This paper explores the issues involved in designing and developing network software architectures for large scale virtual environments. We present our ideas in the context of NPSNET-IV, the first 3D virtual environment that incorporates both the IEEE 1278 Distributed Interactive Simulation (DIS) application protocol and the IP Multicast network protocol for multi-player simulation over the Internet.

The development of multi-user networked virtual worlds has become a major area of interest in the computer and communications fields. However, there has been little effort to provide a coherent framework for understanding distributed virtual environments (VEs). In this paper we discuss VEs in the context of how communications, views, data, and processes are distributed while emphasizing those aspects critical to scaling environments. We find most of the systems described in this paper scale to accommodate a handful of users. We also discuss why systems which demand strong data consistency, causality, and reliable communications at the same time while supporting real-time interaction are not likely to scale very well. Furthermore, if the systems are to be geographically dispersed, then highspeed, multicast communication is required. . KEYWORDS: Virtual Reality, Distributed Interactive Simulation, Internet Protocol Multicast, Distributed Interactive Entertainment, Large-scale Virtual E...

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.

In this paper we present an approach to applying virtual reality in architectural design and collaborative visualization which emphasizes the use of multiple perspectives. These perspectives, including multiple mental models as well as multiple visual viewpoints, allow virtual reality to be applied in the earlier, more creative, phases of the design process, rather than just as a walkthrough of the final design. CALVIN, a prototype interface which implements these ideas, has been created using the CAVE tm virtual reality theatre. 1. Introduction Three dimensional walk-throughs employing an "inside-out" perspective have traditionally been the raison d'etre for virtual reality (VR) in architectural design[2]. This "inside-out" perspective allows a person to see the environment as if standing inside the environment and looking out at the surroundings. We believe this limits the usefulness of VR to only the final stages of the architectural design process, where a CAD model can be given...

The Environment Manager (EM) is a high-level tool for constructing both single user and multi-user virtual environments. A script file is used to initialize and run virtual worlds. Independent applications can share information and cooperate with each other across the Internet. EM reduces the effort required to produce a networked virtual world by providing highlevel support for application replication, network configuration, communication management and concurrency control. This paper describes the architecture and implementation of EM. 1 Introduction With many single-user Virtual Reality(VR) applications being successfully implemented [3, 12, 13, 10, 17], Networked Virtual Reality is now becoming a hot topic. Networked Virtual Reality refers to virtual environments where multiple users connected by a network can share information with each other. The production of good VR worlds, whether single user or networked, requires a considerable amount of design and programming time. Expert...

Abstract—A distributed virtual walkthrough environment allows users connected to the geometry server to walk through a specific place of interest, without having to travel physically. This place of interest may be a virtual museum, virtual library or virtual university. There are two basic approaches to distribute the virtual environment from the geometry server to the clients, complete replication and on-demand transmission. Although the on-demand transmission approach saves waiting time and optimizes network usage, many technical issues need to be addressed in order for the system to be interactive. g�˜��‡—� � is a web-based distributed virtual walkthrough system developed based on the on-demand transmission approach. It achieves the necessary performance with a multiresolution caching mechanism. First, it reduces the model transmission and rendering times by employing a progressive multiresolution modeling technique. Second, it reduces the Internet response time by providing a caching and prefetching mechanism. Third, it allows a client to continue to operate, at least partially, when the Internet is disconnected. The caching mechanism of g�˜��‡—�� tries to maintain at least a minimum resolution of the object models in order to provide at least a coarse view of the objects to the viewer. All these features allow g�˜��‡—� � to provide sufficient interactivity to the user for virtual walkthrough over the Internet environment. In this paper, we demonstrate the design and implementation of g�˜��‡—��. We investigate the effectiveness of the multiresolution caching mechanism of g�˜��‡—� � in supporting virtual walkthrough applications in the Internet environment through numerous experiments, both on the simulation system and on the prototype system. Index Terms—Distributed virtual environments, model prefetching, multiresolution caching, multiresolution modeling, virtual walkthrough. I.

Declaration 13 Copyright Notice 14 Acknowledgements 15 1

In this paper we describe CALVIN, an immersive multimedia approach to applying virtual reality in architectural design and collaborative visualization emphasizing heterogeneous perspectives. These perspectives, including multiple mental models as well as multiple visual viewpoints, allow virtual reality to be applied in the earlier, more creative, phases of design, rather than just as a walk-through of the finished space. CALVIN's interface employs visual, gestural, and vocal input to give the user greater control over the virtual environment. A prototype of CALVIN has been created and used in the CAVE(tm) virtual reality theatre. 1 Introduction As multimedia systems evolve beyond the twodimensional desktop they will allow users to engage in richer interaction with multimedia information. Virtual reality (VR) can provide a medium for this interaction allowing users to experience an immersive multimedia (or immersimedia) environment. Traditionally the raison d'etre for immersive applic...

. Research areas that require interactive visualization of simulation data

Distributed virtual environments allow users at different geographical locations to share and interact within a common virtual environment via a local network or through the Internet. To deliver a good performance for such applications, we need to address several issues in different research disciplines. First, we must be able to model virtual objects effectively. The recently developed multi-resolution techniques for object modeling are of great value here, since they are capable of simplifying the object models and therefore reducing the time to render them. This may greatly reduce the demand for rendering performance on the client machines. Second, with the constraint of the limited bandwidth of the Internet, we need to reduce the response time by reducing the amount of data requested over the network. Caching of suitable object models of high affinity will reduce the amount of data requested over the network for a faster response time. Prefetching object models by predicting those ...