Various visual cues provide information about depth and shape in a scene. When several of these cues are simultaneously available in a single location in the scene, the visual system attempts to combine them. In this paper, we discuss three key issues relevant to the experimental analysis of depth cue combination in human vision: cue promotion, dynamic weighting of cues, and robustness of cue combination. We review recent psychophysical studies of human depth cue combination in light of these issues. We organize the discussion and review as the development of a model of the depth cue combination process termed modified weak fusion (MWF). We relate the MWF framework to Bayesian theories of cue combination. We argue that the MWF model is consistent with previous experimental results and is a parsimonious summary of these results. While the MWF model is motivated by normative considerations, it is primarily intended to guide experimental analysis of depth cue combination in human vision. We describe experimental methods, analogous to perturbation analysis, that permit us to analyze depth cue combination in novel ways. In particular these methods allow us to investigate the key issues we have raised. We summarize recent experimental tests of the MWF framework that use these methods. Depth Multiple cues Sensor fusion

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this article we focus on the seemingly contradictory results of two quite different approaches to the problem, one dealing with the properties of visually perceived space and the other with visually directed action

Distance judgments are difficult in current virtual environments, limiting their effectiveness in conveying spatial information. This problem is apparent when contact occurs while a user is manipulating objects. In particular, the computer graphics used to support current generation immersive interfaces does a poor job of providing the visual cues necessary to perceive when contact between objects is about to occur. This perception of imminent contact is important in human motor control. Its absence prevents a sense of naturalness in interactive displays which allow for object manipulation. This paper reports results from an experiment evaluating the effectiveness of binocular disparity, cast shadows, and diffuse interreflections in signaling imminent contact in a manipulation task.

this article should be addressed to either Sergio S. Fukusima, Department of Psychology, FFCLRP, University of Sat Paulo, Ribeiro Preto, Sat Paulo, Brazil, CEP 14050-901, or Jack M. Loomis, Department of Psychology, University of California, Santa Barbara, California 93106-9660. Electronic mail may be sent via Intemet to fukusima@usp.br or loomis @ psych.ucsb.edu. distance is not linked tightly to that of exocentric distance (see also Gogel, 1977), our focus here is on the former. It generally is accepted that when visual cues to distance are reduced greatly, egocentric distance is misperceived (e.g., Baird, 1970; Da Silva, 1985: Foley, 1977, 1980; Foley & Held, 1972; Gogel, 1974; Holway & Boring, 1941; Kiinnapas, 1968; Philbeck & Loomis, 1997; Sedgwick, 1986). Under "full-cue" conditions, in which a stimulus-rich envi- ronment is viewed under good illumination, however, there is little agreement about whether perception is accurate, mainly because of the diversity of findings stemming from different experimental methods. With respect to egocentric distance, much of the research conducted under full-cue conditions suggests that perceived distance is nearly linear in physical distance and appropriately scaled, at least for targets within 20 m (e.g., verbal reports, Da Silva, 1985; Sedgwick, t986; Teghtsoonian & Teghtsoonian, 1969, t970; blind walking to previewed targets, Corlett, Patla, & Williams, 1985; Elliott, 1986, 1987: Elliott, Jones, & Gray, 1990; Loomis, Da Silva, Fujita, & Fukusima, 1992; Rieser, Ashmead, Talor, & Youngquist, 1990; Steenhuis & Goodale, 1988; Thomson, 1983); in those studies, power functions with exponents close to 1.0 were obtained. The results of other research under the same viewing conditions and over the' same physical distances suggest a c...

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

Can distance perception be studied using virtual reality (VR) if distances are systematically underestimated in VR head-mounted displays (HMDs)? In an experiment in which a real environment was observed through an HMD, via live video, distances, as measured by visually directed walking, were underestimated even when the perceived environment was known to be real and present. However, the underestimation was linear, which means that higher-order space perception effects might be preserved in VR. This is illustrated in a second experiment, in which the visual horizon was artificially manipulated in a simulated outdoor field presented in immersive VR. As predicted by the claim that angle of declination from the horizon may serve as a strong cue to distance, lowering the horizon line produced “expansive ” judgments of distance (power function exponents greater than one) both in verbal and in motor estimates.

Unconstrained point-to-point human arm movements are generally gently curved, a fact which has been used to assess the validity of models of trajectory formation. In this study we examined the relationship between curvature perception and movement curvature for planar sagittal and transverse arm movements. We found a significant correlation (p ! 0:0001, n = 16) between the curvature perceived as straight and the curvature of actual arm movements. We suggest that subjects try to make straight-line movements, but that actual movements are curved because visual perceptual distortion makes the movements appear to be straighter than they really are. We conclude that perceptual distortion of curvature contributes to the curvature seen in human point-to-point arm movements and that this must be taken into account in the assessment of models of trajectory formation. Introduction There are several invariant features of point-to-point human arm movements: trajectories 1 tend to be gently curv...

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

The geometry of binocular projection is analyzed in relation to the primate visual system. An oculomotor parameterization that includes the classical vergence and version angles is defined. It is shown that the epipolar geometry of the system is constrained by binocular coordination of the eyes. A local model of the scene is adopted in which depth is measured relative to a plane containing the fixation point. These constructions lead to an explicit parameterization of the binocular disparity field involving the gaze angles as well as the scene structure. The representation of visual direction and depth is discussed with reference to the relevant psychophysical and neurophysiological literature. © 2008 Optical Society of America OCIS codes: 330.1400, 330.2210. 1.