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

Norman, J. Farley; Dawson, Thomas E.; Raines, Shane

doi:10.1068/p2994

Cited by 46 publications

(21 citation statements)

References 32 publications

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“…It is not clear why the same cues were not helpful in the case of flat spheroids. Present theories of structure from motion cannot explain these results, because there were no identifiable points on the surface of the spheroid that could be tracked (Norman, Dawson, & Raines, 2000). The rim slid over the surface when the spheroid was rotated in depth, so the points on the contour could not be used to establish correspondence.…”

Section: Motionmentioning

confidence: 66%

Object pose: Perceiving 3-D shape as sticks and slabs

Oomes

Dijkstra

2002

Perception & Psychophysics

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Estimating the pose (three-dimensional orientation) of objects is an important aspect of 3-D shape perception. We studied the ability of observers to match the pose of the principal axes of an object with the pose of a cross consisting of three perpendicular axes. For objects, we used a long and a flat spheroid and eight symmetric objects with aspect ratios of dimensions of approximately 4:2:1. Stimulus cues were the contour and stereo for the spheroids, and contour, stereo, and shading for the symmetric objects. In addition, the spheroids were shown with or without surface texture and with or without active motion. Results show that observers can perform the task with standard deviations of a few degrees,though biases could be as large as 30º. The results can be naturally decomposed in viewer-centered coordinates, and it turns out that the estimation of orientation in the frontoparallel plane (tilt) is more precise than estimation of orientation in depth (slant, roll). A comparison of long and flat spheroids shows that sticks lead to better performance than do slabs. This can even be the case within the same object; the pose of the stick-like aspect is seen with more precision than is the pose of the slab-like aspect. The largest biases occurred when the spheroids were displayed with the binocular contour as the only cue. We can explain these biases by assuming that subjects' settings are influenced by the orientation of the rim.

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Section: Motionmentioning

confidence: 66%

Object pose: Perceiving 3-D shape as sticks and slabs

Oomes

Dijkstra

2002

Perception & Psychophysics

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“…Similarly, studies in visual search have generally found that objects with anomalous shadows are easy to detect (Enns and Rensink 1990;Sun and Perona 1996; although see Ostrovsky et al 2001). These studies clearly indicate that shadows are processed and participate to a full 3-D reconstruction of the objects in the scene (Cavanagh and Leclerc 1989;Norman et al 2000).…”

Section: Resultsmentioning

confidence: 91%

Impossible Shadows and the Shadow Correspondence Problem

Mamassian

2004

Perception

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Shadows cast by objects contain potentially useful information about the location of these objects in the scene as well as their surface reflectance. However, before the visual system can use this information, it has to solve the shadow correspondence problem, that is to match the objects with their respective shadows. In the first experiment, it is shown that the estimate of the light source position is affected by a gradual luminance ramp added to the image. In the second experiment, it is shown that observers process impossible shadow images as if they ignored the local features of the objects. All together, the results suggest that the visual system solves the shadow correspondence problem by relying on a coarse representation of the scene.

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“…Past perceptual research on the informativeness of boundary contours, using human observers, has focused on how accurately people can recognize objects from static and deforming boundary contours (Attneave, 1954;Hayward, 1998;Norman et al, 2000), how well they can estimate objects' global orientation in space (Oomes & Dijkstra, 2002), and how they perceive their overall global shape (Cortese & Andersen, 1991;Norman, Phillips, & Ross, 2001) or motion in 3-D space (Norman & Todd, 1994;Todd, 1985). The results of the present experiments extend this previous research by showing that human observers, in addition, can reliably estimate local aspects of 3-D surface structure (i.e., ordinal depth relationships between separated surface regions) from static, disparate, and deforming boundary contours.…”

Section: Discussionmentioning

confidence: 99%