HP UX See the Linux Installation Instructions for more details AIX See the Linux Installation Instructions for more details FreeBSD See the Linux Installation Instructions for more details Solaris See the Linux Installation Instructions for more details Trix See the Linux Installation Instructions for more details BeOS See the Linux Installation Instructions for more details MacOS X See the Linux Installation Instructions for more details Tutorial This section is a tutorial that walks the user through the main features of YASRT This section is not meant to replace the full user s refere
5. field of view thus giving the impression of zooming out Reduce the camera field of view thus giving the impression of zooming in a Activate de activate the animation of the scene rotation around the target point of the camera A Same as a b Make a screenshot of the screen to a BMP file auto incremented B Same as b c Dump the objects and the settings of the scene in the specified inc and yst file C Make a screenshot of the screen to a TGA file auto incremented d Activate de activate the creation of the successive anti aliased frames of an entire animation of the scene in PNG format Same as d Switch to full screen mode Same as f mia 0 Make a screenshot of the screen to a PPM file auto incremented Same as i Anti alias the view on the screen Same as j a Re Make a screenshot of the screen to a JPG file auto incremented platform dependent Same as k Switch to normal resolution Same as n Dump the objects of the scene in the specified inc file loz ja x Make a screenshot of the screen to a PNG file auto incremented platform dependent Same as p Exit the program Same as q Dump the settings of the scene in the specified yst file cm O Make a screenshot of the screen to a TIFF file auto incremented platform dependent Same as t Cycle between wire frame pl
6. if the contribution of subsequent rays traced is not significant enough the process is stopped This process is then applied to all pixels of the image What is radiosity Radiosity is a complex algorithm used to simulate the global lighting of a scene Since raytracing uses local optical laws i e laws that are applied at a single point without taking into account its surrounding environment it cannot take into account complex light transfer mechanisms that appear in the real world An algorithm was developed to take into account these mechanisms Radiosity is a view independent algorithm that can be used in conjunction with raytracing to render realistic pictures Without going into details let s just say that this algorithm takes into account the effect such as When no light directly reaches a part of a scene it is rendered totally flat with the raytracing technique By using radiosity this part of the scene won t be flat but resemble what s found in the real world When bright surfaces red for example are placed near a white wall this wall will have a faint red aspect for example Though not supported in this current version a global illumination algorithm will be added to YASRT in order to simulate the global illumination effects of a scene to render The first implementation will probably be Path Tracing the second one Photon Mapping Current Features The following list describes what has been implemented in the curr
7. smooth the shadows cast in the scene will be smooth This effect is also referred to as penumbra The output results are more realistic at the cost of longer rendering times radius this keyword specifies the smoothness of the smooth shadows of the scene Larger values lead to smoother shadows The next keyword must be then used in order to avoid aliasing effects light_samples this keyword specifies the number of additional rays to trace when smooth shadows are activated Larger values lead to smoother shadows and less aliasing effects at the cost of longer rendering times camera_index the 3DS file format support multiple cameras in the scene In order to use one given camera in the scene this keyword can be used aperture this keyword allows activating the depth of field effect The effect can be amplified by using large values at the cost of rendering effects 8 focal_length this keyword is followed by a float that specifies the distance at which the scene is in focus This parameter is not mandatory its default value is 10 It can be used in place of focal_point Both cannot be specified 9 focal_point this keyword is followed by a vector that specifies the point at which the scene is in focus This parameter is not mandatory It can be used in place of focal_length Both cannot be specified 10 camera_samples this keyword allows controlling the number of additional rays that are traced when depth of field is activated Large v
8. the declaration of a smooth triangle smooth_triangle vertex lt 1 5 1 5 0 gt normal lt 0 01 gt vertex lt 1 5 1 5 0 gt normal lt 0 01 gt vertex lt 2 2 0 gt normal lt 0 01 gt Here is such a smooth triangle The following picture shows the use of a large amount of smooth triangles in a scene 3DS file courtesy of Ludovic Bridant Ring The syntax is a follows ring center vector normal vector internal_radius float external_radius float Here is a description for each parameter of this structure 1 center this keyword is followed by a vector that specifies the center of the ring This parameter is mandatory and there is no default value for it 2 normal this keyword is followed by a vector that specifies the normal of the ring This parameter is mandatory and there is no default value for it 3 internal_radius this keyword is followed by a float that specifies the value of the internal radius This parameter is mandatory and there is no default value for it 4 external_radius this keyword is followed by a float that specifies the value of the external radius This parameter is mandatory and there is no default value for it The following example shows the declaration of a ring ring center lt 0 0 0 gt normal lt 001 gt internal_radius 1 external_radius 2 Here is this ring rendered Disc The syntax is a follo
9. SRT can take advantage of multi processor machines to speed up rendering times support for 2 4 and 8 threads currently p Support for direct output onto the screen platform dependant 4 Scripting language to describe the scene to render Environment settings haze background color etc Camera settings position direction field of view depth of field etc Lights descriptions Primitives descriptions Surface descriptions Declaration of colors to re use them throughout the scene Inclusion of external files to re use existing objects Single line and multiple line comments Output settings anti aliasing parameters output file settings etc 5 Different image file formats supported LOs BMP PPM TGA JPEG platform dependant TIFF platform dependant PNG platform dependant Support for renderings of large amount of primitives Native support of the 3DS file format platform dependant 8 Auxiliary tools to preview and convert the 3DS file format to the YASRT ASCII format platform dependant The following table summarizes the different technical features supported on the different platforms targeted by YASRT Platform Supported Features Comments Win32 Intel Multi threading Primary target BMP PPM TGA TIFF JPEG amp PNG Native 3DS file support 3DS file converter and pre viewer Linux Intel Multi threading Secondary target BMP PPM TGA TIFF JPEG amp PNG Native 3DS file suppo
10. YASRT Raytracer YASRT Version 0 1 Beta 14 User s Documentation Last Updated October 10th 2002 Copyright 2000 2002 Emmanuel Viale Abstract This document is the user s manual for the YASRT Raytracer It describes what YASRT is and what it s not It walks the reader through a tutorial that shows the main features of the program A full documentation on the YASRT language is also given All tools that are part of the package are also described in this document Table of Contents todas di do ad 4 Whats Tirada tocas dds 4 Whats r ytracing iia 4 W Ha tS radiosity narrando rra 5 Current Fett iii ii lod aid 5 F t re Features moc air eara ea aaa aan aaaea a tatty arab aaa 8 Installation Notes suite 9 WINdOW Se nceann dio 9 PockeiP Canina aia 9 A ya Sawada AAO TA A REA N 9 DEC UND dana data 10 HP UX O A Tia aia 10 DIANA AAA AAA RA AAA 10 FreeBSD A A A ation dss Coss 10 NS 10 o salsa aydci P SU U go ae gad up Ava a Ue seta i Dela 10 BOSA AAA ee eS 10 MacOS Avid dla 10 TOA A e e e ei 11 Y ASRT language Lea tines ni 11 A O 11 A A 11 o scawecis sas casishasaa vasnls ciuthcosrtoy cheat aty acai iatbean sets a usiner eee sees cncoetahte seu esteaga tse 11 A O 11 DIES AAA A RADA AA A A iT eadads Maaes 11 YASRT Command Line Options ois es e eta 12 Input and Output File OPOS 4 taeda SD ee 12 Me RST ssh tt hoc tal id as iach dates atletas 12 Output lead AA A eran oa ee TONS 12 Raya Options a a a eee aero eeNs 13 A
11. ain and point rendering mode lt e Switch between flat and shaded model Future Tools More tools will be added along the evolution of YASRT
12. alues will lead to smoother results and less aliasing effects at the cost of longer rendering times 11 display see previous section 12 output_type see previous section 13 output_name see previous section 14 jpeg_quality see previous section 15 jitter see previous section 16 antialiasing see previous section 17 aa_distance see previous section 18 background see previous section 19 haze_color see previous section 20 haze_factor see previous section The following example shows the declaration on a complete settings structure input_name test3ds 3ds output_type tga output_name test3ds display 800 600 aa_type adaptive aa_distance 16 The rest of this section explains features of the language that can be used only with the YASRT scripting language not the 3DS file format support Environment The settings section of the YASRT scripting language defines different directives concerning the rendering of the current scene The syntax is the following settings display integer integer output_type string output_name string jitter string Jpeg_quality integer antialiasing string aa_distance integer background color haze_color color haze_factor float Here is a description for each parameter of this structure 1 display defines the resolution of the final image to render The keyword is followed by two integers the width and the heig
13. arse the file called myscene yst Note that this is the only required switch to render a particular scene All other switches override parameters describe in the settings section of the YASRT scripting language see below Output File 1 Output File Name The output file name can be changed by using the o or output switch followed by the name of the output file without any file extension YASRT will automatically append the correct file extension based on the output file type For example C YASRT yasrt exe i myscene yst o mysenefirstrender on Windows platforms Or yasrt i myscene yst o mysenefirstrender on UNIX platforms In this case the scene will be rendered to the myscenefirstrender image file The extension of this file depends on the output format specified in the settings section of the script the default being BMP Output File Type The output file type can be changed by using the appropriate switch Here is the list of possible types BMP by using the bmp or bmp switch TGA by using the tga or tga switch PPM by using the ppm or ppm switch PNG by using the png or png switch not supported on all platforms JPEG by using the jpg or jpeg switch not supported on all platforms TIFF by using the tif or tiff switch not supported on all platforms Screen output by using the screen or screen switch not supported on all platforms For exampl
14. bjects or libraries of colors for example What follows is an example of inclusion inside a script include mycolors inc include myobjects inc The mycolors inc and myobjects inc files are valid ASCII files containing Y ASRT objects color declarations and so forth Data types Before describing all the primitives supported by YASRT it is important to present the different types of data that are manipulated by the raytracer YASRT supports different types of entities This section describes these entities and gives examples on how to use them These will serve as the basis for primitive declarations Integers Integers are used by YASRT to determine integer numbers Integer values can be positive negative or null depending on the context in which they are used What follows is an example of the use of an integer in a YASRT script settings display 800 600 This example shows how to define the output format of the image to render The first integer represents the width of the image the second integer represents the height of this image see below for more details Floats Floats are used by YASRT to determine floating point numbers Float values can be positive negative or null depending on the context in which they are used What follows is an example of the use of a float in a YASRT script settings haze_factor 0 345 This example shows how to define the c
15. d by a float that specifies the value of the radius of the cone at the cap This parameter is mandatory and there is no default value for it The following example shows an example of cone centered around the origin lt 0 0 0 gt and with a unit radius 1 that extends along the z axis on 5 units lt 0 0 5 gt and has a radius of 0 5 at the cap cone base lt 0 0 1 gt cap lt 0 0 1 gt base_radius 1 cap_radius 0 5 Here is this cone rendered Cylinder The syntax is a follows cylinder base vector cap vector radius float Here is a description for each parameter of this structure 1 base this keyword is followed by a vector that specifies the base of the cylinder This parameter is mandatory and there is no default value for it 2 cap this keyword is followed by a vector that specifies the cap of the cylinder This parameter is mandatory and there is no default value for it 3 radius this keyword is followed by a float that specifies the value of the radius of the cylinder This parameter is mandatory and there is no default value for it The following example shows an example of cylinder centered around the origin lt 0 0 0 gt and with a unit radius 1 that extends along the z axis on 5 units lt 0 0 5 gt cylinder base lt 0 0 1 gt cap lt 0 01 gt radius 1 Here is this cylinder rendered Tools This section descr
16. different parameters of the surface of an object Currently YASRT only supports some texturing features like reflection refraction and specular reflection Future versions will support more advanced texturing models procedural texturing including texture mapping bump mapping etc Once a texture is declared in a script it is applied to all the objects that follow in the script To change a texture simply declare a new one it will be used by all following objects within the script The syntax is the following surface color color ambient float diffuse float brilliance float specular float roughness float reflection float reflection_type string reflection_radius float reflection_samples integer refraction float refraction_index float Here is a description for each parameter of this structure 1 color this keyword is followed by a color that specifies the intrinsic color of the object This color will be used by the raytracing engine along with the following parameters in the structure to determine the exact color at a point on the surface of an object ambient this keyword is followed by a float that specifies the ambient factor of the object The ambient term in raytracing is used to simulate the effect of global illumination in a scene Since standard raytracing cannot determine the exact value of this term it is simulated by using a constant value The value can range from 0 0 t
17. dvanced OPUONS ira il ill d ais 14 Mal Tra daa 15 DS File Support 15 Priority Queue SIZE nar 16 Language Star 17 PU PES SANS AAA 17 Inputtiles uu 17 A eenia eers eE ER E A S GE UESN 17 File inelusions ui ia 18 Data PES A A tt tdi 18 TARO ROS chess OS 18 Hot id e od dos malas 18 Colts 19 Cs A o nn la i iia i Sadan eat cB adea aidai 19 SOULS sah 5 sas NE NE EE E EE E oeoeaa aay ETEN S 20 variable declaro cant ii Gtia 20 9DS Fle SUD POE ota to iia 21 o AAA o a ey ccc Bea Lavi Raed wile sha dapec eas co Beats 23 CAMINA E EEE 26 Lies apli cdas 29 LOUIS TR 33 LAA VES is asi edies coats tach Meas Sau vaste basta beet Mat Spatnes orm a stele ia 37 o E E sametetses 37 A ai soonnda was otdonacsn cua web ndowe a ea ane ES aa a a Ea aeii 38 A a a a 40 o onen e e a a a e a ia 41 Smooth triangle pate ina eani ai 43 RNE RA ANA A 45 DISC scwcd A AS A A A AAA A a tees 47 CO RRA de 48 A ie AB a ida lop a R TO EA E R AEREE LRE 50 TOO ANA dan EINE AEE E EE dean so O 52 The SDS file conversion utility SdUS2y Stic occavtices tein dcsesdien diiniita dad 52 The 3DS file pre viewer and converter gl3ds2yst oonicicnccicicnnnnnonnnncconicncancnonono 52 Future Tools rn EA 56 Introduction This section presents the YASRT Raytracer The main features are listed along with current and future features The section ends with installation notes for the different platforms supported What is it YASRT is a raytracing program It us
18. e C YASRT yasrt exe i myscene yst o mysenefirstrender ppm on Windows platforms Or yasrt i myscene yst o mysenefirstrender ppm on UNIX platforms In this case the scene will be rendered to the myscenefirstrender ppm image file Raytracing Options This section describes the different command line options that apply to raytracing It is possible for example to change the jittering and anti aliasing options through the use of command line switches Future versions will add other features such as the possibility to adjust the quality of the rendering The anti aliasing switches are the following ones 1 For no anti aliasing use the aan or aanone 2 For quick anti aliasing use the aag or aaquick 3 For adaptive anti aliasing use the aaa or aaadaptive followed by an integer representing the threshold value used by this algorithm Low values give best results at the cost of the time spent to render the scene Jittering can be activated by using the j or jitter switch Jittering introduce random effects in the way rays are shot in the world The effect is to reduce the amount of aliasing in the final image To specify the size of the final image from the command line several switches are available e ror resolution this switch is followed by two positive integers representing the width and height of the image to render e w or width this switch is followed by a positive integer represent
19. ent version of YASRT e Raytracing features Ha gt N 9 Different camera models flat and fisheye Advanced camera model with depth of field effect when objects are not in the focus of the camera they appear blurry like on photographs Lights with realistic distance attenuation the intensity of the light diminishes with the distance from which an object is lit in the scene Light attenuation models are 1 d 1 d This feature can be turned off if needed Point lights and spot lights supported All lights can cast soft shadows penumbra for more realistic pictures Support for different surface properties Phong lighting model Intrinsic color Ambient color Diffuse color Specular reflection Transparency Reflection sharp and fuzzy Refraction Simulation of haze Different primitives supported Sphere Cone Plane Polygon Triangle Smooth triangle patch Ring Cylinder Distributed or stochastic raytracing penumbra fuzzy reflection depth of field 10 Acceleration technique Kay amp Kajiya to speed up rendering times Technical features 1 Supported on several platforms Windows 9x Me 2000 and XP Intel platform and Windows NT Intel and Alpha platforms Linux Intel platform BeOS Intel platform MacOS X PowerPC platform Trix Solaris SPARC platform AIX HPUX PocketPC 3 0 and 2002 ARM SH3 and MIPS 2 Multi threading YA
20. es the raytracing algorithm to generate realistic pictures from textual descriptions of three dimensional scenes It uses the metaphor of photography to achieve this goal The photographer the user of the program uses a camera the program to shoot render photographs two dimensional pictures of the surrounding world text description of a three dimensional scene By using advanced raytracing techniques YASRT can simulate realistic optical phenomena such as reflection objects can be reflected in mirrors refraction object can be seen through other transparent objects shadows are cast when the light is blocked by one or more objects objects have different surface properties etc YASRT is a program taking one or more files text or binary files depending on the platform for input and generates a picture binary file of the scene described in these files A description language allows artists to describe the scene to be rendered Alternatively it is possible to use different tools to export scenes from different 3D authoring tools These tools are described later in this document On some platforms YASRT also supports the 3D Studio file format internally Note that the support of the format is limited to the features present in YASRT for example image mapping is not yet supported in YASRT What is raytracing Raytracing is an algorithm that can be used to produce photo realistic pictures of three dimensional virtual worlds
21. f every single ray against every single primitive When the number of primitives in the scene is large thousands of objects the program might bail printing an error message YASRT is out of space Please use the pqs or pqsize switch to increase the priority queue size In this case the priority queue size of the algorithm must be increased the default value is 128 by using the pqs or the pgsize switch followed by the new value of the size of the priority queue For example C YASRT yasrt exe i myscene yst pqs 170 on Windows platforms Or yasrt i myscene yst pqs 170 on Unix platforms YASRT will use priority queues with a size of 170 elements maximum Note it is highly recommended to leave the default value of this parameter This command line switch should be used only when YASRT bails with the error message corresponding to an insufficient priority queue size Language Syntax This section thoroughly describes the YASRT language used to describe 3d scenes This section is the core of the Y ASRT reference manual File types This section describes the different types of files handled by YASRT Input files Y ASRT reads textual files as input files for scene description files ASCII files These files can be created using any text editor provided that they are saved as ASCII files with no extra formatting Example of text editors include Notepad Windows WordPad Windows be sure to save
22. g processor time is sliced and divided among the different tasks to execute The multi threaded version of YASRT uses threads to render the different parts of an image in parallel By default the workload involved in rendering an image is equally divided between the threads of execution It is possible to increase that number YASRT can support two four or eight threads of execution to speedup rendering times The default number of threads is 2 To change the default number of threads simply use the t or the thread switch followed by 2 4 or 8 For example C YASRT yasrtmt exe i myscene yst t 8 on Windows platforms Or yasrtmt i myscene yst t 8 on Unix platforms In this case the scene will be rendered by eight parallel threads 3DS File Support On some platforms YASRT supports the rendering of 3D Studio binary files without needing the conversion of this type of files beforehand In this case two additional switches are available the 3ds or the 3ds switch followed by the name of the YASRT configuration file see next section and the c or the camera switch followed by an integer representing which camera to use to render the scene 3DS files can have several cameras defined For example C YASRT yasrt exe 3ds myscene yst on Windows platforms Or yasrt 3ds myscene yst on Unix platforms Priority Queue Size YASRT uses a complex technique to avoid testing the intersection o
23. hat defines what vector should be considered as the altitude For left handed systems the value is lt 0 1 0 gt for right handed systems it is lt 0 0 1 gt This parameter is not mandatory its default value is lt 0 0 1 gt YASRT is right handed by default projection_type this keyword is followed by a string that specifies the type of projection to use Possible values are flat standard 3d projection will be used fisheye a fisheye projection will be used fov this keyword is followed by a float that specifies the field of view in degrees Small values will lead to an effect of zooming in close up while large values will lead to an effect of zooming out This parameter is not mandatory its default value is 45 ratio this keyword is followed by a float that specifies the ratio of the final image to render Normal computer screens have a ratio of 4 3 Standard resolutions also use this ratio 640x480 1024x768 etc This parameter is not mandatory its default value is 4 3 aperture this keyword is followed by a float that specifies the importance of the effect of depth of field This effect simulates that seen in real photographs where objects out of focus will appear blurry Large values will lead to accentuating this effect This parameter is not mandatory its default value is 0 0 no depth of field effect by default focal_length this keyword is followed by a float that specifies the distance
24. he output results are more realistic at the cost of longer rendering times 5 radius this keyword specifies the smoothness of the smooth shadows of the scene Larger values lead to smoother shadows The next keyword must be then used in order to avoid aliasing effects 6 light_samples or samples this keyword specifies the number of additional rays to trace when smooth shadows are activated Larger values lead to smoother shadows and less aliasing effects at the cost of longer rendering times target this keyword is used to specify the target point of a spot light 8 min_angle this keyword is used to specify the angle of the spot light under which the scene is fully lit Its value must be lower than that of the max_angle parameter see below 9 max_angle this keyword is used to specify the angle of the spot light under which the light diminishes A point in the scene at an angle greater than this value will not be lit by the corresponding spot light J The following diagram illustrates the different parameters of a spot light position min_angle max_angle The following example is a light located at lt 10 10 10 gt and of a white color light position lt 10 10 10 gt color 111 The following example shows a scene using two spot lights The following example shows a scene using soft shadows penumbra Textures The surface section of the YASRT scripting language defines the
25. he same angle as the incident light Note 10 11 12 that reflection increases rendering times since new rays must be traced from the intersection point on the surface reflection_type this parameter can be either sharp or fuzzy sharp will use sharp reflections for the current surface standard model whereas fuzzy will activate fuzzy reflection In this case the two following keywords must be specified reflection_radius this parameter specifies how fuzzy the reflections can be Large values will lead to more fuzzy reflections at the cost of more aliasing effects In order to smooth the appearance of very fuzzy reflections the following parameter must be adjusted reflection_samples this parameter controls the number of ray samples that are reflected for each incoming ray The larger the value the better the results at the cost of longer rendering times Note that this parameter must be set according to the value of the previous parameter refraction this keyword is followed by a float that controls the amount of light that is refracted by the surface The value can range from 0 0 to 1 0 It can be thought of as the transparency of the object to which it is applied Note that refraction increases rendering times since new rays must be traced from the intersection point on the surface The default value is 0 0 no refraction refraction_index this keyword is followed by a float that specifies the index of refraction of the
26. he script the color can also be part of an include file as described before For more details on the declare directive see below Vectors YASRT makes extensive uses of vectors in many of its structures A vector is defined by three floating point components representing in order of appearance the x component the y component and the z component What follows is an example of the use of a vector in a YASRT script plane normal lt 0 0 1 gt distance 0 5 This example shows how to declare a plane The normal vector represents the normal of the plane for more details on the plane structure see below Strings YASRT uses strings in different elements of its scripting languages generally textual directives Strings are enclosed between double quotes What follows is an example of the use of a string in a YASRT script settings output_type bmp This example shows how to specify the BMP file format for the output image For more details on the output_type directive see below Variable declarations To easily re use different elements of the YASRT language within the same scene or to share these elements between different scenes it is possible to declare elements colors floats integer values primitives textures etc NOTE the current version of YASRT only supports declaration for colors Future versions of YASRT will support declarations for other elemen
27. ht of the image both in pixels The display parameter is not mandatory the default values are 320 width by 240 height output_type defines the type of the output The keyword is followed by a string specifying the format of the output image The value of this parameter depends on the platform and the support of image file types See the release notes for more information on the formats supported for a particular platform Possible values are bmp to specify the BMP file format tga to specify the TGA file format ppm to specify the PPM file format jpeg to specify the JPEG file format not all platforms tiff to specify the TIFF file format not all platforms png to specify the PNG file format not all platforms screen to render directly onto the screen no image will be saved by specifying this option not all platforms Note that this option will slow down renderings on Windows platforms rendering time are at least 50 bigger in future versions this will be fixed This parameter is mandatory and there is no default output file format 3 jpeg_quality this keyword is followed by an integer Itis supported only by versions of YASRT with JPEG support The integer specifies the level of compression of the output image it lies between 0 and 100 Low values correspond to lower file size high compression high values correspond to higher file size low com
28. ibes the different tools bundled with YASRT Depending on the platforms these tools may or may not be present Future versions will include more tools in the package The 3DS file conversion utility 3ds2yst The 3ds2yst utility is a command line program It must be called from a shell UNIX or a command prompt windows It is currently not supported on all platforms However it can be used to convert and then render a scene that was modeled in an external package The 3DS file can then be converted to a YASRT ASCII file and rendered on a platform where the 3DS file format is not natively supported The following summarizes how to the program can be called Usage 3ds2yst options Options i input string specify the file to open with 3ds extension o output string specify the output file no extension c camera integer specify the initial camera to use t triangle triangles as output default is patches help this help message Example 3ds2yst i car 3ds o cartest The 3DS file pre viewer and converter gl3ds2yst The gl3ds2yst utility is a command line program It must be called from a shell UNIX or a command prompt windows It is currently not supported on all platforms It is very similar to 3ds2yst but adds also the possibility to preview the 3DS scene before converting it Additionally it can be used to take screenshots from the OpenGL rendering window with anti aliasing in different file f
29. ing the width of the image to render e hor height this switch is followed by a positive integer representing the height of the image to render For example C YASRT yasrt exe i myscene yst aaa 24 on Windows platforms Or yasrt i myscene yst aaa 24 on Unix platforms In this case the scene will be rendered using adaptive anti aliasing with 24 as the adaptive distance For more information on anti aliasing and jittering please refer to the Environment section of the User s Reference part of this document Advanced Options This section describes the different advanced command line options available Some of these options should be used with care as they change the way YASRT works internally the value of the priority queue size for instance Multi Threading Some versions of YASRT support multi threading Multi threading is a technique by which a program can execute several tasks in parallel On machines with only one processor even though the program appears to be doing several things at the same time only one task is being executed at a given time On machines with more than one processor and depending on the underlying operating system the program will actually run its different tasks across the different processors available If the program is executing more tasks than the number of processors the different tasks will be shared among these processors This sharing mechanism is also known as time slicin
30. nce section see below but is just an introduction to the main features of the Raytracer YASRT language features Environment Camera Lights Textures Primitives THIS SECTION TO BE ADDED YASRT Command Line Options YASRT is a command line program except for the pocketPC version which features a simple user interface This means that it must be started from a shell or executed from an external program This section describes all the command line switches available to the program Note that the command line options supersede the different directives given in the scene description file given as input This allows having a set of directives for the final version of the scene while still quickly allowing experimenting new features with shorter rendering times by overriding this set of directives Some command line switches are available on some platforms only while others are common to all platforms To quickly obtain a list of the different options supported for a given platform simply type yasrt in a shell window Input and Output File Options This section describes the different command line options that apply to input and output files Input File The scene to render is specified using the i or input switch followed by the name of the input file For example C YASRT yasrt exe i myscene yst on Windows platforms Or yasrt i myscene yst on UNIX platforms In this case YASRT will try to p
31. ne normal vector distance float Here is a description for each parameter of this structure 1 normal this keyword is followed by a vector that specifies the normal of the plane This parameter is mandatory and there is no default value for it 2 distance this keyword is followed by a float that specifies the value of the distance of the plane from the origin This parameter is mandatory and there is no default value for it The following example shows the declaration of the x y plane at one unit down on the z axis i e which equation is z 1 plane normal lt 0 01 gt distance 1 By adding this declaration to the previous scene the plane is added to the scene Polygon The syntax is a follows polygon integer vertex vector vertex vector vertex vector vertex vector vertex vector Here is a description for each parameter of this structure 1 The first parameter of the polygon structure that specifies the number of vertices This parameter is mandatory it must be placed as the first entry of the structure and there is no default value for it The number of vertices must be greater than three For three vertices use the triangle structure instead 2 vertex this keyword is followed by a vector that specifies one the vertices of the polygon The vertices must be declared in the counter clockwise order The following example shows the decla
32. o 1 0 Typical values range from 0 1 to 0 3 Large value will render the object glowing diffuse this keyword is followed by a float that specifies the amount of light that is reflected off the surface at the exact same angle it came in This term is also known as diffuse reflection A value of 0 5 means for example that 50 of the light seen from the object comes directly from the different light sources of the scene The rest is absorbed by the object brilliance this keyword is followed by a float that controls the way light interacts with the object depending on the incident angle High values will make the object look more metallic specular this keyword is followed by a float that controls the way highlights are generated when the light bounces off the objects surface Simply put highlights are the bright spots that appear on objects that depend upon viewing angle and illumination angle The specular term can range from 0 0 to 1 0 0 0 meaning no highlights while 1 0 means total saturation of the highlight roughness this keyword is followed by a float that controls the size of the highlight Large values will give large highlights while small values will give very smooth and small highlight reflection this keyword is followed by a float that controls the amount of light that is reflected off the surface of the object The value can range from 0 0 no reflection to 1 0 total reflection The light is reflected off the surface with t
33. object Typical values are 1 0 for air 1 33 for water 1 5 for glass and 2 4 for diamond The default value is 1 0 air What follows is the example of simple surface declaration surface color 0 419 0 556 0 137 ambient 0 1 diffuse 0 75 brilliance 1 0 specular 0 3 roughness 10 0 reflection 0 25 refraction 0 0 refraction_index 1 0 The following picture shows the Cornell room a scene where different types of surfaces are used The following picture shows the use of fuzzy reflections in a scene Primitives This section describes the different primitives supported by YASRT Sphere The sphere is the fastest and simplest object to render with a raytracing program The syntax is a follows sphere center vector radius float Here is a description for each parameter of this structure 1 center this keyword is followed by a vector that specifies the center of the sphere This parameter is mandatory and there is no default value for it 2 radius this keyword is followed by a float that specifies the value of the radius of the sphere This parameter is mandatory and there is no default value for it The following example shows of sphere centered around the origin lt 0 0 0 gt and with a unit radius 1 sphere center lt 0 0 0 gt radius 1 The following image is an example of such a sphere Plane The syntax is a follows pla
34. on a computer It simulates the propagation of light through an environment by tracing rays of light in a scene to determine which objects they interact with It also models physical properties of lights objects and the interaction between them The simple approach of shooting rays from the lights present in a three dimensional world is simple but primitive Very few rays coming from these lights will eventually end up in the section covered by the camera A simple method used in this case is to shoot rays from the camera out into the world This technique is also known as backward raytracing Using the laws of geometric optics rays can be reflected refracted focused etc The process is recursive in nature as rays are traced not only from the camera out into the world but also out of a mirror or inside a transparent object etc Using projection formulae a pixel on the screen or final output image corresponds to one or more ray depending on the different techniques used that is sent out into the virtual world Intersection tests are then conducted for each primitive to check if the ray hits one of these primitives The algorithm then proceeds by determining the color on the surface of the primitive hit at the intersection point Depending on the primitive s surface new rays are traced for example if reflection or refraction is activated following the same algorithm Finally when a maximum number of iterations has been reached or
35. ontribution of haze in a scene see below for more details Colors YASRT makes extensive uses of colors in many of its structures A color is defined by three floating point components representing in order of appearance the red component the blue component and the green component What follows is an example of the use of a color in a YASRT script settings background 0 078 0 361 0 753 In this example the background color of the image will have a red component of 0 078 a green component of 0 361 and a blue component of 0 753 Note that for normal colors the components lie between 0 0 and 1 0 When all components are null 0 0 the color specified is black when they are all equal to 1 0 the color specified is white additionally when the components are all equal the color specified is a shade of grey Color components can be greater than 1 0 in the case of lights As a matter of fact as we will see later light can fade proportionally with distance like in the real world if the color specified in the color structure is not sufficient in this case the color of the light represents the intensity of the light the scene won t be lit properly For more details about this effect see below Another way to use colors is by declaring them as shown in the following example declare AigueMarine color 498039 1 831373 This example shows how to declare a color called AigueMarine for later use in t
36. ormats The following summarizes how to the program can be called Usage gl3ds2yst options Options w width integer width of the output image h height integer height of the output image d display string type of display points lines triangles 0 output c camera i input 1 light t triangle x texture help string integer string YASRT file to export to no extension the initial camera to use file to open with extension load lights in OpenGL experimental triangles as input default is patches load textures in OpenGL experimental this help message Example gl3ds2yst i car 3ds o cartest By default the 3D view will be displayed in wire frame mode as shown below By using the appropriate command line switch it is possible to use a shaded or point rendering mode as shown in the two following screenshots It is possible to interact with the keyboard and mouse By left clicking and moving the mouse while keep the left button pressed it is possible to look around in the 3D world of the scene The right button of the mouse activates or de activates the automatic animation of the scene rotation around the target point of the camera The keyboard interactions are summarized below Key Description gt Go to the next camera in the 3DS file lt Go to the previous camera in the 3DS file Enlarge the camera
37. pression There is no default value for this parameter output_name this keyword is followed by a string that specifies the name of the output image file The filename specified doesn t need to contain any file extension YASRT will automatically append the correct file extension to the name specified 10 jitter this keyword is followed by a string specifying if jittering should be used during the rendering of the output image Its value can be either yes or no This parameter is not mandatory and by default jittering is not activated Jittering allows YASRT to introduce pseudo random values when tracing rays This feature is useful because it helps reducing the appearance of aliasing effects see below to the human brain However jittering shouldn t be used when generating the successive frames of an animation Since pseudo random values are used when tracing rays undesired visual effects are generated noise when objects moved during animation antialiasing this keyword is followed a string specifying the type of anti aliasing to use during rendering The different values can be none no anti aliasing is used This leads to the fastest renderings at the cost of a poor quality in the results obtained This technique should be used in intermediate renderings only quick a quick anti aliasing technique is used This provides a good trade off between rendering times and rendering qualities and i
38. ration of a polygon polygon 4 vertex vertex vertex vertex lt 1 5 1 5 0 gt lt 1 5 1 5 0 gt lt 2 2 0 gt lt 2 2 0 gt Here is such a polygon Triangle The syntax is a follows triangle vertex vertex vertex vector vector vector Here is a description for each parameter of this structure 1 vertex this keyword is followed by a vector that specifies one the vertices of the triangle The vertices must be declared in the counter clockwise order Only three vertices must be declared The following example shows the declaration of a triangle triangle vertex vertex vertex lt 1 5 1 5 0 gt lt 1 5 1 5 0 gt lt 2 2 0 gt Here is such a triangle Smooth triangle patch A smooth triangle contains not only vertices but also the normal at each vertex This primitive is primarily used when exporting scenes from commercial packages The syntax is a follows patch or smooth_triangle vertex vector normal vector vertex vector normal vector vertex vector normal vector Here is a description for each parameter of this structure 1 vertex this keyword is followed by a vector that specifies one the vertices of the triangle The vertices must be declared in the counter clockwise order Only three vertices must be declared 2 normal each vertex must be directly followed by its normal The following example shows
39. rmats for easier and faster parsing and generation of large scenes 5 More auxiliary tools in the package converters plug ins for commercial 3D packages etc 6 GUI for easier manipulation and rendering Installation Notes Windows To install YASRT on Windows please do the following 1 Download YASRT from its official Web Site http www yasrt org 2 Download the Windows version for your platform Intel or Alpha 3 Unzip the archive downloaded by using WinZip for instance into a directory of your choice e g CA YASRT 4 Add the YASRT directory to your path environment variable On the desktop right click on the My Computer icon Select Properties Select the Advanced tab Windows 2000 Select Environment Variables Inthe system variables section double click on PATH Add YASRT directory e g C YASRT PocketPC To install YASRT on the pocketPC platform please do the following 1 Download YASRT from its official Web Site http www yasrt org 2 Download the pocketPC version for your platform ARM only currently 3 Unzip the archive downloaded by using WinZip for instance into a directory of your choice e g YASRT 4 The program reads a scene file called scene yst at the root directory 5 Copy any scene to the root directory and rename it to scene yst then run the program The scene will be rendered directly onto the screen and saved in the image file specified in the script
40. rt 3DS file converter and pre viewer FreeBSD Intel No Longer Supported FreeBSD can execute Linux binaries BeOS Intel Multi threading OpenGL bugs for pre BMP PPM TGA viewer no longer Native 3DS file support supported 3DS file converter Win32 Alpha Multi threading Might not be supported BMP PPM TGA TIFF JPEG amp PNG _ in the future Trix Multi threading None BMP PPM TGA AIX BMP PPM TGA Might not be supported in the future DEC UNIX BMP PPM TGA Might not be supported in the future HP UX BMP PPM TGA Might not be supported in the future Solaris BMP PPM TGA None MacOS X Multi threading None BMP PPM TGA PocketPC BMP PPM TGA Limited support Future Features The following list describes what will be implemented in future versions of YASRT e Raytracing features 1 2 A OT eS Stochastic global illumination to take into account global illumination effects path tracing Use of photon tracing for advanced effects global illumination not to be combined with path tracing and caustics More camera models orthographic and no parallax Area lights Support for procedural texturing Support for image mapping Layered fog New primitives Blobs Height fields e Technical features 1 2 de 4 Support for direct output onto the screen for more platforms Support of any number of threads Enhanced scripting language Custom binary fo
41. s slower than with no anti aliasing This technique should be used in intermediate renderings only adaptive an adaptive anti aliasing technique is used Put simple this complex technique recursively sub divides each pixel and traces new rays until a threshold is reached see below As a result far more rays are traced than in any of the previous techniques presented Calculation times are therefore tremendously increased this is why this technique should be used for final renderings The default value for this parameter is none no anti aliasing by default aa_distance this keyword is followed by an integer that specifies the threshold value used when adaptive anti aliasing is activated Low values give the best results as more rays are traced this therefore leads to longer rendering times High values give good results with faster rendering times at the cost of a poor quality in the final image This parameter is not mandatory and its default value is 64 background this keyword is followed by a color that specifies the background color of the image If a ray that is traced into the virtual world doesn t hit any primitive present the color returned is that specified by this parameter This parameter is not mandatory and its default value is black 0 0 0 haze_color YASRT can simulate haze effects This parameter is followed by a color specifying of the haze when this effect is activated This parameter is not mandatory
42. the file as Text only TexPad Windows http www textpad com vi Unix platforms Emacs Unix and Windows platforms Etc Future versions of YASRT will support binary files when image mapping is supported These binary files will be PPM files all platforms BMP files all platforms TGA files all platforms JPEG files depending on the platforms TIFF files depending on the platforms PNG files depending on the platforms On some platforms YASRT also supports the rendering of 3D Studio binary files without needing the conversion of this type of files beforehand An ASCII file needs to be created in order to tell YASRT how to render the scene The content of that file is described in the corresponding section below Output files YASRT supports binary files to output the images created The formats supported are PPM files all platforms 24 bit 16M colors uncompressed BMP files all platforms 24 bit 16M colors uncompressed TGA files all platforms 24 bit 16M colors uncompressed JPEG files platform dependant 24 bit 16M colors compressed TIFF files platform dependant 24 bit 16M colors compressed PNG files platform dependant 24 bit 16M colors compressed AAA File inclusions It is possible to include files within Y ASRT scene description files by using the include directive This feature allows artists to create libraries of o
43. tion for each parameter of this structure 1 position this keyword is followed by a vector that specifies the position of the light This parameter is mandatory and there is no default value 2 color this keyword is followed by a color that specifies the color of the light Currently YASRT supports the effect of fading of intensity the intensity of a light source decreases with the distance from the center of the light source In this case the color can be thought of as the intensity of the light Since this parameter depends on the overall scale of the scene it needs to be carefully adjusted and as a result the color of a light can have its components greater than 1 0 This parameter is mandatory and there is no default value 3 attenuation_type this keyword allows specifying which light attenuation model to use during rendering Possible values are e none no light attenuation will be used e d the attenuation will be proportional to the inverse of the distance from the light e d2 the attenuation will be proportional to the inverse of the square of the distance from the light This is the default value if the keyword is not present in the light declaration 4 shadow_type this keyword allows specifying which type of shadow to use during rendering Possible values are e sharp the shadows cast in the scene will be sharp e smooth the shadows cast in the scene will be smooth This effect is also referred to as penumbra T
44. ts of the language integers doubles strings surfaces primitives etc The declare keyword is used for that purpose The syntax of this keyword is as follows declare string data_type_name data_type_definition In the current version of YASRT data_type_name can only be color data_type_definition is therefore a color definition For example to declare a color and associate the name AigueMarine to it use the following declare AigueMarine color 498039 1 831373 To use this color later in the script the following syntax needs to be used color_name For example to use the color previously defined surface color AigueMarine It is therefore possible to define your own colors in include files and re use them in numerous scenes Future versions of YASRT will support library paths this feature will allow the raytracer to look for include files in specific directories without having to specify the full path to those files in the scenes using them 3DS File Support YASRT supports the 3DS file format natively This feature has not been implemented on all platforms yet Not all features of the file format are support either In order to activate this feature an ASCII file must be created along with the 3DS file to render This file specifies the different options that YASRT must apply to the scene when rendering it The syntax of this file is the following
45. ws disc center vector normal vector radius float Here is a description for each parameter of this structure 1 center this keyword is followed by a vector that specifies the center of the ring This parameter is mandatory and there is no default value for it 2 normal this keyword is followed by a vector that specifies the normal of the ring This parameter is mandatory and there is no default value for it 3 radius this keyword is followed by a float that specifies the value of the radius This parameter is mandatory and there is no default value for it The following example shows the declaration of a ring disc center lt 0 0 0 gt normal lt 0 0 1 gt radius 1 Here is this disc rendered Cone The syntax is a follows cone base vector cap vector base_radius float cap_radius float Here is a description for each parameter of this structure 1 base this keyword is followed by a vector that specifies the base of the cone This parameter is mandatory and there is no default value for it 2 base_radius this keyword is followed by a float that specifies the value of the radius of the cone at the base This parameter is mandatory and there is no default value for it 3 cap this keyword is followed by a vector that specifies the cap of the cone This parameter is mandatory and there is no default value for it 4 cap_radius this keyword is followe
Download Pdf Manuals
Related Search