Intro to RayGL

1. Kris Zarns Intro to RayGL

2. What it does • Creates SDL (scene description language) files for POVRay from OpenGL & Glut code • One file per frame/swap-buffer • Only requires minor modification to OpenGL code • Displays original OpenGL

3. How it works • Man in the middle approach • Intercepts key OpenGL calls • Builds SDL code to represent them • Runs OpenGL calls • State machine approach • Queries OpenGL for it's current state • Inserts this state information into SDL code

4. How to use it • Include the files raygl.h and raygldefs.h in that order • Call rayglFrameBegin at the beginning of each frame • Pass the output filename here, this increments internally, if using lab machines I recommend something in /temp so you don't overrun your home directory • Setup camera & lighting before calling frameBegin • Call rayglFrameEnd at the end of each frame • Call setRenderPov to turn SDL generation on and off

5. How to use POVRay • For rendering a single frame try $POVRay +P +w800 +h600 <file> • +P for pause when done • +w/+h set window size • +F[C,N,P,S,T] creates an output file of type (Compressed Targa-24, PNG, PPM, System(bmp), or Targa-24)‏ • -F turns file output off • +o<file> lets you set the output file name • See POVRay documentation 2.1.2 for more options

6. Things it supports directly • Camera and scene • gluPerspective,gluLookAt • Primitives • glEnd, glBegin, glVertex[3i,3f,3d] • Points, triangles, triangle strips, quad strips, polygons • Models • gluDisk, gluSphere, gluCylinder • glutSolidCone, glutSolidCube, glutSolidSphere, glutSolidTorus

7. Things it supports indirectly • Matrix Transformations • Current matrix is polled at glBegin, so all transforms are supported • Material properties • This is in place, but was not tested during the last course • Texturing • Coding is nearing completion • Lighting • Support for multiple lights of all types in any color

8. Things to avoid • Avoid making openGL calls between glBegin/End • Avoid moving lights or camera mid frame • Avoid placing lights inside of objects • Avoid using an orthogonal view • Avoid using non-planar polygons • Avoid nested calls to code containing frameBegin/frameEnd • Avoid using display lists, they're not currently supported

9. Using OpenGL texture objects • Create a list of texture names • glGenTextures • To create each texture • Bind a new texture name • glBindTexture • Load the texture • glTexImage2D • glBuild2DMipMaps • To use a texture • GlBindTexture – bind the name of the texture • Bind texture zero to stop texturing

10. Texturing in RayGL • Use texture objects as previously described • During the loading of the texture create an Image struct with the file name and texture data, see raygl.h • Pass the image struct to rayglCustomLoadedTexture • Adjust texture properties using rayglScaleTexture, rayglTranslateTexture, and rayglTextureType • Continue using textures as normal

11. Requests for new functionality • Contact me to see if there is work in progress • Be prepared to explain how you plan to use it and why • Discuss with Dr.Marsh if work on this is worthy of extra credit

12. Bugs • Compile with -wall • Check glError • If you are getting a segmentation fault, consider first if your code may be mis-allocating memory • Please read the openGL spec before asking questions • Please provide a minimal test case if you find a problem with raygl • I can be reached by email at kzarns@gmail.com