It's just normal old raycasting through a voxel grid a la Amanatides and Woo:
http://www.cse.yorku.ca/~amana/research/grid.pdf https://github.com/cgyurgyik/fast-voxel-traversal-algorithm/...Casting the rays from the camera will be nice and coherent, plus you probably get much better and easier shadowing using ray casts compared to shadow maps.
