The venetian-blind effect: a preference for zero disparity or zero slant?

Abstract

When periodic stimuli such as vertical sinewave gratings are presented to the two eyes, the initial stage of disparity estimation yields multiple solutions at multiple depths. The solutions are all frontoparallel when the sinewaves have the same spatial frequency; they are all slanted when the sinewaves have quite different frequencies. Despite multiple solutions, humans perceive only one depth in each visual direction: a single frontoparallel plane when the frequencies are the same and a series of small slanted planes—Venetian blinds—when the frequencies are quite different. These percepts are consistent with a preference for solutions that minimize absolute disparity or overall slant. The preference for minimum disparity and minimum slant are identical for gaze at zero eccentricity; we dissociated the predictions of the two by measuring the occurrence of Venetian blinds when the stimuli were viewed in eccentric gaze. The results were generally quite consistent with a zero-disparity preference (Experiment 1), but we also observed a shift toward a zero-slant preference when the edges of the stimulus had zero slant (Experiment 2). These observations provide useful insights into how the visual system constructs depth percepts from a multitude of possible depths.

Mechanisms for similarity matching in disparity measurement

“…Cross-correlation models exhibit performance consistent with minimal relative disparity matching (Goutcher and Hibbard, 2010; Vlaskamp et al, 2013), disparity gradient limits (Filippini and Banks, 2009) and coarse-scale luminance and contrast similarity matching (Anderson and Nakayama, 1994; Goutcher and Hibbard, 2010), even though such models do not explicitly apply these rules for matching. Our results show, however, that the similarity-based matching emerging from the cross-correlation model differs markedly from results for human observers.…”

Stereopsis is adaptive for the natural environment

“…The upper left panel of Fig. 7B shows that local cross-correlation of the images yields equally high-correlation peaks for numerous horizontal disparities ( 39 ). The same behavior is observed in disparity-selective cortical neurons: When presented with periodic stimuli, V1 neurons exhibit multiple response peaks ( 54 ).…”

“…The nonuniform allocation is manifest by pairs of retinal points with special status. These corresponding-point pairs are special because (i) binocular matching solutions between the two eyes’ images are biased toward them ( 37 – 39 ); (ii) the region of single, fused binocular vision straddles them ( 40 , 41 ); and (iii) the precision of stereopsis is greatest for locations in space that project to those points ( 42 – 46 ). The horopter is the set of locations in 3D space that project onto corresponding retinal points and therefore comprise the locations of finest stereopsis ( 47 , 48 ).…”

“…These effects have been attributed to smoothness constraints embodied in the neural computation of disparity ( 5 , 58 ). However, the percepts with venetian blinds stimuli are definitely not smooth ( 39 ), which suggests that another principle is involved. We hypothesized that prior assumptions about the most likely disparities significantly influence the percepts in these illusions.…”

Depth Artifacts Caused by Spatial Interlacing in Stereoscopic 3D Displays

“…Good matching features are found equally on both sides of the edge, which makes the percept ambiguous. The repeating pattern created by interlacing produces an image that is similar to the wallpaper illusion (Brewster, 1844;Vlaskamp et al, 2013), in which a repeating pattern creates a perception of depth. The nearest neighbor rule (Arditi et al, 1981) states that the visual system fuses the closest matching features to minimize the absolute disparity; however, this rule applies only in the absence of other images.…”