The Viewpoint Consistency Constraint (Classic Reprint)

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Excerpt from The Viewpoint Consistency ConstraintIn this paper we will examine one of the central constraints provided by prior three dimensional knowledge, which allows us to relate the three-dimensional structure of an object and its components to the two-dimensional spatial structure of its projection in an image. As in other areas of artificial intelligence, the effective application of such a strong constraint leads not only to increased robustness but also to a large reduction in the search space that must be explored during the process of interpretation. The particular constraint that we will be examining can be stated as follows: The viewpoint consistency constraint: The locations of all projected model features in an image must be consistent with projection from a single viewpoint.The ease of stating this constraint is deceptive. The mathematical and practical problems of implementing it have been such that few model-based vision systems have made full use of the constraint. Some systems have ignored it altogether while others have used loose approximations that discard much of the inherent information content. However, the importance of this constraint for achieving robust recognition can hardly be overstated, and we will argue that it plays a central role in most instances of human visual recogntion. Since the appearance of a three-dimensional object can change completely as it is projected from different viewpoints, any attempt to recognize an object without application of the viewpoint consistency constraint will end up ignoring most of the constraining aspects of an object's spatial structure. Low-level vision has proved unsuccessful at generating stable, unambiguous features that in themselves provide reliable discrimination between object classes. However, low-level vision provides not only the identity of features, such as edges, but also accurate information regarding their location in the image. It is this large quantity of accurate spatial information that can be exploited through application of the viewpoint consistency constraint.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.