One application of these projections would be a point light source in the 4-th Dimension that would be obscured by solid 4-D toys and subsequently cast 4-D shad

One application of these projections would be a point light source in the 4-th Dimension that would be obscured by solid 4-D toys and subsequently cast 4-D shadow "voxel maps" into the 3-D cube space. Having shadows and radiosity illumination would absolutely help with the "disappearing" cubes problem during game play. But it represents a substantial calculation for real-time physics and rendering engines.