David Skyfall, a reader of this blog (Zelcious on Twitter), has sent me a link to a downright amazing video of something he's working on: a real-time procedural volume path tracer running on a GTX 480 in 720p (100-200 million samples/second):
He also sent me this direct feed image, which rendered for about 30 seconds:
The geometric detail in the picture is just nuts. In a polygonal version, this model would probably be several billions of polygons. The voxel representation allows efficient rendering with GI in real-time. You can see blue-ish lighting from the sky (on the left part) and proper occlusion of environment light on the hollow inside.
This is the second real-time volume path tracer that I know of. The other one, Exposure Render (http://raytracey.blogspot.com/2011/10/update-2-on-exposure-render.html), is a very impressive CUDA based real-time photorealistic volume renderer for volumes scanned with CT and MRI.