Global Illumination

Concept • Raytracing can render certain important effects • For example… • transparency • refraction (bending) of light through transparent surfaces • reflection of light from a shiny surface to other surfaces • (See the Raytracing tutorial in this set) • It can not render • reflection of light from a diffuse (i.e., not shiny) surface • for example, from… • a concrete wall • a colored piece of cardboard • To do this you need an approach called radiosity • When radiosity and raytracing are combined • it is called global illumination • That is, an illumination algorithm • that combines all the types of light in the scene • The most common algorithm for global illumination • tracks light photons as they move through space\ • It can require huge numbers of photons • to get an accurate rendering • Therefore… • Global illumination can be quite slow and calculation intensive • There are various trick techniques that simulate it • For example, the so-called dirt map