2½-D sketch

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In the computational theory of vision pioneered in the late 1970s by the English psychologist David Courtenay Marr (1945–80), the second stage in the perceptual process after the primal sketch, incorporating orientation and depth cues relative to the viewpoint of the observer, but providing a representation (2) that is insufficiently abstract for object recognition, because it is viewer-centred rather than being invariant with respect to the observer's viewpoint. Compare 3-D model description, primal sketch. [So called because although it is a three-dimensional representation, it provides insufficient information for visual recognition of three-dimensional objects]

Subjects: Psychology.

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