Shape constancy from novel views

Pizlo, Zygmunt; Stevenson, Adam K.

doi:10.3758/bf03206181

Cited by 55 publications

(47 citation statements)

References 14 publications

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“…These results clearly show that the shapes of objects can be reliably recognized when the objects contain a number of constraints and shapes may not be reliably recognized when all constraints are absent. These results are quite similar to those reported by Pizlo and Stevenson (1999), where the kinetic depth effect, rather than binocular disparity, was used as a depth cue.…”

Section: Resultssupporting

confidence: 81%

“…The results of the psychophysical experiments show that constraints such as planarity of surface contours and symmetry are critical for reliable shape constancy. These results are consistent with the results obtained in our previous psychophysical experiments on shape constancy from novel views in the presence of a kinetic depth effect (Pizlo & Stevenson, 1999). On the basis of these results, we developed a new model of binocular shape reconstruction.…”

supporting

confidence: 81%

“…The three experiments reported below were analogous to the three experiments reported by Pizlo and Stevenson (1999). The results were quite similar to those reported by Pizlo and Stevenson, where the kinetic depth effect, rather than binocular disparity, was the cue to the three-dimensionality of the stimuli.…”

supporting

confidence: 78%

“…A study reported by two of us (Pizlo & Stevenson, 1999) tested the role of constraints in shape constancy from novel views, using both structured and unstructured 3-D objects. In that study, kinetic depth effect was the primary depth cue.…”

mentioning

confidence: 99%

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Binocular shape constancy from novel views: The role of a priori constraints

Chan

Stevenson

et al. 2006

Perception & Psychophysics

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Shape constancy refers to the fact that the percept of the shape of a given object remains constant despite changes in the shape of the retinal image. The retinal image may change because of changes in the orientation of the object, relative to the observer. Shape is usually defined by angles and by ratios of distances. According to this definition, rigid motions and size scaling do not change shape. In other words, shape is invariant under similarity transformations. A perspective transformation between the 3-D scene and the 2-D retina is quite different from a similarity transformation (Pizlo, Rosenfeld, & Weiss, 1997). First of all, it is a many-to-one mapping. As a result, the information about depth is lost, and the shape on the retina may change substantially when the orientation of the object, relative to the observer, changes. It follows that shape constancy is a difficult computational problem. In the case of familiar objects, shape constancy could, theoretically, be achieved by means of a simple template-matching mechanism, in which the current view is compared with all previously seen views of the object. In order to provide an adequate test between this and other mechanisms, one should use unfamiliar objects and test shape constancy from unfamiliar (novel) views. Rock and DiVita (1987) performed the first systematic study of shape constancy from novel views, using 3-D objects. They used unstructured 3-D wire objects, which were viewed binocularly from a close viewing distance. Rock and DiVita reported a complete failure of shape constancy in the presence of a difference of only 45º between the views of an object. The authors concluded that the shapes of 3-D objects are perceived (and recognized) by memorizing a large number of 2-D images taken from many different viewing directions-the template matching mentioned in the first paragraph. In a subsequent study, Rock, Wheeler, and Tudor (1989) provided additional evidence by showing that observers cannot imagine how a novel wire object looks from a new viewing direction. The results of these two studies strongly suggest that the perceptual representation of objects does not involve 3-D properties. Biederman and Gerhardstein (1993) reported a quite different result. They used line drawings of unfamiliar 3-D geometrical objects built from geons and demonstrated almost perfect shape constancy from novel views (geons are simple 3-D objects, such as a box, cone, cylinder, or pyramid; Biederman, 1987). This result is, actually, hardly surprising because, phenomenologically, it is easy to imagine how novel or familiar objects built from geons (and many other structured objects) look from new viewing directions. In other words, Biederman and Gerhardstein's study provided strong support for the claim We tested shape constancy from novel views in the case of binocular viewing, using a variety of stimuli, including polyhedra, polygonal lines, and points in 3-D. The results of the psychophysical experiments show that constraints such as planarity of surface contour...

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Section: Resultssupporting

confidence: 81%

supporting

confidence: 81%

supporting

confidence: 78%

mentioning

confidence: 99%

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Binocular shape constancy from novel views: The role of a priori constraints

Chan

Stevenson

et al. 2006

Perception & Psychophysics

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show abstract

“…A planar 3D curve will produce a degenerate view if and only if the 3D curve projects to a straight line in the 2D image (this case is easy to detect and exclude). Preliminary experiments showed that this constraint captures some aspects of human perception of a 3D shape [6,10,24]. This observation is illustrated in Figure 13 (Figure 13a is identical to Figure 1).…”

Section: Discussionsupporting

confidence: 56%

Any Pair of 2D Curves Is Consistent with a 3D Symmetric Interpretation

Sawada¹,

Li²,

Pizlo³

2011

Symmetry

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Abstract:Symmetry has been shown to be a very effective a priori constraint in solving a 3D shape recovery problem. Symmetry is useful in 3D recovery because it is a form of redundancy. There are, however, some fundamental limits to the effectiveness of symmetry. Specifically, given two arbitrary curves in a single 2D image, one can always find a 3D mirror-symmetric interpretation of these curves under quite general assumptions. The symmetric interpretation is unique under a perspective projection and there is a one parameter family of symmetric interpretations under an orthographic projection. We formally state and prove this observation for the case of one-to-one and many-to-many point correspondences. We conclude by discussing the role of degenerate views, higher-order features in determining the point correspondences, as well as the role of the planarity constraint. When the correspondence of features is known and/or curves can be assumed to be planar, 3D symmetry becomes non-accidental in the sense that a 2D image of a 3D asymmetric shape obtained from a random viewing direction will not allow for 3D symmetric interpretations.

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Shape constancy from novel views

Cited by 55 publications

References 14 publications

Binocular shape constancy from novel views: The role of a priori constraints

Binocular shape constancy from novel views: The role of a priori constraints

Any Pair of 2D Curves Is Consistent with a 3D Symmetric Interpretation

The Whole Is Different from the Sum of Its Parts. Review of Representation and Recognition in Vision, by Edelman, S.

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