Class 1: PRMan, shading, RSL - overview
Introductory material from the beginner RMan class.
Pixar's summary of the REYES algorithm:
Programmable shading - Rob Cook

Rob's idea was that complex appearances can be synthesized from simpler shading blocks, in a 'shade tree' fashion. Eg. a 'plastic' shader contains contributions from ambient, diffuse and specular components.

Here's the shade tree for PRMan's 'plastic' shader:

At first, such shade trees were implemented purely by hand-coding. Interestingly, this method is the focus of this course since hand-coding is more powerful and flexible compared to existing connect-the-blocks approaches (see below).

What if you want to visually synthesize shade trees [no programming!]?

Shading notes - beginner RMan course, class #2.
Another introduction to RenderMan [from my portion of a proposed course for SIGGRAPH 2006].