FIGURE 2. Experimental procedure.
From the following article:
Motion direction, speed and orientation in binocular matching
Raymond van Ee and Barton L. Anderson
Nature 410, 690-694(5 April 2001)
doi:10.1038/35070569
The stimulus consisted of a collection of frontoparallel bars (a) with disparities specifying a volume that evoked a percept of a three-dimensional volume of bars (b). Observers matched the perceived depth-to-width ratio evoked by the stimulus with the aspect ratio of the outline rectangle (c).