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Ying Yu, James Todd, Alexander Petrov; Changes in Viewing Distance Produce Systematic Distortions of the Apparent 3D Shapes of Symmetric Polyhedra. Journal of Vision 2018;18(10):720. doi: 10.1167/18.10.720.
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Prior studies have shown that the perceived depth from binocular disparity becomes increasingly compressed as the viewing distance increases. Because of this perceptual distortion, two objects with the same 3D shape are predicted to have different apparent shapes when viewed simultaneously from non-matching distances: The far object should appear compressed in depth relative to the near object. Method: To test these hypotheses, computer-generated stereoscopic images of mirror-symmetric 3D polyhedra, similar to the stimuli of Li et al. (2011, doi:10.1167/11.4.11), were viewed binocularly through shutter glasses. On each trial, two such polyhedra were presented side by side against a black background on a LCD monitor, and each of these objects was positioned independently at a viewing distance of 100 cm ("near") or 200 cm ("far"). The stimuli differed in size and were rendered in the same 3D orientation relative to the cyclopean eye of the observer. The reference polyhedron had a fixed 3D shape. The test object was scaled in depth relative to the reference, and this scaling could be adjusted by observers. The task on each trial was to adjust the test object so that it appeared to have the same 3D shape as the reference. Results: The group-averaged Z-scaling was approximately 30% higher in the far-test/near-reference condition than in the near-test/far-reference condition. By contrast, the Z-scaling was approximately equal in the two equidistant conditions. This indicates equivalent perceptual distortions for both objects at a common distance. Moreover, the scaling in the equidistant conditions was approximately halfway between the adjustments in the two non-equidistant conditions, as predicted. Overall, these results suggest that 3D shape perception is systematically distorted even for compact symmetric polyhedral objects in a shape matching task, which contrasts sharply with the theoretical predictions of Li et al. (2011).
Meeting abstract presented at VSS 2018
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