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Journal of Vision (2004) 4, 798-820 http://journalofvision.org/4/9/10/ 798 Specular reflections and the perception of shape

Summary: Journal of Vision (2004) 4, 798-820 http://journalofvision.org/4/9/10/ 798
Specular reflections and the perception of shape
Many materials, including leaves, water, plastic, and chrome exhibit specular reflections. It seems reasonable that the
visual system can somehow exploit specular reflections to recover three-dimensional (3D) shape. Previous studies (e.g.,
J. T. Todd & E. Mingolla, 1983; J. F. Norman, J. T. Todd, & G. A. Orban, 2004) have shown that specular reflections aid
shape estimation, but the relevant image information has not yet been isolated. Here we explain how specular reflections
can provide reliable and accurate constraints on 3D shape. We argue that the visual system can treat specularities
somewhat like textures, by using the systematic patterns of distortion across the image of a specular surface to recover
3D shape. However, there is a crucial difference between textures and specularities: In the case of textures, the image
compressions depend on the first derivative of the surface depth (i.e., surface orientation), whereas in the case of
specularities, the image compressions depend on the second derivative (i.e., surfaces curvatures). We suggest that this
difference provides a cue that can help the visual system distinguish between textures and specularities, even when
present simultaneously. More importantly, we show that the dependency of specular distortions on the second derivative
of the surface leads to distinctive fields of image orientation as the reflected world is warped across the surface. We find
that these "orientation fields" are (i) diagnostic of 3D shape, (ii) remain surprisingly stable when the world reflected in the
surface is changed, and (iii) can be extracted from the image by populations of simple oriented filters. Thus the use of
specular reflections for 3D shape perception is both easier and more reliable than previous computational work would
Keywords: 3D shape perception, specularity, shape-from-texture, shape-from-shading, gloss, natural image statistics, ma-
terial perception, modeling


Source: Adelson, Edward - Computer Science and Artificial Intelligence Laboratory, Department of Brain and Cognitive Science, Massachusetts Institute of Technology (MIT)


Collections: Biology and Medicine