A certain Japanese console has a unusual need for its clipping matrix, it needs -|w| < z < +|w| rather then the usual 0 < z < w.
This means any text book clipping matrix, needs modifing for GS chip what we call FUCH-KUTARAGI-CHIP.
The best reference IMHO for clipping and perspective transforms is Jim Blin`s Trip down the Graphics Pipeline which describes the perspective system in details, and it also explains how to create your own clipping space.
