Browsing by Subject "Depth perception"
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Item Evolved navigation theory and the environmental vertical illusion(2007) Jackson, Russell Eric; Cormack, Lawrence K.Item Evolved navigation theory and the environmental vertical illusion(2007-05) Jackson, Russell Eric, 1978-; Cormack, Lawrence K.These studies suggested that everyday visual perception is unconsciously subject to large-scale illusions on ubiquitous environmental surfaces. Participants overestimated environmentally vertical surfaces and did so to an increasing degree with longer surfaces, neither of which occurred with environmentally horizontal surfaces. I title this illusion the environmental vertical illusion. The severity of previous injury from a fall related to the degree of illusion such that more severe previous falling injuries were associated with lower illusion magnitudes, even though the illusion is still present at higher injury severities. I predicted these data from hypotheses derived from Evolved Navigation Theory (ENT), which focuses on how navigational costs over evolutionary time can shape cognitive and perceptual mechanisms. Virtual reality data suggested that unrealistically artificial falling costs failed to produce the environmental vertical illusion, even on apparently vertical surfaces. Virtual reality methods also suggested that distance estimation from immobile visual displays deviated from natural distance estimation in important ways that hold implications for tasks involved in piloting and surgery. Data from physical and virtual reality suggested that no clear relationship existed between the 2D Vertical-Horizontal Illusion and 3D distance estimates gathered here. The current findings hold implications outlined under ENT for areas such as anxiety disorders, piloting, surgery, individual differences, and visual stimuli design. However, these findings may be most important because distance and orientation perception occurs constantly in most visual systems and, consequently, most behaviors. Understanding how distance perception occurs thus helps us to understand one of the most common of all psychological experiences. These data suggest that a primary component of human visual experience is illusory. However, through the use of a theory rooted in evolution (ENT), we may be able to predict and better understand these important features of human psychology.Item Naturalistic depth perception(2015-05) McCann, Brian Clark; Geisler, Wilson S.; Hayhoe, Mary; Huk, Alex; Cormack, Larry; Bovik, AlMaking inferences about the 3-dimensional spatial structure of natural scenes is a critical visual function. While spatial discrimination both in depth and on the image plane has been well characterized for simple stimuli, little is known about our ability to discriminate depth in natural scenes, particularly at far distances. To begin filling in this gap we: (i) developed a database of 80 stereoscopic images paired with the corresponding measured distance information, (ii) used these scenes as psychophysical stimuli and measured near-far discrimination acuity in 4 observers as a function of distance and the visual angle separating the targets, (iii) made additional measurements under patched-eye (monocular) viewing conditions to evaluate the importance of binocular vision in depth discrimination as a function of viewing geometries. We find that binocular thresholds are roughly a constant Weber fraction of the distance for absolute distances ranging from 4 to 28 meters. Further, measured thresholds were around 1% for small separations, and increased to 4% for stimuli separated by 10 deg. Thus, the ability to discriminate depth in natural scenes is very good out to considerable distances. To investigate the basis of this discrimination ability, monocular thresholds were measured. We found that monocular thresholds were elevated for distances less than 15 meters, but were comparable to binocular thresholds for greater distances. Accurate depth perception depends on combining (fusing) multiple sources of sensory information. Thus binocular thresholds probably involve fusing separate monocular and disparity-derived estimates. Under the assumption of Gaussian distributed independent estimates, Bayes rule provides a simple reliability-weighted summation model of cue combination. Using disparity threshold measurements by Blakemore (1970), and the current monocular thresholds, parameter-free predictions were generated for the current binocular thresholds. These predictions were in broad agreement with the data, suggesting that the disparity and monocular cues are separable and combined optimally in natural scenes.Item The Comparison of Yellow and Clear Faceplates in Facilitating Accurate Distance Perception in an Underwater Environment(Texas Tech University, 1980-12) Reichenbach, John HarrisonNot Available.Item The effects of display format and visual enhancement cues on performance of three-dimensional teleoperational tasks(Texas Tech University, 1998-05) Park, Sung HaDepth perception (as a third dimension) on a two-dimensional surface of a display interface very much determines the quality of the teleoperation system. In this research, among various teleoperation sensing requirements, the television depth requirement was investigated in detail. This research was intended to extend our understanding of the effects of visual display formats and visual enhancement cues on the ability of human operators to effectively control robot manipulators in three-dimensions. Visual display formats and visual enhancement cues were evaluated by employing a pick-and-place (picking up a virtual object and placing it into a storage rack) task in a simulated teleorobotic task environment. Three different display formats, a multiple 2-dimensional (2-D) display, a 3-dimensional (3-D) perspective display, and a 3-D stereoscopic display were simulated using a combination of various programming tools (external motif, C language, and TELEGRIP software) on a SiliconGraphics Indigo2 workstation. In order to aid human operators in perceiving depth, four different visual enhancement depth cues (including no enhancement cue) were also proposed and incorporated into each display format. Task difficulties were generated by manipulating the size of the storage rack. To compare different display formats and visual enhancement cues, various teleoperation performance measures were collected under each display condition. The measures included the time-to-completion, accuracy, subjective ratings of workload, and distance (move by the end effector). The results showed that the multiple 2-D display was superior to the perspective and stereoscopic displays, if no visual enhancement cues were provided. If provided with two of the proposed visual enhancement cues, the translucent reference cylinder and four reference lines, the stereoscopic and perspective displays were equivalent to the multiple 2-D display. The traditional single reference line was not sufficient to provide appropriate depth information on the stereoscopic and perspective displays. The stereoscopic display resulted in better performance than the perspective display only under the high task difficulty condition.