Illumination is enlightening—literally. Illumination is effectively lighting, and without it all of our images would be rather lacking in, well, luminosity. Illumination can take on many different forms in computer graphics and illustration. You have likely heard the term “global illumination,” which is a more realistic form of computer light rendering. There is also direct illumination and indirect illumination. Direct illumination is the original form of computer graphics lighting, and indirect illumination is a form of global illumination.