Parsing silhouettes: The short-cut rule

Singh, Manish; Seyranian, Gregory D.; Hoffman, Donald D.

doi:10.3758/bf03205536

Cited by 158 publications

(165 citation statements)

References 57 publications

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“…Specifically, although the minima rule provides a number of candidate part boundaries (namely, the negative minima of curvature), it does not indicate how these boundaries should be paired to form part cuts that segment the shape. Furthermore, even in shapes containing exactly two negative minima, simply connecting these two minima does not necessarily yield intuitive part segmentations (see e.g., Singh, Seyranian & Hoffman, 1999;Singh & Hoffman, 2001 for examples). The basic limitation of the minima rule stems from the fact that localizing negative minima of curvature involves only the local geometry of the bounding contour of the shape, but not the nonlocal geometry its interior region (see Section 4 for more on this important distinction).…”

Section: Part-based Representations Of Shapementioning

confidence: 99%

Visual Representation of Contour and Shape

Singh

2014

Oxford Handbooks Online

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Contours provide an essential source of information about shape and, along contours, points with the greatest magnitude of curvature tend to be most informative. This concentration of information is closely tied to internal generative models of contours employed by the visual system. In going from open to closed contours, the sign of curvature becomes perceptually significant, with negative-curvature (concave) sections of a contour being more informative, and playing an important role in part segmentation. The visual system represents complex shapes by segmenting them into simpler parts ("simpler" because they have less negative curvature). Points of negative minima of curvature provide an important cue for part segmentation; however being entirely local and contour-based features, they cannot fully predict part segmentation. The visual system employs not only a contour-based representation of shape, but also a region-based one, making explicit properties such as axis curvature, local width of the shape, and locally-parallel and locally-symmetric structure. A region-based representation of shape based on Bayesian estimation of the shape skeleton provides a successful account of part segmentation. Moreover, psychophysical results from a variety of domains provide evidence for the representation of region-based geometry by human vision, based on the shape skeleton. Even at the level of so-called "illusory contours," nonlocal region-based geometry exerts a strong influence. We conclude that, as far as the visual representation of shape is concerned, contour geometry cannot ultimately be studied in isolation, but must be considered conjointly with region-based geometry.

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Section: Part-based Representations Of Shapementioning

confidence: 99%

Visual Representation of Contour and Shape

Singh

2014

Oxford Handbooks Online

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“…In this paper, we will study the simple case of two-part shapes that can be segmented by joining two negative minima of curvature on the contour of the shape. In addition to negative minima, recent work has also pointed to the role of more global, regionbased, geometric factors in determining perceived shape in general (Burbeck & Pizer, 1995;Kimia, Tannenbaum, & Zucker, 1995) and part structure in particular (Siddiqi & Kimia, 1995;Siddiqi, Tresness, & Kimia, 1996;Singh & Hoffman, 2001;Singh, Seyranian, & Hoffman, 1999). The method developed in this paper will allow us to study more complex cases as well.…”

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Early computation of part structure: Evidence from visual search

Singh

2002

Perception & Psychophysics

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The visual system represents object shapes in terms of intermediate-level parts. The minima rule proposes that the visual system uses negative minima of curvature to define boundaries between parts. We used visual search to test whether part structures consistent with the minima rule are computed preattentively-or at least, rapidly and early in visual processing. The results of Experiments 1 and 2 showed that whereas the search for a non-minima-segmentedshape is fast and efficient among minimasegmented shapes, the reverse search is slow and inefficient. This asymmetry is expected if parsing at negative minima occurs obligatorily. The results of Experiments 3 and 4 showed that although both minima-and non-minima-segmentedshapes pop out among unsegmented shapes, the search for minimasegmented shapes is significantly slower. Together, these results demonstrate that the visual system segments shapes into parts, using negative minima of curvature, and that it does so rapidly in early stages of visual processing.

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“…In contrast, views that did not contain any such significant features were invariably difficult to identify. Such convex and concave regions were shown by Koenderink and van Doorn in 1976 to correspond to elliptic (ie`bump-like') and hyperbolic (ie`saddle-like') regions on the surface of a 3-D object, respectively (also see Hoffman and Richards 1984;Koenderink 1984aKoenderink , 1984bRichards et al 1987;Singh et al 1999). Koenderink and van Doorn's finding is important, because all smoothly curved solid objects can be described or represented in terms of these qualitatively distinct types of surface regions, along with the parabolic (ie`cylinderlike') surface regions that separate them.…”

Section: Discussionmentioning

confidence: 99%

The Perception and Recognition of Natural Object Shape from Deforming and Static Shadows

2000

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In this study of the informativeness of shadows for the perception of object shape, observers viewed shadows cast by a set of natural solid objects and were required to discriminate between them. In some conditions the objects underwent rotation in depth while in other conditions they remained stationary, thus producing both deforming and static shadows. The orientation of the light source casting the shadows was also varied, leading to further alterations in the shape of the shadows. When deformations in the shadow boundary were present, the observers were able to reliably recognize and discriminate between the objects, invariant over the shadow distortions produced by movements of the light source. The recognition performance for the static shadows depended critically upon the content of the specific views that were shown. These results support the idea that there are invariant features of shadow boundaries that permit the recognition of shape (cf Koenderink, 1984 Perception13 321–330).

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Parsing silhouettes: The short-cut rule

Cited by 158 publications

References 57 publications

Visual Representation of Contour and Shape

Visual Representation of Contour and Shape

Early computation of part structure: Evidence from visual search

The Perception and Recognition of Natural Object Shape from Deforming and Static Shadows

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