I would love to extend processing in order to be able to render 3D stuff with oblique projections (cabinet or cavalier). After looking around the PGraphics3D#camera(), PGraphics3D#perspective() and PGraphics3D#ortho() source code I tried to set the PGraphics3D#camera matrix to an appropriate value with partial success.

Still I'm a little bit confused about the PGraphics3D#camera and PGraphics3D#projection matrices in PGraphics3D. PGraphics3D#ortho sets the latter directly. While OpenGL keeps two matrix stacks - modelView and projection, here is a third one - camera. Can anybody shed some light on the difference and relation between these matrizes?

This would help to know when to use/set which one. Thanks a lot!