Some of the old-timers around here may recall the old Freon raytracer project that I worked on several years ago. The goal was to develop a software reference implementation of a hardware raytracing accelerator chip. Ironically enough, the idea looked quite similar to the Larrabee project that Intel is working on.
Freon had a couple aces up its sleeve, though, including modified photon mapping algorithms that were up to an order of magnitude faster than a reference implementation of the original algorithm by Jensen. One of them has just been independently rediscovered by Jarosz.
The other worked on a similar principle, and effectively used beam tracing for the photon tracing portion of the render, and then ran a smoothing pass through a specialized adaptive kernel to ensure an aesthetically appealing gradient of the illumination values across a surface. In essence, the gradient was controlled so that it would change at a rate that was a multiple of the rate of change of the surface normal at the point of photon collision. This system also factored in the BRDF of the surface to try to minimize bias.
So there you have it - full disclosure of everything that made Freon special.
Like I said, I'm kicking myself for not acting on the research a long time ago. As cool as it is to see very close variants of my work published, it would have been even cooler to actually have blazed the trail first. Oh well, though, that's life.
The worst part is, I worked on Freon back before I had seen the light of version control - so the only copy of the code I have is in a terrible state, doesn't compile, and doesn't even include the good implementation of the lighting algorithms I had designed. So I can't even release the source code for other people to hack on.
Maybe this will light a fire under my ass and get me working on Epoch like I should be [wink]
