Spatiotemporal Contour Grouping Using Abstract Part Models

Part Models Pablo Sala, Diego Macrini, and Sven Dickinson 1 University of Toronto, 2 Queen’s University Abstract. In recent work [1], we introduced a framework for modelIn recent work [1], we introduced a framework for modelbased perceptual grouping and shape abstraction using a vocabulary of simple part shapes. Given a user-defined vocabulary of simple abstract parts, the framework grouped image contours whose abstract shape was consistent with one of the part models. While the results showed promise, the representational gap between the actual image contours that make up an exemplar shape and the contours that make up an abstract part model is significant, and an abstraction of a group of image contours may be consistent with more than one part model; therefore, while recall of ground-truth parts was good, precision was poor. In this paper, we address the precision problem by moving the camera and exploiting spatiotemporal constraints in the grouping process. We introduce a novel probabilistic, graph-theoretic formulation of the problem, in which the spatiotemporal consistency of a perceptual group under camera motion is learned from a set of training sequences. In a set of comprehensive experiments, we demonstrate (not surprisingly) how a spatiotemporal framework for part-based perceptual grouping significantly outperforms a static image version.