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Sabrina Hansmann-Roth, Pascal Mamassian; Lack of glossiness constancy with viewpoint changes . Journal of Vision 2014;14(10):454. doi: https://doi.org/10.1167/14.10.454.
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The presence of a bright, specular highlight is one of the most important factors in gloss perception. Previous work has shown that even when highlights cover only a small region on a surface, they lead to the impression that an object has a uniform surface material (Beck 1981, Percept. Psychophys.). In the present study we investigate whether perceived glossiness changes depending on the observersâ€™ viewpoint. A single, large, mostly fronto-parallel surface was cut in 49 parts and each part was presented one at a time. The surface contained periodic structural elements in relief so that each part included the same structures but at different spatial locations. Each resulting stimulus image had a 50 % overlap with the neighboring image. The participantâ€™s task was to compare the presented stimulus image with 7 calibrated probe images and select the probe that had the most similar gloss to the stimulus. Each stimulus was presented for 2 s at the spatially correct position on the computer monitor. Our results indicate that perceived glossiness changes over the surface. From the data we computed a glossiness map that corresponds to the mean glossiness ratings for each part of the surface. Glossiness ratings varied over the surface indicating that gloss is not perceived equally on the surface. Since all stimuli were part of one periodic image, light source and 3D geometry were identical, however the viewing direction was different for each point on the surface. Therefore highlight-structure varies at different parts of the surface. Controlled experiments were run to test whether these changes in highlight shape and size were interpreted as changes in the material properties and not as an artifact produced by the viewing direction or other change that occurs with a different viewing direction. In summary, gloss constancy does not seem to occur with viewpoint changes.
Meeting abstract presented at VSS 2014
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