Environment maps and the perception of shape from mirror reflections M Langer, A Faisman |
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School of Computer Science, McGill University, QC, Canada
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| Perceiving the shape of a smoothly curved mirror surface is a challenging task because the image intensities are determined both by the surface shape and by the surrounding environment. Here we extend our recent study of the perception of qualitative shape from highlights and mirror reflections [Faisman and Langer, Journal of Vision (in press)] by more closely examining how shape percepts of mirror surfaces depend on the parameters of the environment map. We generated smooth, bumpy terrain surfaces using computer graphics and presented them slanted as a floor or ceiling. The surfaces were illuminated using environment maps that included 1/f noise and a near regular soccer ball pattern. The brightnesses of these environment maps were modulated with low frequency spherical harmonics to give them a dominant direction which produced a shading-like effect similar to soft gloss. Our main finding is that varying the dominant direction of the environment brightness relative to the global slant of the terrain significantly affected subject’s performance in judging qualitative shape. The effect is similar to (but subtly distinct from) the classical prior for light from above for matte surfaces. |
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