Abstract: This survey deals with obscurances and ambient occlusion. These are relatively cheap techniques that simulate diffuse indirect illumination in a way that looks realistic, though they are not global illumination techniques. The concept of obscurances first appeared in the late 1990s in the context of videogames and a few years later the idea was simplified and used in production rendering of movies under the name of ambient occlusion. In recent years many articles with ideas to improve or accelerate these techniques have appeared, while ambient occlusion has been included in commercial renderers and popularized in videogames and the movie industry.

This survey reviews the birth and evolution of obscurances and ambient occlusion techniques in recent years.