= 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.<Disparity map post-filtering in the OpenCV documentation>[Introduction, half-occlusions, depth discontinuities and invalidating inaccurate disparities]{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.
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