3D visibility made visibly simple: an introduction to the visibility skeleton

Many problems in computer graphics require accurate global Visibility information, such as the view from a given point, the mutual visibility of two objects (e.g. lighting simulation), the limits of umbra and penumbra, etc. Previous approaches have used coarse approximate ions or have been complicated to implement, numerically unstable and very expensive both in storage and time. We present a new data-structure, the Visibility Skeleton, a multi-purpose tool which can answer many types of queries. It is easy to implement md has been tested with scenes of a few hundred polygons. We present the visual events which encode all visibility changes for polygonal scenes and sketch a construction rdgorithm as well as queries such as the computation of the part of a polygon visible from a vertex of the scene and the limits of umbra and penumbra between two polygons.