Voxel Coloring Solutions
1.  C=2 (silhouettes)
Volume intersection [Baumgart 1974]
2.  C unconstrained, viewpoint constraints
Voxel coloring algorithm [Seitz & Dyer 97]
> For more info:  http://www.cs.washington.edu/homes/seitz/papers/ijcv99.pdf
3.  General Case
Space carving [Kutulakos & Seitz 98]