The Effects of Smooth Occlusions and Directions of illumination on the Visual Perception of 3D Shape from Shading
53.3026, Tuesday, 19-May, 8:30 am - 12:30 pm, Banyan Breezeway
Eric Egan1, James Todd1, Christopher Kallie1; 1Psychology, The Ohio State University
Human observers made local orientation judgments of smoothly shaded surfaces illuminated from different directions by large area lights, both with and without visible smooth occlusion contours. Test-retest correlations between the first and second halves of the experiment revealed that observers’ judgments were highly reliable with a residual error of only 2%. Over 88% of the variance between observers’ judgments and the ground truth could be accounted for by an affine correlation, but there was also a systematic non-affine component that accounted for approximately 10% of the perceptual error. The presence or absence of visible smooth occlusion contours had a negligible effect on performance, but there was a small effect of the illumination direction, such that the response surfaces were sheared slightly toward the light source. These shearing effects were much smaller, however, than the effects produced by changes in illumination on the overall pattern of luminance or luminance gradients. Implications of these results for current models of estimating 3D shape from shading are considered.