I started to develop of a CUDA-based "Light Server" for renderman.
And for best understanding and debuging alghoritms I implemented a special Maya locator.
It generates random directions(vectors) in a hemisphere domain.
Color of the vectors calculate by light integrator of area light samples.

Several month ago I wrote simple MAYA plug-in for converting data from MAYA PaintFX to renderman poinclouds. Generated pointclouds lightweight in contrast to ordinary baked ptc. In result point based occlusion don't physically corrected but plausible for long shots and very fast in rendering.

Autodesk MAYA Bug Tracking page

http://spreadsheets.google.com/ccc?key=pdI8BlSwGdr0btApDuZEcKQ&inv=py&pli=1#gid=0