Global Illumination

In recent years most RenderMan implementations have added support for global illumination (GI)—that is the calculation of effects produced by light interacting with several surfaces before it reaches the camera. This allows more realistic images to be produced at the cost of additional rendering time. Because GI is potentially very slow to render, it has been incorporated into the RenderMan standard in such a way that effects can be controlled on per object basis. Only those objects which require GI need use it, while objects which can be accurately rendered with standard techniques continue to be rendered at high speed. In this chapter we will see how you can enable ray-traced shadows, reflections, caustics, and bounce light using the shading language.