 Occlusion in stereo vision

Occlusion in stereo vision occurs when a scene feature visible from one camera is hidden behind another surface from the second viewpoint. Such a feature has no visible partner, even if camera calibration is exact. Stereo correspondence must allow unmatched locations instead of forcing every image location to have a partner.^[ref]

Consider a nearby post in front of a distant wall. Moving the viewpoint sideways shifts the post's projection more than the wall's because their depths differ. A strip of wall exposed beside the post in one image can therefore be covered in the other. Matching that strip to the post invents a depth belonging to the wrong surface. Missing-value masks and consistency checks can help represent this limitation, while smoothing a disparity map across the boundary can conceal it rather than recover the hidden wall.