In the companion paper, Watson et al. (1997), we demonstrated the effectiveness of using perceptual criteria to select the amount of detail that is displayed in an immersive virtual reality (VR) system. Based upon this determination, we will now attempt to develop a principled, perceptually oriented framework to automatically select the appropriate level of detail (LOD) for each object in a scene, taking into consideration the limitations of the human visual system. We apply knowledge and theories from the domain of visual perception to the field of VR, thus optimizing the visual information presented to the user based upon solid metrics of human vision. Through a series of contrast grating experiments, a user's visual acuity may be assessed in terms of spatial frequency (c/deg) and contrast. The results of these tests can be modeled mathematically using a contrast sensitivity function (CSF). Therefore, we can use the CSF results to estimate how much visual detail the user can perceive in an object at any instant. Then, if we could describe this object in terms of its spatial frequencies, this would enable us to select the lowest LOD available without the user being able to perceive any visual change.

While virtual reality systems are used in training and in mental health treatment to simulate real-world environments, understanding the mental processing differences between artificial and real scenes has been difficult to substantiate. The ability to compare brain processing in virtual and real exposures could provide an objective quantitative comparison. In this paper, we demonstrate that verifiable EEG measurements of mental activity can be obtained while subjects are immersed in a virtual reality headset. Using standard commercial EEG measuring equipment, we recorded EEG activity in similar virtual and real scenes for 14 people encountering four different test conditions. We discuss the systematic exploration of the recording problems and the steps taken to verify the data. This data is further analyzed to conclude that differences do exist between real and virtual image processing, with variations affected more by subject and task than by which area of the brain is processing the image. We discuss some possible reasons for these findings.

This paper describes premises of a video, Zircus , presenting a design for a virtual environment. The video is a basis for discussion—a sketch, rather than a specification, of a virtual playspace and interactions that can happen there. The playspace is conceived as a learning environment in which constructive activities can focus thinking on certain sets of ideas. Conversations within the multiuser environment can also be conducive to learning, as well as to developing an online community. These actions and conversations would depend on a future system combining technologies in networked graphics, speech, AI, various input devices, and high-level software for constructing animations and audio/video sequences. Taking the ideas in Zircus from sketch to implementation will require contributions from researchers in a range of disciplines, including architectural design, film media, learning theory, and computer science.

This paper describes an implementation of “robotic graphics,” in which forces and torques are provided in virtual environments by the method of interacting with robots that are not attached to the body. The demonstration simulates a flat control panel containing an assortment of switches by using an immersive virtual reality head-mounted display, electro-magnetic and videometric tracking, and a robot that holds a turret containing one of each of the types of switches. The robot dynamically presents the switches to be touched in a just-in-time only-as-needed basis. Results are presented regarding visual/force registration for finger tracking and human performance.

This is an extension of an earlier paper (Sheridan, 1992) that considered alternative meanings and significance of “presence,” the experience of “being there,” commonly called “telepresence” in the case of remote control or teleoperation, and called “virtual presence” in the case of computer-generated simulation. In both cases presence can include feedback to the human senses of vision, hearing, and haptics, both kinesthetic and cutaneous. Presence is discussed here in terms of alternative subjective meanings, operational measurements, and meaningful experimental comparisons. Three practical approaches to measurement of presence are compared, including elicitation of “natural” neuromuscular or vocal responses, single or multidimensional subjective scaling, and ability to discriminate the real and immediate environment from that which is recorded/transmitted or synthesized. A new proposal, fitting into the third category, is to measure presence according to the amount of noise required to degrade the real and virtual stimulation until the perceived environments are indiscriminable. The author also opines on the stimulus magnitude, space, and time attributes of human interactions with a tele- or virtual environment.

An operators' sense of remote presence during teleoperation or use of virtual environment interfaces is analyzed as to what characteristics it should have to qualify it as an explanatory scientific construct. But the implicit goal of designing virtual environment interfaces to maximize presence is itself questioned in a second section in which examples of human—machine interfaces beneficially designed to avoid a strong sense of egocentric presence are cited. In conclusion, it is argued that the design of a teleoperation or virtual environment system should generally focus on the efficient communication of causal interaction. In this view the sense of presence, that is of actually being at the simulated or remote workplace, is an epiphenomena of secondary importance for design.

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.

The primary purpose of this study was to investigate the effectiveness of virtual environment technology in the area of psychotherapy. In particular, this study investigated the effectiveness of virtual environment desensitization (VED) in the treatment of agoraphobia (fear of being in places or situations from which escape might be difficult or embarrassing). Sixty undergraduate college students served as subjects. Thirty subjects served in the experimental group and the other 30 served as a control group. Subjects' degree of fear/anxiety was measured using two instruments, the Attitude Towards Agoraphobia Questionnaire (ATAQ) and the Subjective Units of Discomfort Scale (SUDS). Only subjects in the experimental group were exposed to the VED treatment. The scores of the control group did not change significantly, while both ATAQ and SUDS scores decreased significantly for the experimental group. The average SUDS scores of the experimental group decreased steadily across sessions, indicating steady improvement with treatment. It is hoped that this research will be a first step toward the utilization of virtual environment technology in providing more effective, economical, and confidential treatment of psychological disorders.