Manipulation in immersive virtual environments is difficult partly because users must do without the haptic contact with real objects they rely on in the real world to orient themselves and their manipulanda. To compensate for this lack, we propose exploiting the one real object every user has in a virtual environment, his body. We present a unified framework for virtual-environment interaction based on proprioception, a person's sense of the position and orientation of his body and limbs. We describe three forms of body-relative interaction: . Direct manipulation---ways to use body sense to help control manipulation . Physical mnemonics---ways to store/recall information relative to the body . Gestural actions---ways to use body-relative actions to issue commands Automatic scaling is a way to bring objects instantly within reach so that users can manipulate them using proprioceptive cues. Several novel virtual interaction techniques based upon automatic scaling and our proposed fr...

We introduce a framework for supporting crowds of participants in collaborative virtual environments (CVEs). The framework is realised as an extension to our previous spatial model of interaction and aims to provide greater scaleability and flexibility for communication between the inhabitants of virtual worlds. Our framework introduces an explicit crowd mechanism into CVEs in order to support the formation and activation of different kinds of crowd with different effects on mutual awareness and communication (achieved through the use of aggregation techniques combined with awareness adaptation). We present a demonstration application called the Arena- a shared space for staging on-line performances in front of a live audience.

The Omni-Directional Treadmill (ODT) is a revolutionary device for locomotion in large-scale virtual environments. The device allows its user to walk or jog in any direction of travel. It is the third generation in a series of devices built for this purpose for the U.S. Army's Dismounted Infantry Training Program. We first describe the device in terms of its construction and operating characteristics. We then report on an analysis consisting of a series of locomotion and maneuvering tasks on the ODT. We observed user motions and system responses to those motions from the perspective of the user. Each task is described in terms of what causes certain motions to trigger unpredictable responses causing loss of balance or at least causing the user to become consciously aware of their movements. We conclude that the two primary shortcomings in the ODT are its tracking system and machine control mechanism for centering the user on the treads.

Bamboo is a portable system supporting real-time, networked, virtual environments. Unlike previous efforts, this design focuses on the ability for the system to dynamically configure itself without explicit user interaction, allowing applications to take on new functionality after execution. In particular, this framework facilitates the discovery of virtual environments on the network at runtime. Fundamentally, Bamboo offers a compatible set of mechanisms needed for a wide variety of real-time, networked applications. Also included is a particular combination of these mechanisms supporting a dynamically extensible runtime environment. This paper serves as a general introduction to Bamboo. It describes the system's architecture, implementation, and future directions. It also shows how the system can facilitate the rapid development of robust applications by promoting code reuse via communitywide exchange.

Diamond Park is a social virtual reality system in which multiple geographically separated users can speak to each other and participate in joint activities. The central theme of the park is cycling. Human visitors to the park are represented by 3D animated avatars and can explore a square mile of 3D terrain. In addition to human visitors, the park hosts a number of computer simulations including tour buses and autonomous animated figures. Diamond Park is

Distributed, real-time multiplayer computer games (MCGs) are in the vanguard of utilizing the networking possibilities. Although related research have been done in military simulations, virtual reality systems, and computer supported cooperative working, the suggested solutions diverge from the problems posed by MCGs. With this in mind, this paper provides a concise overview of four aspects affecting networking in MCGs. Firstly, networking resources (bandwidth, latency, and computational power) set the technical boundaries within which the MCG must operate. Secondly, distribution concepts encompass communication architectures (peer-to-peer, client/server, server-network), and both data and control architectures (centralized, distributed, replicated). Thirdly, scalability allows the MCG to adapt to the resource changes by parametrization. Finally, security aims at fighting back against cheating and vandalism, which are common in online gaming. Keywords---Computer games, networking, online entertainment, distributed interactive simulation, virtual environments.

Over the past decade, software architecture research has emerged as the principled study of the overall structure of software systems, especially the relations among subsystems and components. From its roots in qualitative descriptions of useful system organizations, software architecture has matured to encompass broad explorations of notations, tools, and analysis techniques. Whereas initially the research area interpreted software practice, it now offers concrete guidance for complex software design and development. We can understand the evolution and prospects of software architecture research by examining the research paradigms used to establish its results. These are, for the most part, the paradigms of software engineering. We advance our fundamental understanding by posing research questions of several kinds and applying appropriate research techniques, which differ from one type of problem to another, yield correspondingly different kinds of results, and require different methods of validation. Unfortunately, these paradigms are not recognized explicitly and are often not carried out correctly; indeed not all are consistently accepted as valid. This retrospective on a decade-plus of software architecture research examines the maturation of the software architecture research area by tracing the types of research questions and techniques used at various stages. We will see how early qualitative results set the stage for later precision, formality, and automation and how results build up over time. This generates advice to the field and projections about future impact. Keywords: Software architecture, research paradigms 1.

We present a strategy for rendering in distributed virtual environments. A geometry database is maintained by a server, while users invoke individual clients to interact with the environment. Instead of downloading a complete copy of the geometry data, the data is distributed on demand, thus gaining significant savings in network bandwidth. Our strategy combines several techniques, including levels of detail, progressive refinement and graceful degradation to deliver the data "just in time" over the network to the rendering process. The method allows operate on a tight resource budget, which important if attempting to use low cost systems for virtual reality applications.

Virtual reality has become an increasingly familiar part of the science of visualization and communication of information. This, combined with the increase in connectivity of remote sites via high-speed networks, allows for the development of a collaborative distributed virtual environment. Such an environment enables the development of supercomputer simulations with virtual reality visualizations that can be displayed at multiple sites, with each site interacting, viewing, and communicating about the results being discovered. The early results of an experimental collaborative virtual reality environment are discussed in this paper. The issues that need to be addressed in the implementation, as well as preliminary results are covered. Also provided are a discussion of plans and a generalized application programmers interface for CAVE to CAVE will be provided. 1 Introduction Sharing a visualization experience among remote virtual environments is a new area of research within the field ...

We describe a new 3D scene streaming approach for remote walkthroughs. In a remote walkthrough, a user on a client machine interactively navigates through a scene that resides on a remote server. Our approach allows a user to walk through a remote 3D scene, without ever having to download the entire scene from the server. Our algorithm achieves this by selectively transmitting only small parts of the scene and lower quality representations of objects, based on the user's viewing parameters and the available connection bandwidth. An online optimization algorithm selects which object representations to send, based on the integral of a benefit measure along the predicted path of movement. The rendering quality at the client depends on the available bandwidth, but practical navigation of the scene is possible even when bandwidth is low.