Oth law of model dynamics: In a finite (and usually very short) amount of time, users of a graphics system will generate a model that shall bring said system to its knees. The purpose of this paper is to discuss our experiences with the impact of megamodels on interactive virtual environments. We consider a megamodel to be any model that causes the Oth law of model dynamics to come into effect. We will demonstrate how working with megamodels quickly reveals the limitations of the graphics hardware and software being used to support the virtual environment. We will give examples, based upon our experiences on the Architectural Walkthrough Project here at the University of North Carolina at Chapel Hill (UNC), of the kinds of extra effort required to overcome these limitations.

We discuss the evolution and current status of investigations at our Graphics, Visualization, and Virtual Environments Laboratory. The progression of user interface technology has led us from display systems evaluation, to performance studies of graphics workstations, stereoscopic and head-mounted displays, user-input devices, and interactive techniques for virtual environments. We have been involved in prototyping applications for terrain visualization, situation awareness for command and control, maintenance procedures training, and interactive design. Our current emphasis is on developing techniques for rapid modeling of virtual environments, to support mission planning, rehearsal, and interactive design and visualization. We discuss in detail three examples of these applications, and we present a set of guidelines that we have found to be useful for quickly constructing effective virtual environments.

The Air Force Institute of Technology Virtual Environments, 3-D Medical Imaging, and Computer Graphics Laboratory is investigating the 3-D computer graphics, user-interface design, networking protocol, and software architecture aspects of distributed virtual environments. In this paper we describe the research projects that are underway in the laboratory. These projects include the development of an aircraft simulator for a distributed virtual environment, projects for observing, analyzing, and understanding virtual environments, a space virtual environment, a project that incorporates “live” aircraft range data into a distributed virtual environment, a virtual environment application framework, and a project for use in a hospital emergency department. We also discuss the research equipment infrastructure in the laboratory, recent publications, and the educational services we provide.

The Swedish multiinstitutional research program MultiG spawned a number of research projects concerned with telecommunication, telecollaboration, and telepresence. One of these projects is DIVE (Distributed Interactive Virtual Environments), a multiuser virtual reality system developed jointly by the Swedish Institute of Computer Science and the Royal Institute of Technology in Stockholm, Sweden. DIVE is used as the platform for research in collaborative work in virtual spaces. In cooperation with the universities of Lancaster, Manchester, and Nottingham, the DIVE group has developed a spatial model for interaction. In this model each participant defines subspaces for their presence and attention. The intersection of those subspaces provides for varying degrees of mutual awareness, which is presumed to support more natural human-human interaction in virtual environments.

The Institute for Simulation and Training (IST) was created in 1984 by the University of Central Florida to provide research support to the U.S. Department of Defense in the area of simulation-based training. In 1989, IST's Visual Systems Laboratory (VSL) was inaugurated. Focal areas of research at VSL include distributed realtime physical simulation, interoperability among networked simulators, the application of virtual environments to education, training, and design, and head-mounted display technology. Section 1 describes the history of IST and VSL, and VSL's early projects. Section 2 surveys current research projects in three main areas: dynamic environments, interoperability, and virtual environments. Section 3 describes service and educational activities, and Section 4 provides insight into future research plans.

The overall goals of the Center for Human Modeling and Simulation are the investigation of computer graphics modeling, animation, and rendering techniques. Major focii are in behavior-based animation of human movement, modeling through physics-based techniques, applications of control theory techniques to dynamic models, illumination models for image synthesis, and understanding the relationship between human movement, natural language, and communication.

Developing virtual worlds using toolkits and conventional programming-based approaches is a tedious, time-consuming, and often frustrating task. Too much learning of the toolkits and the basic development technology is necessary before the development can start. Even after that, it takes a long time to develop, test, and modify virtual worlds. At ISS, we are following a highly interactive and visual approach to virtual world construction, which allows virtual world designers to work with high-level concepts. This approach facilitates exploration in design and rapid prototyping. To achieve our goal, we are focusing on the following four base technologies: Bricks, a toolkit to support the development of virtual worlds; WorldNet, a toolkit to support the development of network-based virtual worlds; VizNet, a system that helps visualize a large collection of objects; and the Virtual Workbench, a crafting environment that uses virtual reality to build and manage objects.

Virtual environment research involves a number of related problems from a variety of domains. A joint research at the George Washington University and the Naval Research Laboratory is bringing together issues from these domains to study the factors that contribute to an integrated virtual environment. The research can be divided into three general categories: human factors, motion control, and sound synchronization. Human factors issues involve the development of new paradigms for movement and navigation, essential for performance of general tasks in virtual spaces. Novel approaches to motion control are being explored to help users of virtual environments interact and control virtual objects. This involves both interactive control as well as automation through evolutionary approaches. The sounds being generated as a result of these motions are modeled with compositional techniques to parameterize and synchronize them to the events in the environment. The research is being approached from both a fundamental point of view typical of an academic environment as well as from an application oriented point of view of interest to the Navy. The cooperative relationship has benefited both the George Washington University and the Naval Research Laboratory.

The Naval Postgraduate School Networked Vehicle Simulator IV (NPSNET-IV) is a low-cost, student-written, real-time networked vehicle simulator that runs on commercial, off-the-shelf workstations (the Silicon Graphics IRIS family of computers). NPSNET-IV has been developed at the Naval Postgraduate School's (NPS) Department of Computer Science in the Graphics and Video Laboratory. It utilizes Simulation Network (SIMNET) databases and SIMNET and Distributed Interactive Simulation (DIS) networking formats. The DIS networking format is flexible enough to allow multiple players to game over the Internet. The availability of NPSNET-IV lowers the entry costs of researchers wanting to work with SIMNET, DIS, and follow-on systems. Without the contributions of the department's M.S. and Ph.D. candidates, the NPSNET project would be impossible to maintain and continue. The diversity of their interests accounts for the broad range of research areas within the project.