You might want to look into using the GPU for the raycasting. You can accelerate that sort of thing by a massive amount using the GPU for your heavy lifting. On something like this it's not like raycasting on the GPU is going to be cutting into other GPU accelerated stuff.
I just did a quick search and saw this: http://www.daimi.au.dk/~trier/?page_id=98
Not entirely the same thing, but probably helpful. Some googling provides these links:
No idea how useful these would be, but there might be some techniques in those that help.
bobbiasMember Since 06 Aug 2002
Offline Last Active Jun 22 2012 05:39 AM