I was looking at the z-clipping algorithm from my "optimal z-clipping" project and I realised the code could be made much more concise if you reduced cases 3,4,5,6 to cases 2 & 7, by relabelling the vertices in a second z-clip call. This new custom block uses 2.4x less code, and is only slightly slower than the old version. (This will be used in "3D Engine Tutorial: Part 3")
