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Farley Norman, James Todd; Effects of illumination on the perceptual categorization of surface materials. Journal of Vision 2018;18(10):887. doi: 10.1167/18.10.887.
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© ARVO (1962-2015); The Authors (2016-present)
An important problem in the study of human perception is to understand how it is possible to identify different types of surface materials. One factor that complicates this issue is that materials can be observed with many different patterns of illumination. The present research was designed to examine how this affects the abilities of observers to categorize metal, shiny black materials and shiny white materials. The stimuli depicted three possible objects that were illuminated by five possible HDRI light maps. These light maps were chosen so that they varied significantly in the overall range of illuminant directions, and their intensities were also systematically manipulated. The surfaces included a low roughness chrome material, a shiny black plastic material, and a shiny white plastic material with both diffuse and specular components. Observers rated each stimulus by adjusting four sliders to indicate their confidence that the depicted material was metal, shiny black, shiny white or something else, and these adjustments were constrained so that the sum of all four settings was always 100%. The results revealed that these categories are easily confused. For example, metal materials with low intensity light maps or a narrow range of illuminant directions are often judged as black plastic. Similarly, black plastic materials with high intensity light maps or a very wide range of illuminant directions are often judged as white plastic or metal. In an effort to explain these results, we propose that the perceptual categorization of shiny materials is heavily influenced by image contrast and the overall proportion of a visible surface that is covered by specular highlights.
Meeting abstract presented at VSS 2018
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