Global illumination (shortened as
GI) or
indirect illumination is a general name for a group of
algorithms used in
3D computer graphics that are meant to add more realistic lighting to 3D scenes. Such algorithms take into account not only the light which comes directly from a light source (
direct illumination), but also subsequent cases in which light rays from the same source are reflected by other surfaces in the scene, whether reflective or not (
indirect illumination).