A small update on my global illumination renderer, I've ported the radiance transfer to the GPU. It was fairly straight forward as my CPU tree structure was already set up for easy GPU traversal, basically just a matter of converting array offsets into texture coordinates and packing into an indices texture.

The hardest part is of course wrangling OpenGL to do what you want and give you a proper error message. This site is easily the best starting point I found for GPGPU stuff:

http://www.mathematik.uni-dortmund.de/~goeddeke/gpgpu/tutorial.html

So here's an image, there are 7850 surfels, it runs about 20ms on my old school NVidia 7600, so it's still at least an order of magnitude or two slower than you would need for typical game scenes. But besides that it's fun to pull area lights around in real time.

Not as much colour bleeding as you might expect, there is some but it is subtle.