A mathematical function used in 3D graphics to describe how light scatters when it hits a surface. It combines the concepts of reflection and transmission of light, considering a material’s physical properties. BSDF models the probability of light scattering in various directions upon interacting with a surface, which is crucial for accurately rendering materials photorealistic. It accounts for different surface characteristics like roughness, glossiness, and translucency, enabling realistic simulations of objects appearing under various lighting conditions.