Perception of local shape from shading

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 ta...

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Bibliographic Details
Published inPerception & psychophysics Vol. 54; no. 2; p. 145
Main Authors Erens, R G, Kappers, A M, Koenderink, J J
Format Journal Article
LanguageEnglish
Published United States 01.08.1993
Subjects
Algorithms
Attention
Contrast Sensitivity
Depth Perception
Discrimination Learning
Female
Humans
Male
Orientation
Pattern Recognition, Visual
Psychophysics
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Summary: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.
ISSN:0031-5117
DOI:10.3758/BF03211750