Just thought I would share another voxel engine (closed sourced, not publicly available ). I linked to the comment section as there is some interesting information and discussion, but be sure to check out the video as well.

http://www.reddit.com/r/gamedev/comments/lks76/voxel_terrain_beyond_blocks/

If I understand him correctly, he is effectively drawing 1.6 billion voxels (every frame?) at 100fps on the gpu. He also mentions an interesting method for LOD.

That's pretty cool, though strongly inspired by the NVidia demo. Actually it encouraged me to try out the NVidia demo which I discovered you can get from here. If you can ignore the awkward controls it's pretty intetresting.

The NVidia demo doesn't seem to have very good LOD, but riles2 says the transitions are harder to see in his version. From his description he has the high LOD and the low LOD overlapping by one block, which of course is also possible in PolyVox. I do believe that would fix the LOD transitions almost completly (haven't tested it myself) though it would probably push up the batch count. I'm not how how much that matters when the system is driven by the GPU, though.

Hopefully he'll release a demo in the future.