hey y'all. I found this great tutorial on the web for ray traced terrain self shadowing. its an improvement on the one from gamedev.net. It gets a huge performance gain by storing data about the heights of vertices that caused shadows. So rather than comparing against all vertex heights along the ray to test for a shadow, you compare against their height plus the height difference of it and the vertex that shadows it. They claim a shadow map that took over 10 minutes with the gamedev.net algo ran in under 10 seconds with theirs. Its a cool idea, and I've already got a few more that would further increase the best case performance.
If i ever get an ounce of free time this will be the next thing I impliment.