SpecularBRDF is a shader that implemented Cook-Torrance BRDF in the Built-in Pipeline. This BRDF that uses below common form is the lighting model announced by Robert L. Cook and Kenneth E. Torrance. (BRDF, Bidirectional Reflectance Distribution Function, is a function that defines how light is reflected at an opaque surface)
f(l,v) = ( D(h) * F(v,h) * G(l,v,h) ) / ( 4 * (n⋅l)* (n⋅v) )
- l : light direction
- v : view direction
- h : half vector
- n : normal vector
This formula consists of Distribution term, Fresnel term and Geometric term. The Fresnel term was written using Schlick approximation. Distribution term was written using GGX Trowbridge-Reitz form. Geometric term was using Implicit, Neumann, Kelemen and Smith form.
implicit
kelemen
neumann
implicit
kelemen
neumann
implicit
kelemen
neumann
In case of using the form with neumann or smith geometry term, Some noises appear so it requires improvement.