Abstract
The difference between two monocular views of a horizontal line can result in either a complete matching or an incomplete matching. The complete matching is consistent with the perception of a line slanted in depth while the incomplete matching is consistent with the perception of a partially occluded line. Without other cues both complete and incomplete matching are possible resulting in an ambiguous perception of the line which could be either slanted in depth or partially occluded. This study investigated whether a complete matching of local features would affect the matching of horizontal lines in stereopsis and disambiguate the perception. A CrystalEyes 3 Workstation was used to produce the stereo images on a ViewSonic CRT monitor, 140Hz in refresh rate and 1024*768 in resolution. In the experimental displays, horizontal lines were presented to each eye with inter-ocular differences that are consistent with both slant perception and occlusion perception. Vertical lines were presented in between the horizontal lines which specified a unique local matching. In Experiment 1, the vertical lines were presented followed by the presentation of the horizontal lines. In Experiment 2, the vertical lines were presented simultaneously with the horizontal lines. In both Experiments, the vertical lines were manipulated such that they were presented either in a fronto-parallel plane or in a plane slanted in depth. The subjects were asked to judge the perceived slant of the horizontal lines. The results showed that the matching of vertical lines is propagated by the visual system to that of horizontal lines. The matching of local features determined whether slanted lines or partially occluded lines should be perceived from the differences between the left and right views of horizontal lines.