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Katja Doerschner, Laurence T. Maloney; Lightness perception in scenes with motion-based shading cues to the spatial distribution of illumination. Journal of Vision 2006;6(6):711. doi: 10.1167/6.6.711.
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© ARVO (1962-2015); The Authors (2016-present)
When a gray matte surface changes its orientation with respect to a collimated light source the intensity of the light reflected from this surface changes, varying with the angle between surface normal and light source direction. The luminance changes of the rotating patch are a cue to the spatial distribution of the illumination. We examine whether observers use this motion-based shading cue in estimating the albedo of a static test surface under the same illumination.
Methods: Six observers viewed computer-rendered 3D scenes, each consisting of an array of smoothly rotating (100° partial rotation) matte rectangles of the same albedo. A punctate light source placed slightly above and far behind the observer illuminated the scenes. Observers adjusted the luminance of a static central test patch until its perceived albedo matched that of the rotating rectangles. On some trials, observers judged the albedo of the test patch at orientations that never occurred in the animated sequences (to preclude simple copying of the luminance of a rotating patch at the same orientation). In a second condition specular spheres were added to the scene to serve as additional cue to the properties of the illumination.
Results: Observers partially discounted the spatial distribution of the light in estimating surface albedo of the static test patch, successfully utilizing the motion-based shading cue. But only when specular spheres were also present did observers' luminance settings approach veridical, suggesting that motion-induced shading is a relatively weak cue to the spatial distribution of the illuminant.
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