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Symmetry 2018, 10(8), 344;

Perception of 3D Symmetrical and Nearly Symmetrical Shapes

Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA
School of Psychology, National Research University Higher School of Economics, Moscow 109316, Russia
Department of Cognitive Sciences, University of California-Irvine, Irvine, CA 92697, USA
Author to whom correspondence should be addressed.
Received: 17 July 2018 / Revised: 8 August 2018 / Accepted: 13 August 2018 / Published: 16 August 2018
(This article belongs to the Special Issue Symmetry-Related Activity in Mid-Level Vision)
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The human visual system uses priors to convert an ill-posed inverse problem of 3D shape recovery into a well-posed one. In previous studies, we have demonstrated the use of priors like symmetry, compactness and minimal surface in the perception of 3D symmetric shapes. We also showed that binocular perception of symmetric shapes can be well modeled by the above-mentioned priors and binocular depth order information. In this study, which used a shape-matching task, we show that these priors can also be used to model perception of near-symmetrical shapes. Our near-symmetrical shapes are asymmetrical shapes obtained from affine distortions of symmetrical shapes. We found that the perception of symmetrical shapes is closer to veridical than the perception of asymmetrical shapes. We introduce a metric to measure asymmetry of abstract polyhedral shapes, and a similar metric to measure shape dissimilarity between two polyhedral shapes. We report some key observations obtained by analyzing the data from the experiment. A website was developed with all the shapes used in the experiment, along with the shapes recovered by the subject and the shapes recovered by the model. This website provides a qualitative analysis of the effectiveness of the model and also helps demonstrate the goodness of the shape metric. View Full-Text
Keywords: 3D shape perception; symmetry prior; shape perception model; inverse problem 3D shape perception; symmetry prior; shape perception model; inverse problem

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Jayadevan, V.; Sawada, T.; Delp, E.; Pizlo, Z. Perception of 3D Symmetrical and Nearly Symmetrical Shapes. Symmetry 2018, 10, 344.

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