Depth of monocular elements in a binocular scene: the conditions for da Vinci stereopsis.

Quantitative depth based on binocular resolution of visibility constraints is demonstrated in a novel stereogram representing an object, visible to 1 eye only, and seen through an aperture or camouflaged against a background. The monocular region in the display is attached to the binocular region, so that the stereogram represents an object which is only partially visible to the eye that sees it. The results show that this feature is necessary for quantitative depth, which is not found for a fully visible monocular object in the same location, and that depth in these displays, although very precise, is not based on fusional Stereopsis. The findings provide clear support for the existence of a process of da Vinci Stereopsis, but one more sophisticated than the one proposed by K. Nakayama and S. Shimojo (1990).