🚀 go-pugleaf

A few more things on generating shadow maps with RenderMan.  

There are basically 2 steps:

1.  Generate a depth based picture file (Z-File).  The RIB file that you want  
to render the Z information from must have a Display call along the lines of:
Display "filename" "zfile" "z"
where filename is the name of the output Z-File.  This file is not of any  
recognized format so don't bother trying to view it.  Also, shaders and light  
sources are not used so don't bother with them, either.  Your camera  
transformations should be such that your camera is at the "from" point of  
your light, and pointing at the "to" point of it.  Also, if your light is a  
distant light, then you should not use a "perspective" projection and use  
instead "orthographic".  For spotlights, you need to use "perspective".  For  
pointlights, call Pixar and get them to explain it. (It is not fun)  Another  
thing to worry about is the ScreenWindow and whether it is large enough to  
encompass all your shadow casting and casted objects.  With distant lights  
the ScreenWindow bounds get used, with spots its the fov parameter in your  
projection. Make it so. Also, make sure the output image is sized by powers  
of 2, or else you will have a very funny looking world.

2. Call RiMakeShadow("filename.zfile", "shadowfile", RI_NULL) or just stick  
the following line after the last FrameEnd in the RIB file that generates  
your z-file, and you can do both steps in one fell swoop:
MakeShadow "filename.zfile" "shadowfile"

This will create the shadowmap in the file "shadowfile".  Then you just need  
to use a lightsource shader that incorporates shadowmaps.

I think that covers most of things that can go wrong with trying to get  
shadows.

wick

Peter Wickersham
wick@stone.com