In 3D computer graphics, Schlick’s approximation, named after Christophe Schlick, is a formula for approximating the contribution of the Fresnel factor in the specular reflection of light from a non-conducting interface (surface) between two media.
According to Schlick’s model, the specular reflection coefficient R can be approximated by:
In microfacet models it is assumed that there is always a perfect reflection, but the normal changes according to a certain distribution, resulting in a non-perfect overall reflection. When using Schlick’s approximation, the normal in the above computation is replaced by the halfway vector. Either the viewing or light direction can be used as the second vector.
- Schlick, C. (1994). "An Inexpensive BRDF Model for Physically-based Rendering" (PDF). Computer Graphics Forum. 13 (3): 233–246. CiteSeerX 10.1.1.12.5173. doi:10.1111/1467-8659.1330233. S2CID 7825646. Archived from the original (PDF) on 2020-05-10.
- Hoffman, Naty (2013). "Background: Physics and Math of Shading" (PDF). Fourth International Conference and Exhibition on Computer Graphics and Interactive Techniques.