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Bei Xiao, David Brainard; Surface material properties and color constancy of 3D objects. Journal of Vision 2009;9(8):359. doi: https://doi.org/10.1167/9.8.359.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Most previous research on color constancy has studied matte flat surfaces. Very little is known about color constancy for three-dimensional objects. Such objects can be made of different materials. We investigated the effect of object material properties on color constancy. Methods: Stimuli were computer-rendered three-dimensional scenes viewed stereoscopically. Three simulated scene illuminants were used: Neutral, Blue and Yellow. On each trial, a test sphere appeared briefly in the scene. On red/green trials, observes judged whether the test sphere appeared reddish or greenish. On blue/yellow trials, observers judged whether the test sphere appeared bluish or yellowish. A staircase procedure controlled the body color of the test sphere, and over trials this converged so that the sphere appeared achromatic. In different blocks, the specular component of the test sphere was varied to simulate different materials. The achromatic chromaticities for each material were compared across simulated illuminant changes to compute a constancy index (CI). Results: We ran consistent-cue and reduced-cue conditions. In the consistent-cue condition only the illuminant was varied, while the contextual surfaces in the scene remained fixed. The CIs were similar for all materials. It is possible that constancy was near ceiling for all materials, thus masking an effect of material. In the reduced-cue condition, we co-varied the simulated reflectance of the background wall with the illuminant, so as to hold the light reflected from the wall constant. This eliminated local contrast as a cue to the illuminant change. For data from the three observers studied so far, CIs were still similar for all materials, although with a trend in the direction of more constancy for glossy tests. Conclusion: Constancy is robust across changes in object material properties. Specular highlights on the test object may lead to an increase of constancy, but this effect is small if it is real.
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