Fresnel
fresnel scene controls
In most physically-based rendering models surfaces will have more specular reflection when viewed at near-grazing angles. This phenomenon is typically called the fresnel effect. The fresnel factor is often approximated using Schlick’s approximation.
Fresnel shaders have two main uses - in physically-based rendering and for artistic effect.
In Physically-Based Rendering
Section titled “In Physically-Based Rendering”Many rendering models take into consideration the fresnel effect when calculating the specular reflection for surfaces. Three.js is no different and uses an approximation of the fresnel factor in a few of its materials, although, at the time of this writing, it appears that it uses a more optimized approximation.
Typically the fresnel factor is combined with other terms in BDRFs to produce the final color.
For Artistic Effect
Section titled “For Artistic Effect”Fresnel shaders are often used for artistic effect, for example to highlight interactive objects.