Abstract: Building a hierarchical vision model of an object with multiple representations requires two steps: (1) decomposing the object into parts/subparts and obtaining appropriate representations, and (2) constructing relational links between decomposed parts/subparts obtained in step 1. In this paper, we describe volume-based decomposition and surface-based decomposition of 3-D objects into parts, where the objects are designed by a B-spline based geometric modeler called Alpha-1. Multiple-representation descriptions can be derived for each of these subparts using various techniques such as polygonal approximation, concave/convex edge detection, curvature extrema, and surface normals. For example, subparts of a hammer can be described by two generalized cylinders or one generalized cylinder and one polyhedron. Several examples are presented. !10
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