The concept of Physically Based Shading has been around for about a decade now, but beyond the initial concept, many advances have been made over the years to improve aspects like energy preservation or add effects such as sheen.

Recently, many renderers' Standard Material shaders have converged on similar BSDFs and layering schemes, so now is a good time to look at what this new standard looks like and how it differs from the "original" PBR scheme.

We'll start with the physical origins of the effects that we're trying to model and cover how these are abstracted and modeled in computer graphics.

Based on this, we'll go over the components that make up these modern PBR shaders, with a specific focus on the recent advances in handling of energy conservation and preservation and their interaction with Fresnel effects.

Finally, a look at how this is implemented specifically in Blender's production path tracer Cycles and some interesting aspects of how such models are translated into practice.