Abstract-Random dot techniques were used to investigate the human visual system’s sensitivity to sinusoidal depth modulations specified by motion parallax information. Thresholds for perceiving depth were found to be smallest when the spatial frequency of the depth corrugations was between 0.2 and 0.5 c/deg visual angle. These data were compared with the equivalent thresholds for perceiving depth corrugations specified by binocular disparity using similar apparatus and psychophysical procedures. The similarity between the sensitivity functions is suggestive of a closer relationship between the two systems than has previously been thought.

The results of three experiments demonstrated that the visual system calibrates motion parallax according to absolute-distance information in processing depth. The parallax was created by yoking the relative movement of random dots displayed on a cathode-ray tube to the movements of the head. In Experiment l, at viewing distances of 40 cm and 80 cm, observers reported the apparent depth produced by motion parallax equivalent to a binocular disparity of 0.47". The mean apparent depth

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

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The accuracy of depth judgments that are based on binocular disparity or structure from motion (motion parallax and object rotation) was studied in 3 experiments. In Experiment 1, depth judgments were recorded for computer simulations of cones specified by binocular disparity, motion parallax, or stereokinesis. In Experiment 2, judgments were recorded for real cones in a structured environment, with depth information from binocular disparity, motion parallax, or object rotation about the y-axis. In both of these experiments, judgments from binocular disparity information were quite accurate, but judgments on the basis of geometrically equivalent or more robust motion information reflected poor recovery of quantitative depth information. A 3rd experiment demonstrated stereoscopic depth constancy for distances of 1 to 3 m using real objects in a well-illuminated, structured viewing environment in which monocular depth cues (e.g., shading) were minimized. It has been pointed out that the geometric information supporting the perception of depth from binocular disparity is actually less determinate than that supporting the recovery of structure from object rotation or motion parallax

In three experiments, we investigated the integration of three-dimensional information provided over time by different depth cues. In the first experiment, we found that the perceptual derivation of surface orientation from the optic flow was affected by the prior presentation of static stereo information in the same spatial location. This bias weakened as the length of the motion sequence increased, but it was still present after 800 msec. In the second experiment, conversely, we found that the perceived orientation of a stereo-specified surface was not influenced by the prior presentation of a static stereo surface. In a third experiment, we found that two surfaces defined by identical disparity fields did not elicit the same perceived depth if, previously, one of them had been specified by a conjunction of stereo and motion information. This effect was found to last for at least 400 msec. Taken together, these findings indicate that interactions exist among different sources of depth information, even when they are provided at different moments of time. Human observers obtain information about threedimensional (3-D) shape from a large number of depth cues provided by the visual environment. In recent years, many studies have been carried out to investigate the

There are a variety of stereoscopic after-effects in which exposure to a stimulus with a particular slant or curvature affects the perceived slant or curvature of a subsequently presented stimulus. These after-effects have been explained as a consequence of fatigue (a decrease in responsiveness) among neural mechanisms that are tuned to particular disparities or patterns of disparity. In fact, a given disparity pattern is consistent with numerous slants or curvatures; to determine slant or curvature, the visual system must take the viewing distance into account. We took advantage of this property to examine whether the mechanisms underlying the stereoscopic curvature after-effect are tuned to particular disparity patterns or to some other property such as surface curvature. The results clearly support the second hypothesis. Thus, 3D after-effects appear to be caused by adaptation among mechanisms specifying surface shape rather than among mechanisms signaling the disparity pattern. © 2001 Elsevier

Abstract not found

Motion as a fundamental visual dimension Functional aspects of image motion processing (I) Encoding of the third dimension (2) Time to collision (TTC) (3) Image segmentation (4) Motion as a proprioceptive sense (5) Motion as a stimulus to drive eye movements (6) Motion as required for pattern vision (7) Image motion processing as useful for perceiving real moving objects Multiplicity of functional roles Motion blindness? Parallel and serial processing within an early motion system: a skeletal model Random dot stimuli D ImAX Dm, Intermediate values of velocity Experiments using sinusoidal gratings Common space-time framework to account for random dot and grating data Motion hyperacuity Metrical encoding of velocity Fourier domain description of moving images Chromatic input to the motion system? Computational theories of motion processing Early models Recent models Beyond the simple pair? Single cell analysis of image motion Definitional issues Movement, nonmovement and pre-movement units Motion processing at the extrastriate level Orientation tuning in the motion system An oblique effect for motion? The aperture problem Temporal integration of velocity signals Higher-order computations on the optical flow field Derivatives of velocity Interocular comparison of motion signals: motion in depth