A global shape judgement task was used to investigate the combination of stereopsis and kinetic depth. With botb cues present, there were no distortions of shape perception, even under conditions where either cue alone did show such distortions. We suggest that the addition of motion information overcomes the stereo distance scaling problem. However, when incongruent combinations of disparity and motion were used, the results did not match predictions of a number of combination theories. These data could be described by a model which used weighted linear combination afier correctly scaling disparities for viewing distance. When the motion cue was weakened by presenting only two frames of each motion sequence, stereo was weighted more heavily. Stereopsis Structure-from-motion Three-dimensional shape perception Integration of depth cues

A computational explanation of the illusory movement experienced upon extended viewing of Enigma, a static figure painted by Leviant, is presented. The explanation relies on a model for the interpretation of three-dimensional motion information contained in retinal motion measurements. This model shows that the Enigma figure is a special case of a larger class of figures exhibiting the same illusory movement and these figures are introduced here. Our explanation supports the view that higher-level processes are the cause of these illusions [29] and suggests a number of new experiments to unravel the functional structure of the motion pathway.

Geometric considerations suggest that the problem of estimating a system's three-dimensional (3D) motion from a sequence of images, which has puzzled researchers in the fields of Computational Vision and Robotics as well as the Biological Sciences, can be addressed as a pattern recognition problem. Information for constructing the relevant patterns is found in spatial arrangements or gratings, that is, aggregations of orientations along which retinal motion information is estimated. The exact form of the gratings is defined by the shape of the retina or imaging surface; for a planar retina they are radial lines, concentric circles, as well as elliptic and hyperbolic curves, while for a spherical retina they become longitudinal and latitudinal circles for various axes. Considering retinal motion information computed normal to these gratings, patterns are found that have encoded in their shape and location on the retina subsets of the 3D motion parameters. The importance of these pattern...

Convergent evidence for the visual analysis of optic flow through anisotropic attenuation of high spatial frequencies