Asymmetrical Effect of Crossed and Uncrossed Disparity on Stereoscopic Capture

When a real or subjective contour is superimposed on a repetitive texture or ‘wallpaper pattern’, the apparent depth of the elements of the wallpaper pattern may be influenced by the contour. When the contour has crossed disparity, the elements inside the contour are seen floating in the plane of the contour. This is called ‘stereoscopic capture’. On the other hand, when the contour has uncrossed disparity a different, somewhat unstable, percept is seen. The wallpaper elements are either seen to form a transparent surface floating in front of the contour, or all of the elements inside and outside of the contour are seen to lie in the uncrossed plane of the inducing contour. We suggest that the asymmetry between crossed and uncrossed stereo capture is a by-product of the different roles played by crossed and uncrossed disparity in stereoscopic surface construction: specifically, crossed and, perhaps, zero disparity spreads one-directionally into a figure from a contour whereas uncrossed disparity spreads out from a figure in all directions. These points are illustrated with a series of demonstrations.