The effects of illumination direction on the perception of 3D shape from shading

3rd Place at the Denman Undergraduate Research Forum 2016A 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 of illumination influence the apparent shapes of surfaces. The stimuli included images of 3D surfaces with Lambertian reflectance functions that were illuminated by a rectangular area light source. The direction of illumination was systematically manipulated. Observers judged the 3D shapes of these surfaces by marking local depth minima and maxima along three designated scan lines using a hand-held mouse. The results revealed that the local depth maxima were shifted slightly toward the direction of illumination, while the local depth minima were shifted slightly away from the direction of illumination. However, 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.No embargoAcademic Major: Psycholog