Stereoscopic occlusion junctions

Portions of surfaces in a binocularly viewed scene may be 'half occluded', that is, visible in only one eye. The human visual system uses zones of hal f occlusion to help segment the visual scene and infer figure-ground relati onships at object boundaries. We developed a quantitative model of the dept h-discontinuity cue provided by half occlusion. Half occlusions are reveale d by two-dimensional interocular displacements of binocularly viewed occlus ion junctions, such as T junctions. We derived a formula relating this two- dimensional displacement, or 'pseudodisparity', to binocular disparities an d orientations of occluding and occluded contours. In human psychophysical experiments, perceived depth and contour orientation quantitatively depende d on pseudodisparity, as predicted by our model, implying that the visual s ystem senses quantitative variations in interocular junction position to re construct occlusion geometry.