For entertainment applications, a successful virtual experience based on a head-mounted display (HMD) needs to overcome some or all of the following problems: entering a virtual world is a jarring experience, people do not naturally turn their heads or talk to each other while wearing an HMD, putting on the equipment is hard, and people do not realize when the experience is over. In the Electric Garden at SIGGRAPH 97, we presented the Mad Hatter's Tea Party, a shared virtual environment experienced by more than 1,500 SIGGRAPH attendees. We addressed these HMD-related problems with a combination of back story, see-through HMDs, virtual characters, continuity of real and virtual objects, and the layout of the physical and virtual environments.

This paper is an introductory level tutorial describing how to implement a distributed multiparticipant virtual environment (VE). This tutorial is intended for students who are competent programmers and who now wish to implement a distributed multiparticipant application. We describe the fundamental concepts of distributed computing for multiplayer simulations and provide a concrete example, including C source code available via the Internet. The template program demonstrates a simple multiplayer, distributed application, where each player controls the position of a space ship, and communicates the ship's position data over the network. The template uses broadcast communication and a technique called dead-reckoning to improve performance. We give detailed instructions on how to obtain and modify the template, so that students can quickly create their own distributed applications. We conclude by briefly discussing advanced issues that are important when constructing more sophisticated multiparticipant VEs.

The Tailor project allows physically disabled users to provide real-time analog input to computer applications. We use a Polhemus™ tracking device and create a custom tailored mapping from each user's best range and type of motion into the analog control signal. The application is a simple video game based on Pong , where the analog input controls the position of the player's paddle. A group of able-bodied subjects was able to correctly hit the ball with the paddle 77% of the time, and a comparison group of children with cerebral palsy performed at the 50% level. More than half the disabled users were able to perform at a higher level than the worst able-bodied user.

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.