ENTITY-BASED ASPECT GRAPHS - MAKING VIEWER CENTERED REPRESENTATIONS MORE EFFICIENT

The aspect graph, a graphical representation of an object's characteri stic views has been widely developed by several researchers. However, researchers have stated that aspect graphs are limited due to their hi gh complexity and computational cost. A simple non-convex object, such as a step, has 71 distinct characteristic views (nodes in the aspect graph); more complicated objects could have thousands of characteristi c views (nodes). Many characteristic views of an aspect graph are not necessary for many applications. In this paper, a new entity-based asp ect graph, EAG, is proposed based on the observation that, for most ap plications, the visibility of only some of the entities on the object is important. The objects of interest are polyhedral solids. We presen t algorithms for constructing new entity-based aspect graphs based on the faces, edges and vertices of the object, and for combining and con tracting previously constructed EAGs in a database to generate EAGs fo r new objects. The computation time for construction is reduced, yet s ufficient information is provided to the application. (C) 1998 Elsevie r Science B.V. All rights reserved.