Variation of Intensity - Modeling and Rendering
According to the phong model the variation of Intensity (I) along with α (since I α cosnα) is:
i) for shiny surface (n > 1)
ii) Dull surface (n ~= 1)
By the Phong specular reflection as:
I or Ispec. = Is Ks cosnα
Here, Is → intensity of source
I OR Ispec → intensity of specular reflected light
Ks → Specular reflection coefficient effecting intensity in the case while all ambient or diffuse or specular reflection arises as:
I = Ia Ka + Id Kd cos θ + Is Ks cosnα
Now, cosn α= (R¯ V¯)n (? Qcosnα = R¯ V¯).
Here,
R¯ → Unit vector in specular reflection direction
V¯ → Unit vector pointing the viewer
It is | V¯ | = 1 ; | R¯ | = 1.
R¯ V¯= | R¯ | | V¯ | cos α = 1.1. cos α = cos α.
( ⇒ cos α = R¯ V¯)