I don't think you meant to say "same results", Matt. Interpolating the vertex positions and computing a light direction in the pixel shader will not give the same result as computing a light direction at each vertex and interpolating these vectors over the triangle. The former is correct while the latter is incorrect, in the sense of the resulting vector accurately pointing at the light source. You might say "similar results" in that interpolating the direction vectors isn't grossly inaccurate (for some definition of grossly).
You will get the same results by interpolating the positing and then computing the light direction in the pixel shader...this is because vertex positions can be linearly interpolated. So you don't have anything to worry about.
Christer EricsonMember Since 05 Sep 2004
Offline Last Active Dec 30 2011 05:08 PM