Image from "Coco"
While Materials control the appearance of an object, patterns control the detail by varying the parameters of the material's Bxdf across a surface. This is similar to the way texture artists use textures to control the look of a material. RenderMan ships with a set of patterns that allow texturing, color correction, bumping, and various utility shading systems.
The patterns can be divided into the following categories:
Drive patterns with texture images.
Procedurally create noise and patterns.
Manifolds tell the renderer how to apply patterns on a surface. This controls features like repetition, placement, and size.
Create or modify colors in the shading network.
You can use these nodes to calculate geometric properties and vectors.
These passthrough patterns are designed to allows users to bake arbitrary pattern networks.