Fig. 3.

The normalized frequency of occurrence of the physical sources of angles with various subtenses, given the presence of the physical source of a horizontal (Left), oblique (Center), or vertical (Right) reference line. The distributions were obtained from the range-image database by applying appropriate geometrical templates as indicated in Fig. 2. The icons below the graphs indicate the orientations of the reference-line (black) and second-line (gray) templates. Note that results obtained from fully natural scenes (Upper) are not significantly different than those from “carpentered” environments (Lower).