Schlick's approximation

In 3D computer graphics, Schlick's approximation is a formula for approximating the bidirectional reflectance distribution function (BRDF) of metallic surfaces. It was proposed by Christophe Schlick to approximate the contributions of Fresnel terms in the specular reflection of light from conducting surfaces.

According to Schlick's model, the specular reflection coefficient R is given by

$R(\theta )=R_{0}+(1-R_{0})(1-\cos \theta )^{5}$

where $\theta$ is half the angle between the incoming and outgoing light directions, and $R_{0}$ is the reflectance at normal incidence (i.e. the value of the Fresnel term when $\theta =0$).

See also

• Phong reflection model
• Blinn-Phong shading model
• Fresnel equations