During the Illumination process:

For each vertex of triangle
  (in world or lighting space)
    Compute ray from the
      projective texture's origin
      to point
    Compute homogeneous
      texture coordinate,[ti, tj, t]
        (use equation from last slide)
During scan conversion
  (in projected screen space)
    Interpolate all three texture
    coordinates in 3-space
      (premultiply by w of vertex)
    Do normalization at
    each rendered pixel
        i = t i / t,      j = t j / t
    Access projected texture