Disparity statistics inform the perception of material for glossy objects A Muryy, A Welchman, R Fleming |
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School of Psychology, University of Birmingham, United Kingdom
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| Specular (“glossy”) objects create stereo-signals with specific properties that differ significantly from Lambertian (“matte”) surfaces. Does the visual system use these stereo-cues to identify the material properties of objects? We identified potential stereoscopic cues to surface gloss by calculating the disparity fields generated by irregularly shaped Lambertian and specular objects. We found that specular objects give rise to specific and unusual features: 1) specular disparity fields may have discontinuities and un-fusible or barely fusible regions; 2) patterns of vertical disparities are quite unusual in their magnitude and distribution. We then conducted psychophysical judgments of gloss to test the role of these signals in material perception. Using a specialised rendering procedure, we systematically morphed between stimuli with Lambertian vs. Specular properties, while holding monocular cues constant. We presented stimuli from this morphing space to obtain thresholds for “glossy” and “matte” appearance (8 participants, adaptive threshold estimation procedure). We found that objects appeared glossy in a large area of this morphing space, consistent with the use of the unusual disparity signals, but not with the true physical properties of specular reflection. Additional analysis found limited evidence for interocular intensity and contrast sign differences, suggesting ‘binocular lustre’ is less important than disparity properties. |
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