Physical rendering in the game (III)

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• Microfacet BRDF

In the previous article "physical-based rendering in the game (ii)", we introduced the derivation of illumination. This article will explain the physical-based BRDF.

Microfacet BRDF

The basis of most physical-based specular BRDF isMicrofacet Theory. This theory is used to describe the reflection from a general surface (not an optical smoothing. The basic assumption of microfacet theory is that manyMicro plane(Microfacet) composition, these micro-planes are too small, there is no way to see one by one; and assume that each microfacet is optical smooth.

Each microfacet reflects an Incident Direction light to a separate outbound direction, depending on the microfacet's normal direction.M. When BRDF is calculated, the Light Source DirectionLAnd line of sightVGiven. This means that in all microfacet on the surface, onlyLReflectedVWhich contributes to BRDF. In, we can see theseEffective microfacetSurface normal directionMExactly inLAndVIn the middle, that isH.

 

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