Measurement and modeling of microfacet distributions under deformation

We endeavor to model dynamic microfacet distributions of rough surfaces such as skin to simulate the changes in surface BRDF under stretching and compression. We begin by measuring microfacet distributions at 5-micron scale of several surface patches under controlled deformation. Generally speaking, rough surfaces become flatter and thus shinier as they are pulled tighter, and become rougher under compression. From this data, we build a model of how surface reflectance changes as the material deforms. We then simulate dynamic surface reflectance by modifying the anisotropic roughness parameters of a microfacet distribution model in accordance with animated surface deformations. Furthermore, we directly render such dynamic appearance by driving dynamic micro geometries to demonstrate how they influence the meso-scale surface reflectance.