Types of shear disparity and the perception of surface inclination.
A study is reported of (i) the perceived inclination of a textured surface in depth about a horizontal axis as a function of disparity magnitude for horizontal-shear disparity, vertical-shear disparity, and rotation disparity; and (ii) interactions between patterns with shear or rotation disparity and superimposed or adjacent patterns or lines with zero disparity. Horizontal-shear disparity produced strong inclination which was enhanced by superimposed or adjacent zero-disparity stimuli. It produced little or no inclination contrast in superimposed or adjacent zero-disparity stimuli. Vertical-shear disparity produced inclination in the opposite direction (induced effect) which was reduced to near zero by a superimposed zero-disparity pattern. Adjacent vertical-shear and zero-disparity patterns appeared inclined at slightly different angles with a wide curved boundary. This suggests that vertical-shear disparities are averaged over a wide area. Rotation disparity produced minimal inclination. A superimposed or adjacent zero-disparity line appeared strongly inclined. A superimposed or adjacent zero-disparity pattern appeared vertical and caused the pattern with rotation disparity to appear inclined. Four mechanisms are proposed to account for the results: depth contrast, depth enhancement, deformation-disparity processing, and disparity transfer arising from cyclovergence.
Centre for Vision Research, York University, Ontario, Canada. ihoward@hpl.ists.ca
I P
IP
Howard
B J
BJ
Pierce
D003201:Computers; D003867:Depth Perception / Q000502:physiology; D005556:Form Perception / Q000502:physiology; D006801:Humans; D011581:Psychological Tests; D014796:Visual Perception / Q000502:physiology*