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Thomas Crea

Bio: Thomas Crea is an academic researcher from University of Virginia. The author has contributed to research in topics: Literature survey & Simulator sickness. The author has an hindex of 2, co-authored 2 publications receiving 273 citations.

Papers
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Journal ArticleDOI
TL;DR: This paper focuses on research that produces specific, measured results that apply to VE research, and focuses on military literature that may be hard for traditional academics to locate via the standard journals.
Abstract: Researchers in the field of virtual environments VE, or virtual reality, surround a participant with synthetic stimuli, The flight simulator community, primarily in the U.S. military, has a great deal of experience with aircraft simulations, and VE researchers should be aware of the major results in this field. In this survey of the literature, we have especially focused on military literature that may be hard for traditional academics to locate via the standard journals. One of the authors of this paper is a military helicopter pilot himself, which was quite useful in obtaining access to many of our references. We concentrate on research that produces specific, measured results that apply to VE research. We assume no background other than basic knowledge of computer graphics, and explain simulator terms and concepts as necessary. This paper ends with an annotated bibliography of some harder to find research results in the field of flight simulators: • The effects of display parameters, including field-of-view and scene complexity; • The effect of lag in system response; • The effect of refresh rate in graphics update; • The existing theories on causes of simulator sickness; and • The after-effects of simulator use Many of the results we cite are contradictory. Our global observation is that with flight simulator research, like most human-computer interaction research, there are very few “correct” answers. Almost always, the answer to a specific question depends on the task the user was attempting to perform with the simulator.

264 citations

29 Oct 2012
TL;DR: In this article, a survey of the literature in the field of virtual environments (VE) is presented, focusing on military literature that may be hard for traditional academics to locate via the standard journals.
Abstract: Researchers in the field of virtual environments (VE), or virtual reality, surround a participant with synthetic stimuli, The flight simulator community, primarily in the U.S. military, has a great deal of experience with aircraft simulations, and VE researchers should be aware of the major results in this field. In this survey of the literature, we have especially focused on military literature that may be hard for traditional academics to locate via the standard journals. One of the authors of this paper is a military helicopter pilot himself, which was quite useful in obtaining access to many of our references. We concentrate on research that produces specific, measured results that apply to VE research. We assume no background other than basic knowledge of computer graphics, and explain simulator terms and concepts as necessary. This paper ends with an annotated bibliography of some harder to find research results in the field of flight simulators: • The effects of display parameters, including field-of-view and scene complexity; • The effect of lag in system response; • The effect of refresh rate in graphics update; • The existing theories on causes of simulator sickness; and • The after-effects of simulator use Many of the results we cite are contradictory. Our global observation is that with flight simulator research, like most human-computer interaction research, there are very few correct answers. Almost always, the answer to a specific question depends on the task the user was attempting to perform with the simulator.

17 citations


Cited by
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Journal ArticleDOI
Ronald Azuma1
TL;DR: The characteristics of augmented reality systems are described, including a detailed discussion of the tradeoffs between optical and video blending approaches, and current efforts to overcome these problems are summarized.
Abstract: This paper surveys the field of augmented reality AR, in which 3D virtual objects are integrated into a 3D real environment in real time. It describes the medical, manufacturing, visualization, path planning, entertainment, and military applications that have been explored. This paper describes the characteristics of augmented reality systems, including a detailed discussion of the tradeoffs between optical and video blending approaches. Registration and sensing errors are two of the biggest problems in building effective augmented reality systems, so this paper summarizes current efforts to overcome these problems. Future directions and areas requiring further research are discussed. This survey provides a starting point for anyone interested in researching or using augmented reality.

8,053 citations

Journal ArticleDOI
TL;DR: A number of the primary factors that contribute to the cause of cybersickness are discussed, three conflicting cybersickenness theories that have been postulated are described, and some possible methods for reducing cyberedickness in VEs are discussed.
Abstract: An important and troublesome problem with current virtual environment (VE) technology is the tendency for some users to exhibit symptoms that parallel symptoms of classical motion sickness both during and after the VE experience. This type of sickness, cybersickness, is distinct from motion sickness in that the user is often stationary but has a compelling sense of self motion through moving visual imagery. Unfortunately, there are many factors that can cause cybersickness and there is no foolproof method for eliminating the problem. In this paper, I discuss a number of the primary factors that contribute to the cause of cybersickness, describe three conflicting cybersickness theories that have been postulated, and discuss some possible methods for reducing cybersickness in VEs.

1,031 citations

Journal ArticleDOI
TL;DR: A method for approximating polyhedral objects to support a time-critical collision-detectional algorithm that maintains its real-time performance as objects become more complicated, even as they exceed previouslyreported complexity levels by a factor of more than 10.
Abstract: This article presentsa method for approximatingpolyhedralobjects to support a time-critical collision-detectionalgorithm. The approximationsare hierarchies of spheres, and they allow the time-critical algorithm to progressivelyrefine the accuracy of its detection, stopping as needed to maintain the real-time performanceessential for interactive applications.The key to this approachis a preprocessthat automaticallybuilds tightly fitting hierarchies for rigid and articulatedobjects.The preprocessuses medial-axis surfaces, which are skeletal representations of objects. These skeletonsguide an optimizationtechniquethat gives the hierarchies accuracy properties appropriate for collision detection. In a sample application, hierarchies built this way allow the time-criticalcollision-detectionalgorithmto have acceptableaccuracy, improving significantly on that possible with hierarchies built by previous techniques. The performanceof the time-critical algorithmin this application is consistently 10 to 100 times better than a previous collision-detection algorithm, maintaining low latency and a nearIy constant frame rate of 10 frames per second on a conventional graphics workstation. The time-critical algorithm maintains its real-time performanceas objects become more complicated, even as they exceed previouslyreported complexitylevels by a factor of more than 10.

564 citations

Journal ArticleDOI
TL;DR: The challenges each of these factors present to the effective design of virtual environments and systematic approaches to the resolution of each of them are discussed.
Abstract: 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.

549 citations

Proceedings ArticleDOI
19 Mar 2016
TL;DR: By strategically and automatically manipulating FOV during a VR session, the degree of VR sickness perceived by participants can be reduced and help them adapt to VR, without decreasing their subjective level of presence, and minimizing their awareness of the intervention.
Abstract: Virtual Reality (VR) sickness can cause intense discomfort, shorten the duration of a VR experience, and create an aversion to further use of VR. High-quality tracking systems can minimize the mismatch between a user's visual perception of the virtual environment (VE) and the response of their vestibular system, diminishing VR sickness for moving users. However, this does not help users who do not or cannot move physically the way they move virtually, because of preference or physical limitations such as a disability. It has been noted that decreasing field of view (FOV) tends to decrease VR sickness, though at the expense of sense of presence. To address this tradeoff, we explore the effect of dynamically, yet subtly, changing a physically stationary person's FOV in response to visually perceived motion as they virtually traverse a VE. We report the results of a two-session, multi-day study with 30 participants. Each participant was seated in a stationary chair, wearing a stereoscopic head-worn display, and used control and FOV-modifying conditions in the same VE. Our data suggests that by strategically and automatically manipulating FOV during a VR session, we can reduce the degree of VR sickness perceived by participants and help them adapt to VR, without decreasing their subjective level of presence, and minimizing their awareness of the intervention.

383 citations