Blinn & Torrance Variation

Jim Blinn introduced another approach for computing Phong-like illumination based on the work of Ken Torrance.

His illumination function uses the following equation:

In this equation the angle of specular dispersion is computed by how far the surface's normal is from a vector bisecting the incoming light direction and the viewing direction.

q + f = a + g        q + a = g           =>    f - a = a   

  f = 2a

On your own you should consider how this approach and the previous one differ.

N : Normal to the real plan

H : Normal to the plane that would create higher reflexion towards the viewer

Advantage : the angle (N,H) will always remains between 0 and PI/2

Careful : nshiny should introduce a factor 2 with the previous expression.