Cite as:
Boyaci H, Maloney L T, 2001, "Effect of complexity and ordinal transformations of luminance on binocular shape perception" Perception 30 ECVP Abstract Supplement

Effect of complexity and ordinal transformations of luminance on binocular shape perception

H Boyaci, L T Maloney

Several studies in literature suggest hints of better shape estimations in complex scenes. We are testing the effects of scene complexity and ordinal transformations of luminance on shape perception. An observer judged the surface normal of computer-rendered ellipsoids at preset locations in four scenes with varying complexity, where complexity is defined by the number of ellipsoids present, and with two ordinal transformations which were power functions of intensity -- one compressive, one expansive. Stimuli were rendered stereo image pairs presented in a computer-controlled Wheatstone stereoscope. All ellipsoids had the same colour and surface reflectance function, which is Lambertian + specular (specularity 0.001). Observer completed 400 trials by adjusting a monocular gradient probe to estimate the surface normal at preset locations with 10 repetitions for each. One observer completed the task. In the range of ordinal transformations and complexities employed, we find no discernible effect. Under certain conditions, however, such as an additional ellipsoid casting shadow on target, observer's judgment is substantially influenced around such a shadow boundary. Our findings suggest that human shape algorithm uses only ordering of luminance values in binocular shape-from-shading/contour/specularity and that a single ellipsoid is complex enough to permit stable reconstruction.

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