Perception of surface curvature and direction of illumination from patterns of shading.

Todd, James T.; Mingolla, Ennio

doi:10.1037/0096-1523.9.4.583

Cited by 147 publications

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“…Several notable psychophysical experiments on estimating local shape from shading are reported by Todd and Mingolla (Mingolla & Todd, 1986;Todd & Mingolla 1983;Todd & Reichel, 1991). In these experiments, subjects had to judge the surface orientation of patches on ellipsoids with different eccentricity in the viewing direction.…”

Section: Discussionmentioning

confidence: 99%

“…Most computational theories on shape from shading calculate the surface shape locally (Horn, 1975(Horn, , 1977Pentland, 1984Pentland, , 1989Woodham, 1980). It is not clear whether human observers are able to judge the local shape of an object on the basis of shading.Several psychophysical experiments report observers' ability to estimate local surface structure from shading (Biilthoff & Mallot, 1988;Mingolla & Todd, 1986;Todd & Mingolla, 1983;Todd & Reichel, 1991). These experiments indicated that human observers are very poor at this.…”

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confidence: 99%

“…Several psychophysical experiments report observers' ability to estimate local surface structure from shading (Biilthoff & Mallot, 1988;Mingolla & Todd, 1986;Todd & Mingolla, 1983;Todd & Reichel, 1991). These experiments indicated that human observers are very poor at this.…”

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confidence: 99%

“…Other experiments have shown that observers cannot distinguish local shapes such as concave and convex spheres when they do not know the illuminant direction (Berbaum, Bever, & Sup Chung, 1984;Ramachandran, 1988). In most of these studies, a very restricted set of shapes such as spheres (Berbaum et al, 1984), cylinders (Todd & Mingolla, 1983), or ellipsoids (Biilthoff & Mallot, 1988;Mingolla & Todd, 1986) have been used. Here, we investigate whether human observers are able to categorize a wide range of local shapes (elliptic, hyperbolic, and cylindric) on the basis of shading and the possible effect of information about the illuminant direction on the responses.…”

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Perception of local shape from shading

Erens

Kappers

Koenderink

1993

Perception & Psychophysics

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Theoretically, metric solid shape is not determined uniquely by shading. Consequently, human vision has difficulty in categorizing shape when shading is the only cue. In the present research, subjects were required to categorize shaded quadric surfaces. We found that they were rather poor at this task; they confused hyperbolic and elliptic (both convex and concave) shapes easily. When a cast shadow visually indicated the direction of the illuminant, they were able to notice the concavity or convexity of elliptic shapes. However, they still confused elliptic and hyperbolic ones. Finally, when an animated sequence of eight intensity patterns belonging to one quadric shape had been displayed, the subjects were able to categorize the quadrics. However, the results are still quite moderate. Our experiments indicate that local shading structure is only a weak shape cue when presented in the absence of other visual cues. 145With the present generation of rendering algorithms, it is apparently relatively easy to generate very "natural" images on a computer screen. The three-dimensional impression created by these images is very compelling. However, such an informal observation has to be quantified. Very little research has been done on the perception of solid shape on the basis of shading.Computer images provide several visual cues that potentially contribute to the perception of solid shape (Gibson, 1950). The role of shading in these images is complicated because extracting shape from shading is not a trivial task. The shading is determined by the surface orientation, the illuminant direction, and the surface properties. This means that the same luminance distribution can be generated by several different surfaces. For instance, the luminance distribution of concave and convex spheres is exactly the same. Thus, in order to find the local surface structure on the basis of shading, one has to make assumptions about the illuminant direction and the surface properties (Horn, 1975(Horn, , 1977Pentland, 1984Pentland, , 1989. Another method to estimate the local surface structure from shading is to combine the information given by several intensity patterns of one shape (Woodham, 1980). Most computational theories on shape from shading calculate the surface shape locally (Horn, 1975(Horn, , 1977Pentland, 1984Pentland, , 1989Woodham, 1980). It is not clear whether human observers are able to judge the local shape of an object on the basis of shading.Several psychophysical experiments report observers' ability to estimate local surface structure from shading (Biilthoff & Mallot, 1988;Mingolla & Todd, 1986;Todd & Mingolla, 1983;Todd & Reichel, 1991). These experiments indicated that human observers are very poor at this. Other experiments have shown that observers cannot distinguish local shapes such as concave and convex spheres when they do not know the illuminant direction (Berbaum, Bever, & Sup Chung, 1984;Ramachandran, 1988). In most of these studies, a very restricted set of shapes such as spheres (Berbaum et al., 1984), ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Perception of local shape from shading

Erens

Kappers

Koenderink

1993

Perception & Psychophysics

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“…Requests for reprints and other correspondence should be sent to V. S. Ramachandran, Psychology Department 0109, University of California, San Diego, La Jolla, CA 92093-0109. thought about this problem, there have been only a small handful of systematic psychological studies on it (Berbaum, Bever, & Chung, 1983;Brewster, 1847;Howard, 1983;Ramachandran, 1988a, l988b;Rittenhouse, 1786;Todd & Mingolla, 1983).…”

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Perception of shape from shading

Ramachandran

1988

Nature

634

380

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The extraction of three-dimensional shape from shading is one of the most perceptually compelling, yet poorly understood, aspects of visual perception. In this paper, we report several new experiments on the manner in which the perception of shape from shading interacts with other visual processes such as perceptual grouping, preattentive search ("pop-out"), and motion perception. Our specific findings are as follows: (1) The extraction of shape from shading information incorporates at least two "assumptions" or constraints-first,that there is a single light source illuminating the whole scene, and second, that the light is shining from "above" in relation to retinal coordinates. (2) Tokens defined by shading can serve as a basis for perceptual grouping and segregation. (3) Reaction time for detecting a single convex shape does not increase with the number of items in the display. This "pop-out" effect must be based on shading rather than on differences in luminance polarity, since neither left-right differences nor step changes in luminance resulted in pop-out. (4) When the subjects were experienced, there were no search asymmetries for convex as opposed to concave tokens, but when the subjects were naive, cavities were much easier to detect than convex shapes. (5) The extraction of shape from shading can also provide an input to motion perception. And finally, (6) the assumption of "overhead illumination" that leads to perceptual grouping depends primarily on retinal ratherthanon "phenomenal" or gravitational coordinates. Taken collectively, these findings imply that the extraction ofshapefrom shading is an "early" visual process that occurs prior to perceptual grouping, motion perception, and vestibular (as well as "cognitive") correction for head tilt. Hence, there may be neural elements very early in visual processing that are specialized for the extraction of shape from shading.We use three-dimensional (3-D) depth perception to find our way around the world and to manipulate objects that we encounter. Although the retinal image is two-dimensional, somehow the brain is able to use the information from this image to yield an experience of solidity and depth.Of the numerous mechanisms used by the visual system to recover the third dimension, the ability to use shading is probably phylogenetically one of the most primitive. One reason for believing this is that in the natural world, animals have often evolved the principle of countershading to conceal their shapes from predators; they have pale bellies that serve to neutralize the effects of the sun shining from above (Thayer, 1909). The prevalence of countershading in a variety of animals (including fishes) suggests that shading must be a very important source of information about 3-D shapes.Although artists have long recognized the importance of shading, there have been few studies of how the human visual system actually extracts and uses this information. Since the time when Leonardo da Vinci first thought about this problem, there have been only a small ha...

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Perceived illumination measured

Петров¹,

Kweon

et al. 1998

Color Res. Appl.

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We consider a method of measurement of apparent illumination using the perceptual phenomenon of fluorescence to which we give a psychophysical explanation based on the hypothesis of direct relation of perception of self‐luminosity to the apparent illumination of the scene observed by the viewer. We report results of three experimental studies: (1) measurements of apparent illumination when a flat mondrian in the darkness is observed; (2) measurements of apparent illumination in a “rich” 3D scene; (3) testing linearity of the subjective illumination space. Based on the obtained data, we confirm the basic hypothesis of a relation between the self‐luminosity phenomenon and the perceived illumination, and show that the suggested method of measurement of apparent illumination gives reliable and accurate (errors were in the range 4–10%) values of its chromatic components. Apparent illumination in the case of a mondrian observed in the darkness is found unstable, which can be expected given that the context of such a scene is insufficient for obtaining a unique solution for all the components of the photometric problem. In the second experiment, we show that the measurement results remain constant when the context of a “rich” 3D scene is changed and that they follow the changes in illumination conditions. In the third experiment, we study the composition of different illuminations and show that the simple relation f = f1 + f2 holds for the measurement of the illumination (f) when two other illuminations (f1, f2) are applied simultaneously. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 159–168, 1998

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Perception of surface curvature and direction of illumination from patterns of shading.

Cited by 147 publications

References 11 publications

Perception of local shape from shading

Perception of local shape from shading

Perception of shape from shading

Perceived illumination measured

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