Virtual environments are envisioned as being systems that will enhance the communication between humans and computers. If virtual systems are to be effective and well received by their users, considerable human-factors research needs to be accomplished. This paper provides an overview of many of these human-factors issues, including human performance efficiency in virtual worlds (which is likely influenced by task characteristics, user characteristics, human sensory and motor physiology, multimodal interaction, and the potential need for new design metaphors); health and safety issues (of which cybersickness and deleterious physiological aftereffects may pose the most concern); and the social impact of the technology. The challenges each of these factors present to the effective design of virtual environments and systematic approaches to the resolution of each of these issues are discussed.

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Human Factors Issues in Virtual Environments: A Review of the Literature

Head-worn display design is inherently an interdisciplinary subject fusing optical engineering, optical materials, optical coatings, electronics, manufacturing techniques, user interface design, computer science, human perception, and physiology for assessing these displays. This paper summarizes the state-of-the-art in head-worn display design (HWD) and development. This review is focused on the optical engineering aspects, divided into different sections to explore principles and applications. Building on the guiding fundamentals of optical design and engineering, the principles section includes a summary of microdisplay or laser sources, the Lagrange invariant for understanding the trade-offs in optical design of HWDs, modes of image presentation (i.e., monocular, biocular, and stereo) and operational modes such as optical and video see-through. A brief summary of the human visual system pertinent to the design of HWDs is provided. Two optical design forms, namely, pupil forming and non-pupil forming are discussed. We summarize the results from previous design work using aspheric, diffractive, or holographic elements to achieve compact and lightweight systems. The applications section is organized in terms of field of view requirements and presents a reasonable collection of past designs

Head-worn displays: a review

The ability to accurately estimate distance is an essential component of navigating large-scale spaces. Although the factors that influence distance estimation have been a topic of research in real-world environments for decades and are well known, research on distance estimation in virtual environments (VEs) has only just begun. Initial investigations of distance estimation in VEs suggest that observers are less accurate in estimating distance in VEs than in the real world (Lampton et al., 1995). Factors influencing distance estimates may be divided into those affecting perceived distance (visual cues only) and those affecting traversed distance to include visual, cognitive, and proprioceptive cues. To assess the contribution of the various distance cues in VEs, two experiments were conducted. The first required a static observer to estimate the distance to a cylinder placed at various points along a 130-foot hallway. This experiment examined the effects of floor texture, floor pattern, and object size on distance estimates in a VE. The second experiment required a moving observer to estimate route segment distances and total route distances along four routes, each totaling 1210 feet. This experiment assessed the effects of movement method, movement speed, compensatory cues, and wall texture density. Results indicate that observers underestimate distances both in VEs and in the real world, but the underestimates are more extreme in VEs. Texture did not reliably affect the distance estimates, providing no compensation for the gross underestimates of distance in VE. Traversing a distance improves the ability to estimate that distance, but more natural means of moving via a treadmill do not necessarily improve distance estimates over traditional methods of moving in VE (e.g., using a joystick). The addition of compensatory cues (tone every 10 feet traversed on alternate route segments) improves VE distance estimation to almost perfect performance.

Judging Perceived and Traversed Distance in Virtual Environments

This report represents a committee summary of the current state of knowledge regarding aftereffects and sense of presence in virtual environments (VEs). The work presented in this article, and the proposed research agenda, are the result of a special session that was set up in the framework of the Seventh International Conference on Human Computer Interaction Recommendations were made by the committee regarding research needs in after effects and sense of presence, and, where possible, priorities were suggested. The research needs were structured in terms of the short medium, and long term and, if followed, should lead toward the effective use of VE technology. The 2 most critical research issues identified were (a) standardization and use of measurement approaches for aftereffects and (b) identification and prioritization of sensorimotor discordances that drive after effects. Identification of aftereffects countermeasures (i.e., techniques to assist users in readily transitioning between the real and vir...

Aftereffects and sense of presence in virtual environments: formulation of a research and development agenda.

The volatile global security environment has changed warfighting. Battles in the arena of terrorism demand mature judgment, decision-making, and collaboration of warfighters who are often young, and often “part-time” (Reserve or National Guard) soldiers. Traditional methods of training are strained by logistical challenges, geographic distribution of personnel, and limited resources that preclude frequent field training. This situation is changing the way we train warfighters. Reaching high levels of skill requires novel approaches to training (DoD, 2004) to ensure that training resources are allocated in a cost-effective manner that optimizes skill acquisition and retention (Ricci, Salas, & Cannon-Bowers, 2002). There are two traditional approaches to training in the military. Classroom education provides valuable declarative knowledge to warfighters. Such education is often supplemented today by web-based distance learning courses, for which the Department of Defense has defined the current industry format standards (Advanced Distributed Learning, 2004). However, warfighters also need practice applying the complex skills they study, and practicing them to proficiency. This training is typically delivered in field exercises that expose warfighters to battle environments and stressors, and give them experience interacting in battle environments. However, exercises are expensive, logistically cumbersome, and often dangerous. Computer-based alternatives to live training have become more common in recent years. These alternatives are simulators, computer-based training systems, and video games. Simulators are systems that emulate visual stimuli and physical controls from the operational environment (Bonk & Dennen, 2005), common examples being flight and driving simulators. Computer-based training systems, sometimes referred to as “lightweight simulations,” are web- or PC-based systems designed to provide individual instruction on specific mission skills. These systems represent the physical and behavioral characteristics of military systems with very high fidelity. PC flight simulators such as AirBook

From Gaming to Training: A Review of Studies on Fidelity, Immersion, Presence, and Buy-in and Their Effects on Transfer in PC-Based Simulations and Games

The utilization of head-mounted displays (HMDs) in hign-end applications such as medical, engineering, and scientific visualization necessitates that the position of objects be rendered accurately and precisely. Accuracy and precision of rendered depth for near-field visualization were measured in a custom-designed bench prototype HMD. Experimental results were compared to theoretical predictions established from a computational model for rendering and presenting virtual images by Robinett and Rolland (1992). Such a theoretical model provided the necessary graphics transformations required so that rendered virtual objects be perceived at the rendered depth in binocular HMDs. Three object shades of various sizes were investigated under two methodologies: tne method of constant stimuli modified for random size presentation and the method of adjustments. Results snow a 2 mm and an 8 mm performance for the accuracy and the precision of rendered depth in HMDs, respectively. Results of the assessment of rendered depth in HMDs for near-field visualization support employing the method of adjustments over the method of constant stimuli whether or not the method of constant stimuli is modified for random size presentation.

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Method of adjustments versus method of constant stimuli in the quantification of accuracy and precision of rendered depth in head-mounted displays

This paper provides an overview of the literature on the visual system, placing special emphasis on those visual characteristics regarded as necessary to produce adequate visual fidelity in virtual environments. These visual cues apply to the creation of various virtual environments including those involving flying, driving, sailing, or walking. A variety of cues are examined, in particular, motion, color, stereopsis, pictorial and secondary cues, physiological cues, texture, vertical development, luminance, field-of-view, and spatial resolution. Conclusions and recommendations for research are also presented.

Characteristics of visual fidelity in the virtual environment

This research examined perceptual and cognitive functioning as a function of age. The results obtained are presented in this report. These results are now being analyzed and in a future report will be related to recommendations for training, rehabilitation, and automotive design, as well as assessment.

Cognitive and perceptual factors in aging and driving performance

Rather than researchers having to rely on manufacturers' specifications or an optical or engineering analysis, this paper provides a psychophysical method for determining the horizontal and vertical field of view of an HMD system. The technique employed makes use of a strobe light induced afterimage of two lights that subtend a predetermined size. This after image can then be used to set the width of two bars in the virtual environment and the number of pixels between the bars can be determined. Simple equations are provided to allow a determination of the basic dimensions of the display.

Determining the field of view in hmds: A psychophysical method

The main objective of this research was to investigate the effects of foveal load on sensitivity in the peripheral visual field. The first experiment was presented at previous meeting of the Human Factors Society. Here, foveal load was manipulated by comparing the fixation of a cross vs. a simple first-order compensatory tracking task display. Peripheral sensitivity was determined simultaneously for light flashes presented at different eccentricities along the horizontal meridian. In general, the results showed no losses in peripheral sensitivity or a “tunnel vision” effect under the experimental conditions employed. Three more experiments have been carried out since that presentation. More complex tracking tasks have been employed in order to vary foveal load and the difficulty of the perimetry task has also been manipulated in one experiment by including lights on the vertical meridian. Whether or not a loss or a gain in peripheral sensitivity depends upon the complexity of the foveal task and to some e...

Edward J. Rinalducci

Papers

Method of adjustments versus method of constant stimuli in the quantification of accuracy and precision of rendered depth in head-mounted displays

Characteristics of visual fidelity in the virtual environment

Cognitive and perceptual factors in aging and driving performance

Determining the field of view in hmds: A psychophysical method

Further Experiments on the Effects of Foveal Load on Peripheral Vision