Browsing by Author "Nevatia, R."
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Item Open Access Perception of 3-D Surfaces from 2-D Contours(1993) Ulupinar F.; Nevatia, R.Inference of 3-D shape from 2-D contours in a single image is an important problem in machine vision. We survey classes of techniques proposed in the past and provide a critical analysis. We propose that two kinds of symmetries in figures, which are known as parallel and skew symmetries, give significant information about surface shape for a variety of objects. We derive the constraints imposed by these symmetries and show how to use them to infer 3-D shape. We discuss the zero Gaussian curvature (ZGC) surfaces in depth and show results on the recovery of surface orientation for various ZGC surfaces. © 1993 IEEEItem Open Access Recovery of 3-D objects with multiple curved surfaces from 2-D contours(Elsevier, 1994) Ulupinar, F.; Nevatia, R.Inference of 3-D shape from 2-D contours in a single image is an important problem in machine vision. Often, techniques to solve this problem examine each surface in the scene separately whereas our perception of their shapes clearly depends on the interplay between them as well. In this paper, we describe a technique that attempts to recover the shapes of all the surfaces of an object simultaneously, though it is limited to objects made of zero-Gaussian curvature surfaces. Our technique is based on an analysis of three kinds of symmetries defined in the paper and the constraints that derive from them, and from other boundaries. This technique uses some of the constraints developed in an earlier paper that was limited to examining a zero-Gaussian curvature surface cut by parallel planes. This restriction has been removed here and the constraints have been reformulated to allow integration of constraints from all the neighboring surfaces. Results on some complex examples are shown. © 1994.