The first question that needs to be answered is “What exactly is RenderMan?” Contrary to the common missuse of the term within the animation and effects industry, RenderMan is not the renderer developed and used by Pixar to produce their animated movies. In fact RenderMan is not a piece of software at all. RenderMan is a rendering API. What this means in practice is that RenderMan defines how animation and modeling software, like SoftImage or Maya, should talk to rendering software, as in Figure 1.1. The rendering software receives instructions from the modeler that describe the scene and from these commands it generates images. This separation of modeling from rendering benefits developers of modeling software, developers of renderers, and end users. The API was developed by Pixar in the late 1980s at a time when they were developing custom rendering hardware. They were concerned that as wide a range of users as possible should