Part decomposition and shape description
H. Rom · University of Southern California Digital Library · 2017
We address the problem of obtaining natural descriptions of shapes. Shape description is a major problem in machine perception, and is the basis for recognition. The requirements from good descriptions, which facilitate recognition, lead to segmented descriptions, given in terms of parts and their arrangement. We address two and three dimensional shapes. For both we suggest methods for decomposing the shapes into their parts and for deriving natural descriptions of these parts. Given a planar shape, we suggest a method for producing a segmented axial description of the shape, together with a hierarchical decomposition of the shape into its parts. The novelty of our approach lies in the combination of several competing approaches and tools, into a unified scheme and an efficient implementation producing natural descriptions. We use Smooth Local Symmetries for the axial description of parts, suggested by curvature sign changes. We use parallel symmetries to provide information on global relationships within the shape. This information is used for parsing the shape into a hierarchy of parts. Our method is computationally efficient, robust, stable, and results show that it provides intuitive shape descriptions. We present one of the first attempts to address the description of 3-D compound objects, where the parts are connected smoothly. The input we consider is either complete 3-D or range data from a single view. We suggest a volumetric graph representation of the object, where the nodes represent individual parts and the edges represent connectivity information. We suggest the use of properties of the parabolic curves for performing the part decomposition. We currently consider objects with parts with tubular structure. The graph presents a structural description of the shape in terms of parts. We are also interested in the internal description of the parts. We study two well defined classes of shapes, Straight Homogeneous Generalized Cylinders, and Planar Right Constant Generalized Cylinders. We suggest the use of properties of the parabolic curves for recovering natural descriptions of these classes in terms of their cross sections and axes. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089-0182.)