What sort of projection modification must be made to project a quad with orthagonal projection (no perspective correctness)?

Don't divide by distance (Essentially the 1/d is removed)

The matrix looks like this:

cos(Oy), sin(Oy)*sin(Ox), 0, 0
0, cos(Ox), 0, 0
sin(Oy), -sin(Ox)*cos(Oy), 0, 0
0, 0, 0, 1

ISOmetric projection is a special case with Oy=45 deg. and Ox=35.26 deg.

/Niels