Gladius GPRT in Real Time Land
Gladius, a Ray Tracer I coded up to be so general purpose that it handles both Realtime & Non-Realtime (i.e. Realistic) Ray Tracing. In the end, it failed due to the big amount of maintaining it needed.
You can find lots of information on gladius and lots of links on further readings in its blog.
No sourcecode inside, just the binary: http://phresnel.org/d/gladius.demos.1.win32.rar