Abstract not found

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

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

Previous work [Prince, S. J. D, & Eagle, R. A. (1999). Size-disparity correlation in human binocular depth perception. Proceedings of the Royal Society: Biological Sciences, 266, 1361 -- 1365] has demonstrated that disparity sign discrimination performance in isolated bandpass patterns is supported at disparities much larger than a phase disparity model might predict. One possibility is that this extended performance relies on a separate second-order system [Hess, R. F., & Wilcox, L. M. (1994). Linear and non-linear filtering in stereopsis. Vision Research, 34, 2431 -- 2438]. Here, a `weighted directional energy' model is developed which explains a large body of crossed versus uncrossed disparity discrimination data with a single mechanism. This model assumes a population of binocular complex cells at every image point with a range of position disparity shifts. These cells sample a local energy function which is weighted so that energy at large disparities is relatively attenuated. Disparity sign is determined by summing and comparing energy at crossed and uncrossed disparities in the presence of noise. The model qualitatively predicts matching data for one-dimensional Gabor stimuli. This scheme also predicts DMax in Gabor stimuli and filtered noise. Moreover, a range of `non-linear' phenomena, in which disparity is perceived from contrast envelope information alone, can be explained. The weighted directional energy model presents a biologically plausible, parsimonious explanation of matching behaviour in bandpass stimuli for both `first-order' and `second-order' stimuli which obviates the need for multiple mechanisms in stereo correspondence. 2000 Elsevier Science Ltd. All rights reserved.

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

Binocular disparity is the input to stereopsis, which is a very strong depth cue in humans. However, the distribution of binocular disparities in natural environments has not been quantitatively measured. In this study, we converted distances from accurate range maps of forest scenes and indoor scenes into the disparities that an observer would encounter, given an eye model and fixation distances (which we measured for the forest environment, and simulated for the indoor environment). We found that the distributions of natural disparities in these two kinds of scenes are centered at zero, have high peaks, and span about 5 deg, which closely matches the macaque MT cells ’ disparity tuning range. These ranges are fully within the operational range of human stereopsis determined psychophysically. Suprathreshold disparities (910 arcsec) are common rather than exceptional. There is a prevailing notion that stereopsis only operates within a few meters, but our finding suggests that we should rethink the role of stereopsis at far viewing distances because of the abundance of suprathreshold disparities. Keywords: stereopsis, binocular disparity, stereoacuity, stereo upper limit, Panum’s fusion area Citation: Liu, Y., Bovik, A. C., & Cormack, L. K. (2008). Disparity statistics in natural scenes. Journal of Vision, 8(11):19, 1–14,

THE PROBLEM with which this study is concerned is the relationship between binocular fusion and simultaneity of stimulation of the two eyes. This relationship has considerable theoretical importance. For example, it is typically assumed that simultaneity of arrival of discharges at the cortex from the two retinas is a necessary condition for stereopsis. Also,