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James Todd, Farley Norman; The interaction between surface roughness and the illumination field on the perception of metallic materials. Journal of Vision 2017;17(10):227. doi: https://doi.org/10.1167/17.10.227.
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© ARVO (1962-2015); The Authors (2016-present)
An important phenomenon in the study of human perception is the ability of observers to identify different types of surface materials. One factor that complicates this process is that materials can be observed with a wide range of surface geometries and light fields. The present research was designed to examine the influence of these factors on the appearance of metal. The stimuli depicted three possible objects that were illuminated by three possible light fields. These were generated by a single point light source, 2 rectangular area lights, or projecting light onto a translucent white box that contained the object (and the camera) so that the object would be illuminated by ambient light in all directions. The materials were simulated using measured parameters of chrome with four different levels of roughness. Observers rated the metallic appearance and shininess of each depicted object using two sliders. The highest rated appearance of metal and shininess occurred for the surfaces with the lowest roughness in the ambient light field, and these ratings dropped systematically as the roughness was increased. For the objects illuminated by point or area lights, the appearance of metal and shininess were significantly less than in the ambient conditions for the lowest roughness value, and significantly greater than in the ambient condition for intermediate values of roughness. We also included a control condition depicting objects with a low roughness and a porcelain reflectance function that had both Lambertian and specular components. These objects were rated as highly shiny but they did not appear metallic. An analysis of the luminance patterns in these images revealed that the primary difference between metal and porcelain occurs near smooth occlusion boundaries, thus suggesting that these regions provide critical information for distinguishing different types of shiny materials.
Meeting abstract presented at VSS 2017
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