Weintroduce and explore a color phenomenon which requires the prior perception of motion to produce a spread of color over a region defined by motion. Wecall this motion-induced spread of color dynamic color spreading. The perception of dynamic color spreading is yoked to the perception of apparent motion: As the ratings of perceived motion increase, the ratings of color spreading increase. The effect is most pronounced if the region defined by motion is near 1 0 of visual angle. As the luminance contrast between the region defined by motion and the surround changes, perceived saturation of color spreading changes while perceived hue remains roughly constant. Dynamic color spreading is sometimes, but not always, bounded by a subjective contour. We discuss these findings in terms of interactions between color and motion pathways.Neon color spreading (see, e.g., van Tuijl, 1975;Varin, 1971) shows that the colors we perceive do not always match predictions based on the spectral content of the stimulus. In instances of neon color spreading, color is seen over regions which in isolation would appear achromatic. Specific geometric, color, and brightness features are required in order to induce the neon color spreading into nearby areas. Consider the example in Figure 1: A full green disk can be seen, although only eight radial lines, part green and part red, are drawn. Another feature of the colored disk is that it appears luminous-hence the label "neon" color spreading.In this paper we introduce and explore a phenomenon of color spreading which differs from standard neon color spreading in that it requires the prior perception ofmotion to produce a spread of color over a region defined by motion. We call this motion-induced color spreading dynamic color spreading for short. Two frames from a typical display of dynamic color spreading are shown in Figure 2. Each frame consists of a white square containing 900 dots placed randomly (sampled from a uniform distribution) within the square area. The dots do not move from one frame to the next; only their colors are updated as follows: All dots are colored red except for those within a (virtual) disk, which are colored green. The center ofthe disk translates from one frame to the next, with the consequence that some red dots in one frame are green in the next, and vice versa. Again, the physical placement of dots remains unchanged from frame to frame; only the colors of a small number of dots (those at the leading and trailing edges of the virtual disk) change from one frame to the next. TheWe thank M. Albert, B. Bennett, M. Braunstein, 1. Yellott, and two anonymous reviewers for helpful comments. This research was supported by ONR Contract NOOOI4-88-K-0354 (D.D,H.), NSF Grant BNS8819874 (CM.C.), andNEI Grant IROIEY08200 (CM.C.). Correspondence should be addressed to C M. Cicerone, Department of Cognitive Sciences, University of California, Irvine, Irvine, CA 92717 (e-mail: cciceron@uci.edu), Mathematica (Version 2.03) program used for generating such frames is given in App...
Abstract. Monocular observers perceive as three-dimensional (3D) many displays that depict three points rotating rigidly in space but rotating about an axis that is itself tumbling. No theory of structure from motion currently available can account for this ability. We propose a formal theory for this ability based on the constraint of Poinsot motion, i.e., rigid motion with constant angular momentum. In particular, we prove that three (or more) views of three (or more) points are sufficient to decide if the motion of the points conserves angular momentum and, if it does, to compute a unique 3D interpretation. Our proof relies on an upper semicontinuity theorem for finite morphisms of algebraic varieties. We discuss some psychophysical implications of the theory.
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