Figure 8.

Depth from oblique disparities. (A) Schematic example of the stimuli used by Patel et al. (2003). The central squares within the RDSs have oblique disparity within two 30°-wide directional bands (θ). The centers of these bands are ±30° in the upper RDS and ±45° in the lower RDS. Oblique arrows represent 90° phase disparities at one spatial scale for components at the extremes of these bands (i.e., disparities perpendicular to central random-dot components with orientations between 105° and 135° and between 45° and 75° in the upper RDS). These component disparities would be found in a RDS having the horizontal disparity given by the IOC lines and proportionally covering the range of the gray arrow. Other components at a larger or smaller scale, also with 90° phase disparities, would extend this range to greater and smaller values. All components outside the disparate orientation range had zero disparity, as did the entire surrounding RDS; disparities are not drawn to scale. The observers in the study by Patel et al. (2003) matched the perceived depth of the inner square of the RDS by adjusting the disparity of a simultaneously displayed and overlapping 3′ × 3′ square probe. (B) Mean depth matching disparities plotted as a function of the central direction of the component disparities; a disparity direction of –75° comes from components centered on an orientation of 15°. The inverse cosine of orientation is pinned to the data point for θ of 30° and center disparity direction of 15°. Both the center orientation of the disparate bands and their bandwidth affect perceived depth, which dissipates as the disparity direction nears vertical. (Panel B was adapted from Patel et al., 2003.)