Figure 4.

Implemented cases of subdivision. (a–d) Left column: initial tetrahedron with newly introduced vertices (red). Middle column: division into tetrahedra. Right: exploded view. (a) Only one edge is to be split. (b) A pair of opposite edges are to be split. (c) Three edges of one face are to be split. (d) Every edge is to be split. A tetrahedron is sliced off each corner of the original, leaving an octahedron which is then sliced into four more tetrahedra around one of its diagonals. (e) Example of a case that is not implemented. Two adjacent edges are to be split. There are two ways to split the face containing these edges into triangles. The tetrahedron on the other side of that face must split it in the same way. This coordination of splitting complicates the implementation.