Advanced Illumination
Spring 1999
Illumination Review
Irradiance of incidence light : . where is incident radiance.
Bidirectional reflectivity :
D is distribution function of microfacets orientations
G is geometrical attenuation factor -- masking and shadowing effects of the microfacet on each other.
is the Fresnel term.
where , is angle of incidence relative to , and n is index of refraction.
In another form
where and .
where ,
and .
Also can do it as:
where Red(0) is color of material at normal incidence. Then,
Hall suggested a similar method.