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Jenny Bartov, Martin Giesel, Qasim Zaidi; Exploring the veridicality of shape-from-shading for real 3D objects. Journal of Vision 2015;15(12):964. doi: 10.1167/15.12.964.
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© ARVO (1962-2015); The Authors (2016-present)
Despite the large number of shape-from-shading studies, the degree of veridicality with which observers perceive real 3D objects has not been examined. Six observers viewed sinusoidal, triangular and trapezoidal corrugations made from gray cardboard of approximately uniform reflectance- presented either fronto-parallel or 33 degrees in slant. The object, placed inside a box, was illuminated from its top-left or left by a point light source. The corrugations were seen through an aperture that masked their terminating contours and the light source. Observers' were asked to draw the depth profile of the object as if it were seen from above. Using a computer mouse, they drew on a computer screen placed just below the object. The drawing area had the same size as the aperture through which the object was seen. Observers also indicated the orientation of the object and the location of the light source. In the first condition, the objects were viewed monocularly; in the second, a white matte sphere was placed in front of the object to help in locating the light; in the third, the task was repeated with binocular viewing. Drawings revealed that observers were quite accurate in inferring the objects’ shapes when viewing binocularly. There was more variability among the observers when objects were viewed monocularly, with some systematic trends: 1. Many observers were able to recreate the veridical shapes despite monocular viewing, 2. The drawn shapes often differed from the shape of the luminance variations across the objects, thus rejecting heuristics such as “dark is deeper”, 3. The slanted triangular corrugation was often confused with the trapezoidal and vice versa, as areas of uniform luminance could be interpreted as fronto-parallel or slanted. Detailed analyses of the drawings suggest possible heuristics that different observers might use to infer the shapes of the corrugations from shading variations.
Meeting abstract presented at VSS 2015
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