Texture Mapping
- convert [i,j] to homogeneous form: [i,j,1] = p
- apply M-1: [t,r,s] = M-1p; we get a point in the square
- convert back to 2D coordinates: [t/s,r/s]
- rescale and round to get pixel coordinates: m = (int)( width*(t/s+1)/2.0); n = (int)( height*(r/s+1)/2.0);