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L. RaShae Jennings, J. Farley Norman, Jessica M. Swindle, Elizabeth M. Mullins, Amanda M. Beers; Stereoscopic shape discrimination is invariant across random changes in size. Journal of Vision 2009;9(8):35. doi: 10.1167/9.8.35.
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© ARVO (1962-2015); The Authors (2016-present)
A single experiment evaluated human observers' ability to discriminate the shape of 3-dimensional solid objects that varied in size and orientation in depth. The object shapes were defined by binocular disparity, Lambertian shading, and texture. The object surfaces were smoothly curved and had naturalistic shapes, resembling those of water-smoothed rocks. On any given trial, two objects were presented that were either the same or completely different in terms of shape. When the “same” objects were presented, they differed in their orientation in depth by either 25, 45, or 65 degrees. The observers were required to judge whether any given pair of objects were the “same” or “different” in terms of shape. The size of the objects was also varied by amounts up to +/− 40 percent relative to the standard size. The observers' shape discrimination performance was strongly affected by the magnitude of the orientation changes in depth — thus, their performance was viewpoint dependent. In contrast, the observers' discrimination abilities were not affected by changes in the overall size of the objects. It appears that human observers can perceive the 3-D shape of objects in a manner that is independent of size.
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