Abstract not found

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 this investigation of monocular perception of egocentric distance, the authors advocate the necessity of a perception-action approach because calibration is intrinsic to definite distance perception. A helmet-mounted camera and display were used to isolate optic flow generated by participants ' head movements toward a target, and participants ' reaches to place a stylus either in a target hole (Experiments 1, 2, and 4) or aligned under a target surface (Experiment 3) were analyzed. Conclusions are that binocular distance perception is accurate, monocular distance perception yields compression that is not eliminated by feedback, but feedback is used to eliminate underestimation generated by restriction of the size of the visual field. The study of definite distance perception requires a perception-action approach. As we argue, the reason is twofold. First, definite distance perception entails calibration and, therefore, a task-specific action that provides both feedback and a standard of accuracy. Calibration is complete once measurements are within a task-specific tolerance. The tolerance is determined by error variability and task requirements,

object distance during self-motion

Abstract-Three experiments providing a two-object display with monocular movement parallax acting as the only effective cue to depth were carried out with ten observers. The matched width of the variable (rear) object, i.e. the amount of constancy, was taken as a measure of the effectiveness of movement parallax under the condition under question. Experiment I showed that successively disparate images (position parallax) are not sufficient to produce the impression of depth as compared to movement parallax. In Experiment 2 and 3 velocity (1%) and amount (d) of head movement were varied. At values 5-10 times threshold, depth perception by movement parallax reached half of its maximal effectiveness, It was virtually independent of L ‘ and d when these values exceeded 20 times threshold level. Kq wortfs-movement parallax; monocular depth perception Although monocular movement parallax has been investigated intermittently since Bourdon’s experiment (1898), there still exist studies questioning its role as a cue to depth. Observers perceived motion rather

How the eye measures reality and virtual reality We, as a species, seem to have been fascinated with pictures throughout our history. The paintings at Niaux, Altamira, and Lascaux (Clottes, 1995; Ruspoli, 1986), for example, are known to be about 14,000 years old, but with the recently discovered paintings in the Grotte Chauvet, the origin of representational art appears to have been pushed back even further (Chauvet, Brunel Deschamps, & Hillaire, 1995; Clottes, 1996), to 20,000 years ago if not longer. 1 Thus, these paintings date from about the time at which homo sapiens sapiens first appeared in Europe (Nougier, 1969). We should remember these paintings in the context of virtual reality; our fascination with pictures is by no means recent. My intent is threefold: first, to discuss our perception of the cluttered layout, or space, that we normally find around us; second, to discuss the development of representational art up to our current appreciation of it; and third, to apply this knowledge to virtual reality systems. The first discussion focuses on the use of multiple sources of information specifying ordinal depth relations, within the theoretical framework that I have called directed perception

The onset of locomotion heralds one of the major life transitions in early development and involves a pervasive set of changes in perception, spatial cognition, and social and emotional development. Through a synthesis of published and hitherto unpublished findings, gathered from a number of converging research designs and methods, this article provides a comprehensive review and reanalysis of the consequences of self-produced locomotor experience. Specifically, we focus on the role of locomotor experience in changes in social and emotional development, referential gestural communication, wariness of heights, the perception of self-motion, distance perception, spatial search, and spatial coding strategies. Our analysis reveals new insights into the Supplementary materials to this article are available on the World Wide Web at

Monocular perception of egocentric distance via optic flow generated by head movement toward a target was investigated with a helmet-mounted video camera and display. Ability to perceive target distance was assessed with 2 response measures: verbal reports and reaches. Systematic and random errors differed as a function of the response measure. Verbal estimates of targets within and beyond reach were obtained before and after the performance of reaches to targets within reach. Systematic errors of verbal estimates changed but did not decrease overall. Random error decreased. Verbal estimates and reaches were performed concurrently to targets within reach. Verbal and reaching errors were uncorrelated. Verbal judgments appear to have been anchored using the range of distances experienced while reaching rather than being calibrated to the perceptual information itself. Discussion focuses on the advantages of action response measures. Reaching to bring the hand to a specific location in space is a usual component of everyday manual activities, such as reaching for a doorknob or a cup. The accurate execution of such activity requires information about both target distance and direction. We present research investigating the possibility that information about distance is revealed in optic flow generated by voluntary head motion. This possibility is underscored by several studies that confirm that reaching is more accurate when the head is free to move (Biguer,

Abstract-Using the head motion procedure, the apparent distance of a point of light in an otherwise dark visual field was measured under conditions in which oculomotor cues (accommodation, convergence) and absolute motion parallax were varied together and separately. It was concluded that absolute motion parallax is almost as effective a cue to distance as are oculomotor cues from monocular observation, but is not as effective as oculomotor cues from binocular observation. Evidence was also presented that the null adjustment method, used in conjunction with the head motion procedure, provides an unbiased measure of apparent distance. In a series of articles (Gogel, 1976, 1977; Gogel and Newton, 1976; Gogel and Tietz, 1973, 1974, 1977) a new method of measuring apparent distance called the head motion procedure has been described and applied to the measurement of perceived distance from several distance cues. With the head motion procedure, the head is moved in a frontoparallel plane and judgments are obtained of the apparent motion