Archive notice: This article was originally published on February 21, 2018. Links and embedded videos are preserved as part of the historical record.
In this rig, see the various ray behaviors when shader parameters are changed. The light rays for Reflection, Diffuse, SSS and Refcraction respectively are displayed visually. The aiStandardSurface shader from Arnold was used for this demonstration.
PBR and Shading: Theory and Application
For a deeper look at theory and application, you can look at the PBR Guides from Allegorithmic. Alongside fundamentals and representations describing the behavior of light and the BRDF (Vol.1), you will also find practical guidelines for creating PBR textures (Vol.2). There is also a good introduction to the concepts of Physically Based Shading from ACM SIGGRAPH University.
