FIGURE 1. Top view of the geometry of the binocular matching problem.

The intersections of the visual lines indicate the locations of possible matches. The drawing is schematic; contours in three dimensions introduce another dimension of ambiguity (namely, determining how correspondence between portions of the contours in the two eyes should be defined). One configuration represents a large depth range (black dots), the other a small depth range (white dots). The two configurations create identical sets of visual lines.