Interpolation in structure from motion

Saidpour, Asad; Braunstein, Myron L.; Hoffman, Donald D.

doi:10.3758/bf03212235

Cited by 31 publications

(8 citation statements)

References 38 publications

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“…The present results suggest that the internal noise in the visual system is reduced by integrating over space. This is in agreement with experiments on surface interpolation (Husain, Treue, & Anderson, 1989;Saidpour, Braunstein, & Hoffman, 1992), which indicate that the visual system can integrate motion information spatially for SfM. Thresholds expressed in the maximum angular difference between the displacement vectors with the mean direction (after removal of global rotation and magnification) are largely independent of the wavelength.…”

Section: Discussionsupporting

confidence: 76%

Monocular discrimination of rigidly and nonrigidly moving objects

Hogervorst

Kappers

Koenderink

1997

Perception & Psychophysics

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Wemeasured thresholds for the monocular discrimination of rigidly and nonrigidly moving objects defined by motion parallax. The retinal projections of rigidlymoving objects are subject to certain constraints. By applying smooth 2-Dtransformations to the projections of rigidly moving objects, we created stimuli in which these constraints were affected. Thresholds for (generic) nonrigidtransformations that in theory can be detected from rigid ones by processing pairs of views depended not only on the extent to which the rigidity constraints were affected, but also on the structure and the movement of the simulated object. Nonrigid transformations under which every three successive views had a rigid interpretation were not discriminable from rigid transformations, except in cases where the distortions were very large. Under the rigidity assumption, this would mean that a large class of nonrigidly moving objects is erroneously perceived as rigidly moving.When moving around in the world, we have the impression that the world is stable, rigid, and three-dimensional. This is perhaps remarkable considering the fact that the retinal images change over time. Many experiments show that the visual system is capable of extracting useful information about 3-D structure from these retinal changes. The process involved is usually called structure-frommotion (SfM).Unless assumptions are made about how the world changes over time, motion parallax does not provide us with information about depth. Without such assumptions there is a large class ofpossible interpretations ofthe underlying scene, including an interpretation formed by a set ofmarkers moving in the frontal plane. An assumption frequently used in the literature is the rigidity assumption.

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Section: Discussionsupporting

confidence: 76%

Monocular discrimination of rigidly and nonrigidly moving objects

Hogervorst

Kappers

Koenderink

1997

Perception & Psychophysics

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“…Our previous study of surface interpolation (Saidpour et al, 1992) used stimuli similar to those of the present study, with one difference: the dots in the previous study lay on the surface of a cylinder rather than on a dihedral angle. In that study, we found that subjects placed the probe dot significantly outside a true cylindrical interpolation.…”

Section: Discussionmentioning

confidence: 99%

“…In a previous study of surface interpolation in SFM, Saidpour, Braunstein, and Hoffman (1992) used stimuli similar to Grimson's half cylinders. The displays were orthographic projections of dots on the surface of half cylinders rotating back and forth ±19°about a vertical axis through the center of the cylinder.…”

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confidence: 99%

Interpolation across surface discontinuities in structure from motion Asad Satdpour

Saidpour

Braunstein

Hoffman

1994

Perception & Psychophysics

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Interpolation across orientation discontinuities in simulated three-dimensional (3-D) surfaces was studied in three experiments with the use of structure-from-motion (SFM) displays. The displays depicted dots on two slanted planes with a region devoid of dots (a gap) between them. If extended through the gap at constant slope, the planes would meet at a dihedral edge. Subjects were required to place an SFM probe dot, located within the gap, on the perceived surface. Probe dot placements indicated that subjects perceived a smooth surface connecting the planes rather than a surface with a discontinuity. Probe dot placements varied with slope of the planes, density of the dots, and gap size, but not with orientation (horizontal or vertical) of the dihedral edge or of the axis of rotation. Smoothing was consistent with models of 2-D interpolation proposed by Ullman (1976) and Kellman and Shipley (1991) and with a model of 3-D interpolation proposed by Grimson (1981). Wallach and O'Connell (1953) demonstrated that if subjects are shown the two-dimensional (2-D) shadow cast by a clear glass sphere that has small opaque dots on its surface and rotates about a vertical axis, then subjects perceive a spherical surface. A similar perception is commonly reported for computer-generated displays in which dots move about on a computer screen in a manner consistent with their being projections of dots on a rotating sphere (see, e.g., Braunstein, 1966;Braunstein & Andersen, 1984). Apparently human vision is adept at inferring 3-D structure from the 2-D motions of projected features. This process of inferring 3-D structure from 2-D motions, referred to as structure from motion (SFM) after Ullman (1979), has been studied extensively since the advent of computer-generated displays. (For reviews, see Braunstein, 1978Braunstein, , 1983Braunstein, , 1988 In many displays of SFM in which dots alone are projected on the computer screen, observers report seeing more than just a 3-D structure for the dots. They report, in addition, that they perceive a continuous surface in 3-D passing through, or near, the dots. Such perceptions of "subjective surfaces" on the basis of sparse collections of dots are not limited to SFM displays. Subjective surfaces have also been reported,

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“…The companion paper (Hildreth, Ando, Andersen & Treue, 1995) provides a discussion of possible implementations of such a process (see also Ando, 1992;Hildreth, Ando, Andersen & Treue, 1991). Recently, Saidpour, Braunstein and Hoffman (1992) also described interpolation in the perception of SFM.…”

Section: Introductionmentioning

confidence: 99%

Structure-from-motion: Perceptual evidence for surface interpolation

et al. 1995

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Dynamic random-dot displays representing a rotating cylinder were used to investigate surface interpolation in the perception of structure-from-motion (SFM) in humans. Surface interpolation refers to a process in which a complete surface in depth is reconstructed from the object depth values extracted at the stimulus features. Surface interpolation will assign depth values even in parts of the object that contain no features. Such a "fill-in" process should make the detection of featureless stimulus areas ("holes") difficult. Indeed, we demonstrate that such holes in our rotating cylinder can be as wide as one-quarter of the stimulus before subjects can reliably detect their presence. Subjects were presented with a variation on the rotating cylinder in which all dots were oscillating either in synchrony or asynchronously. Subjects perceive a rigidly rotating cylinder even when such a percept is not in agreement with the physical stimulus. To reconcile this discrepancy between actual and perceived stimulus we propose that individual points contribute to a surface based object representation and that in this process the visual system looses access to the identity of the individual features that make up the surface. Finally we are able to explain a variety of previously documented perceptual peculiarities in the perception of structure-from-motion by arguing that the perceptual interpretation of the object's boundaries influences the surface interpolation process. These findings offer strong perceptual evidence for a process of surface interpolation and are also physiologically plausible given results from recordings in awake behaving monkey cortical areas V1 and MT. The companion paper demonstrates how such a surface interpolation process can be incorporated into a structure-from-motion algorithm and how object boundaries can influence the perception of structure-from-motion as has been demonstrated before and in this paper.

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Interpolation in structure from motion

Cited by 31 publications

References 38 publications

Monocular discrimination of rigidly and nonrigidly moving objects

Monocular discrimination of rigidly and nonrigidly moving objects

Interpolation across surface discontinuities in structure from motion Asad Satdpour

Structure-from-motion: Perceptual evidence for surface interpolation

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