Recently, Pixar made the latest version of RenderMan available for free for noncommercial use. RenderMan 19 added RIS rendering, an optimized mode for rendering global illumination.
RIS was build specifically for ray tracing scenes that have heavy geometry, such as hair, volumes, and irradiance, and efficiently rendering it in a single pass. This is in addition to RenderMan’s REYES mode, which was the only mode in previous versions.
Here, Pixar posts a look into using RenderMan’s RIS rendering mode, on a project which will walk though creating a realistic rendering of a classic automobile.