3: Smooth Probabilistic Ambient Occlusion for Volume Rendering

Ambient occlusion [Zhukov et al. 98] is a compelling approach to improve depth and shape perception [Lindemann and Ropinski 11, Langer and Bu¨lthoff 99], to give the illusion of global illumination, and to efficiently approximate lowfrequency outdoor lighting. In principle, ambient occlusion computes the light accessibility of a point, i.e., it measures how much a point is exposed to its surrounding environment.