Ambient occlusion is a fast and computationally inexpensive way to simulate indirect illumination. It works by firing sample rays into a predefined hemispherical region above a given point on an object's surface in order to determine the extent to which the point is blocked - or occluded - by other geometry. Once the amount of occlusion has been determined, a bright and a dark color are returned for points that are unoccluded and occluded respectively. Where the object is partially occluded the bright and dark colors are mixed in accordance with the amount of occlusion.Topics in this section