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Dicle Dovencioglu, Maarten Wijntjes, Ohad Ben-Shahar, Katja Doerschner; Perceived bumpiness of 3D-rotating objects are affected by surface reflectance and motion characteristics. Journal of Vision 2016;16(12):945. doi: 10.1167/16.12.945.
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© 2017 Association for Research in Vision and Ophthalmology.
The visual system exploits dynamic visual information (optic flow) falling onto the retina when inferring 3D shape. A matte (diffusely-reflecting) moving object conveys visual information about objects motion and its first order shape properties; while the flow from a specular object carries information about the local and global curvature characteristics (second-order shape) and the surface reflectance (Koenderink and van Doorn, 1980). Dovencioglu et al. (2015) showed that the flow of information from matte and specular objects yields differences in perceived local curvature category. Here, we test whether judging 3D curvature magnitude is different for matte and specular objects in dynamic scenes. We asked observers to judge bumpiness of the two consecutive objects in two 2IFC experiments. In Experiment 1, observers compared various test objects to a reference object of specular reflectance and of intermediate bumpiness. In Experiment 2, reference object had matte-textured reflectance. Objects were created by protruding spheres with random sinusoids, and bumpiness level was controlled by the amplitude of the sinusoids. In total, 14 observers completed each experiment (n=28) with bumpiness (5) x material (3: specular, matte, mixed) x motion (3 rotation axes) conditions. By comparing the "proportions judged bumpier" we have observed that in general bumpiness judgements are more difficult for specular objects than for matte. Also, the judgment seemed easier when the reference and test objects had the same surface reflectance. Matte objects were judged less bumpy when rotating around the viewing direction as compared to in-plane rotations regardless of the reference objects' surface reflectance (Exp 2), where specular objects were not susceptible to these rotation axis manipulations (Exp 1). In summary, specular flow can be a robust cue for estimating 3D shape as unlike matte flow it is not affected by different types of object motion.
Meeting abstract presented at VSS 2016
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