Question

Differentiate between Phong and Modified Phong model.

Answer 1

First difference is that the modified Phong model uses the half-vector which can mathematically be defined as the sum of the viewing direction and incoming light direction divided by the magnitude of the two. which is then applied to the surface normal and dot product between the two is calculated whereas in the normal model the dot product is calculated between the viewing direction and the perfect specular reflection direction.Calculating the halfway vector is easier.

Second,difference between these two is that the angle formed between the halfway vector and the surface normal is comparatively shorter than the angle formed between view vector and reflection vector.