DISTORTIONS OF DEPTH-ORDER RELATIONS AND PARALLELISM IN STRUCTURE-FROM-MOTION

Four experiments related human perception of depth-order relations in structure-from-motion dis plays to current Euclidean and affine theori es of depth recovery from motion. Discrimination between parallel and nonparallel lines and relative-depth judgments was observed for orthog raphic projections of rigidly oscillating random-dot surfaces. We foun d that (1) depth-order relations were perceived veridically for surfac es with the same slant magnitudes, but were systematically biased for surfaces with different slant magnitudes. (2) Parallel (virtual) Lines defined by probe dots on surfaces with different slant magnitudes wer e judged to be nonparallel. (3) Relative-depth judgments were internal ly inconsistent for probe dots on surfaces with different slant magnit udes. It is argued that both veridical performance and systematic misp erceptions may be accounted for by a heuristic analysis of the first-o rder optic flow.