Phong Illumination Model

Phong illumination model is developed by Phong Bui Tuong. According to the model maximum specular reflection happens when b= 0 and falls when b increases.

Rapid fall is approximated by: Rapid fall

n: Specular reflection parameter

Larger values of n are for shiny surfaces and smaller values are for dull surfaces. For perfect reflector n is infinite.

Specular Intensity can be defined as:

Specular Intensity

b= angle between viewing vector and specular reflection vector R.


Calculation of reflection vector

|S| = sin a

R = N cos a + N cos a – L

R = 2N cos a – L

cos a = N. L

=> R = 2N (N.L) – L




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