Overview:

PBR specular uses a microfacet model, typically with a GGX normal distribution and Smith shadowing/masking. This talk will derive a PBR diffuse lighting model using the same microsurface, eliminating ad-hoc conversion of surface parameters between unrelated diffuse and specular models. This will shed light on microfacet models in general and some intricacies of Smith shadowing/masking and diffuse lighting models in particular. This session will see Disney's BRDF slices and how to interpret them for quick and easy BRDF comparison. Ultimately, this talk will discuss a new GGX+Smith diffuse shading model, a new and cheap approximation for Smith specular shadowing/masking, and some mathematical identities that can save 7-10 pixel shader cycles per light.