global illumination

light transport

Global illumination can provide great visual benefits, but we’re not always willing to pay the price. In production we often have constraints of time and resources that can make traditional global illumination approaches unrealistic. “Reflection Occlusion” and “Ambient Environments” have provided us with several reasonably efficient and flexible methods for achieving a similar look but with a minimum of expense. This chapter will cover how Industrial Light and Magic (ILM) uses Reflection Occlusion and Ambient Environment techniques to integrate aspects of global illumination into our standard RenderMan pipeline. Both techniques use a ray-traced occlusion pass that is independent of the final lighting. The information they contain is passed on to our RenderMan shaders where they are used in the final lighting calculations. This allows lighting and materials too be altered and re-rendered without having to recalculate the occlusion passes themselves. We will show that when used together these two techniques have given us an integrated solution for realistically lighting scenes. They allow us to decrease setup time, lighting complexity, and computational expense while at the same time increasing the overall visual impact of our images.

Production-Ready Global Illumination