Ambient occlusion is a shading and rendering technique used in 3D computer graphics, modeling, and animation to determine how exposed each point in a scene is to ambient illumination. For instance, the further one travels within a tube, the more occluded (and hence darker) the inside is compared to the exposed exterior surfaces.

Ambient occlusion can be seen as an accessibility value that is calculated for each surface point.[1] In scenes with open sky, this is done by estimating the amount of visible sky for each point, while in indoor environments, only objects within a certain radius are taken into account and the walls are assumed to be the origin of the ambient light. The result is a diffuse, non-directional shading effect that casts no clear shadows, but that darkens enclosed and sheltered areas and can affect the rendered image's overall tone. It is often used as a post-processing effect.