Ken Silverman released source code for his PND3D voxel engine

just as a heads-up reminder for anyone taking a look at this: it's intended for non-commercial use only with a non-standard license. Parse/use at your own risk - IANAL.

Previous (pre-source code release) discussion: https://www.reddit.com/r/VoxelGameDev/comments/2988uf/ken_silverman_releases_successor_to_voxlap_pnd3d/