A mathematical function used in 3D graphics to describe how light scatters when it hits a surface, the Bidirectional Scattering Distribution Function (BSDF) combines the concepts of reflection and transmission of light, considering a material’s physical properties. It models the probability of light scattering in various directions upon interacting with a surface, which is crucial for accurately rendering materials photorealistic. BSDF accounts for different surface characteristics like roughness, glossiness, and translucency, enabling realistic simulations of objects under various lighting conditions.
Historical Context
The term Bidirectional Scattering Distribution Function (BSDF) was probably introduced in 1980 by Bartell, Dereniak, and Wolfe. The definition of BSDF is not well standardized, but it is most often used to name the general mathematical function which describes the way in which the light is scattered by a surface.
- Components: In practice, this phenomenon is usually split into the reflected and transmitted components, which are then treated separately as the Bidirectional Reflectance Distribution Function (BRDF) and Bidirectional Transmittance Distribution Function (BTDF) respectively.
Application in 3D Graphics
BSDF is a superset and the generalization of the BRDF and BTDF. The concept behind all BxDF functions could be described as a black box with the inputs being any two angles, one for incoming (incident) ray and the second one for the outgoing (reflected or transmitted) ray at a given point of the surface.
- Surface Characteristics: BSDF models the probability of light scattering in various directions upon interacting with a surface, accounting for different surface characteristics like roughness, glossiness, and translucency.