Abstract
A fundamental problem for the perception of 3D shape from shading is to achieve some level of constancy over variations in the pattern of illumination. The present research was designed to investigate how changes in the direction or manner of illumination influence the apparent shapes of surfaces. The stimuli included 3D objects with Lambertian reflectance functions that were illuminated by hemispheric dome lights, rectangular area lights, or point light sources. The directions of illumination were also systematically manipulated. All stimuli had exactly the same bounding contours so that those contours provided no information for distinguishing the different possible surfaces. Observers judged the 3D shapes of these surfaces by marking local depth minima and maxima along designated scan lines using a hand held mouse. The results revealed that the local depth extrema were shifted slightly toward the direction of illumination, but these changes were much smaller than what would be expected based on differences in the pattern of luminance among the stimulus images. These findings demonstrate that there is a substantial amount of illumination constancy in the perception of 3D shape from shading, but that it is not perfect. Several hypotheses are considered about how this constancy could potentially be achieved.
Meeting abstract presented at VSS 2016