Abstract
We investigate the perception of three-dimensional structure from shading when contour is not given or contour gives ambiguous convex/concaveness. It is crucial to separate contour and shading in order to examine 3D perception purely from shading, and the interaction between contour and shading. We developed stimuli whose 3D structure is generated based on Gaussian or white-noise so that their saliency of contour is controlled. Psychophysical experiments were carried out using the stimuli and the following results were obtained. (1)Contour is dominant for 3D perception comparing to shading even if contour is ambiguous, (2)even if stereopsis gives 3D structure, shading is dominant if contour is invisible, (3)not only monotonic gradation of grayness gives shape-from-shading but also the global changes in local contrast.
