OCCLUSION CONSTRAINTS AND STEREOSCOPIC SLANT

In binocular vision horizontal magnification of one retinal image lead s to a percept of three-dimensional slant around a vertical axis. It i s demonstrated that the perception of slant is diminished when an occl usion interpretation is possible. A frontoparallel plane located in th e immediate vicinity of a slanted surface in a location which allows a perception of occlusion reduces the magnitude of perceived slant sign ificantly. When the same plane is placed on the other side, the slant perception is normal because there is no alternative occlusion interpr etation. The results indicate that a common border between the occlude r and a slanted surface is not a necessary condition for the reduction effect, If the edges are displaced and the edge of the slanted surfac e is placed in a location in which it could be occluded, the effect st ill appears.