It is used to approximate self-shadowing and adds realism to lighting by mimicking the effects of indirect light sources such as sky, ground, walls, and so on. It measures the extent to which a location on the surface is obscured from surrounding light sources. TOM McREYNOLDS, DAVID BLYTHE, in Advanced Graphics Programming Using OpenGL, 2005 15.14.3 Ambient OcclusionĪmbient occlusion is a scalar value recorded at every surface point indicating the average amount of self-occlusion occurring at the point on the surface.