The aspect graph, a graphical representation of an object'scharacteristic views has been widely developed by severalresearchers. However, researchers have stated that aspect graphs arelimited due to their high complexity and computational cost. A simplenon-convex object, such as a step, has 7l distinct characteristicviews (nodes in the aspect graph); more complicated objects couldhave thousands of characteristic views (nodes). Many characteristicviews of an aspect graph are not necessary for many applications. Inthis paper, a new entity--based aspect graph, EAG, is proposed basedon the observation that, for most applications, the visibility ofonly some of the entities on the object is important. The objects ofinterest are polyhedral solids. We present algorithms forconstructing new entity-based aspect graphs based on the faces, edgesand vertices of the object, and for combining and contractingpreviously constructed EAGs in a database to generate EAGs for newobjects. The computation time for construction is reduced, yetsufficient information is provided to the application.
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