Dual Paraboloid Texture Matrix Setup (2)
P is projective transform that divides
by the z component (flattens to 2D)
T maps [ -1, 1 ] vector space range
to [ 0, 1 ] texture space range
S subtracts object-space reflection vector
from each paraboloid’s orientation, d
d is either [ 0, 0, -1 ] or [ 0, 0, 1 ]