Large-scale Collaborative Virtual Environment Research Articles

Foreword to: Special issue on virtual environments

The usage of virtual environments (VEs) in various application fields has significantly increased in recent years. The explosive advancement of commodity graphics hardware, immersive displays and tracking technology allows for the exploration of new approaches in the design of immersive interfaces which increase the level of engagement between the user and the simulated environment. The Eurographics Symposium on Virtual is a forum for dissemination of the latest research results in VEs. The 14th EGVE symposium was held in Eindhoven, The Netherlands on May 29–30, 2008. This issue contains revised and expanded versions of the three best papers selected from the Proceedings of EGVE 2008. One of the challenges in designing effective immersive interfaces is the representation of body position/orientation in the environment and an accurate updating of this representation when the body–environment relationship changes. The paper Influence of the size of the field-of-view on motion by Pretto et al. presents two experiments that aim to determine the effect of field-of-view on the effectiveness of optical flow for estimation of the perceived amplitude of rotations about the body vertical axis and the perceived speed of forward translations. Results are reported that suggest that large field-of-view are not required to estimate the amplitude of visual rotations about the vertical axis of the body, whereas field-of-views of at least 60° are advisable when speed perception relies on optic flow information. The second paper, Using Mobile Group Dynamics and Virtual Time to improve teamwork in large-scale Collaborative Virtual Environments by Dodds et al. addresses how interfaces of Collaborative Virtual can be improved for synchronous and asynchronous collaboration. The authors investigate how teleporting and virtual time affect human behavior in task- and team-specific goals. They found that virtual time simulated communication between the participants. They also found that their multiple views and teleporting functionality did increase communication and allowed for an increase of the distance between participants. It has been said that there is no silver bullet in motion tracking. Indeed, choosing the right motion traker entails a trade-off between different requirements by VE designess. The third paper, A Simulator-based Approach to Evaluating Optical Trackers by Smit et al. proposes a simulation framework to evaluate the performance of model-based optical trackers. The framework can be used to evaluate and compare the performance of different trackers under various conditions. These input conditions can model important aspects, such as the interaction task, input device geometry, camera properties and occlusion. In this way, designers of VEs can use the framework to study various conditions affecting optical tracking performance. This special issue brings together original research and contributions in VEs. We expect that it will generate novel and exciting ideas to further this field and sincerely hope you enjoy it.

Using mobile group dynamics and virtual time to improve teamwork in large-scale collaborative virtual environments

Mobile group dynamics (MGDs) assist synchronous working in collaborative virtual environments (CVEs), and virtual time (VT) extends the benefits to asynchronous working. The present paper describes the implementation of MGDs (teleporting, awareness and multiple views) and VT (the utterances of 23 previous users were embedded in a CVE as conversation tags), and their evaluation using an urban planning task. Compared with previous research using the same scenario, the new MGD techniques produced substantial increases in the amount that, and distance over which, participants communicated. With VT participants chose to listen to a quarter of the conversations of their predecessors while performing the task. The embedded VT conversations led to a reduction in the rate at which participants traveled around, but an increase in live communication that took place. Taken together, the studies show how CVE interfaces can be improved for synchronous and asynchronous collaborations, and highlight possibilities for future research.

MACVE: A Mobile Agent Based Framework for Large-Scale Collaborative Virtual Environments

The Collaborative Virtual Environment (CVE) is a promising technology which provides an online shared virtual world for geographically dispersed people to interact with each other. However, the scalability of existing CVE systems is limited due to the constraints in processing power and network speed of each participating host. In this paper, a mobile agent based framework for large-scale CVE, MACVE, is proposed to support a large number of concurrent participants in a CVE with a large amount of evolving virtual entities. In MACVE, the CVE system is decomposed into a group of collaborative mobile agents, each of which is responsible for an independent system task. These agents can migrate or clone dynamically at any suitable participating host including traditional servers and qualified user hosts to avoid the potential bottleneck, which can improve the scalability of CVE. Our prototype system has demonstrated the feasibility of the proposed framework.

AN AUTONOMOUS DECENTRALIZED MULTI-SERVER FRAMEWORK FOR LARGE SCALE COLLABORATIVE VIRTUAL ENVIRONMENTS

Collaborative Virtual Environment (CVE) is a promising technology which provides an online shared virtual world to the geographically dispersed people to interact with each other. However, the scalability of existing CVE system is limited due to the constraints in processing power and network speed of each participating host. Large scale CVE (LCVE) that supports a large number of concurrent participants and a large amount of evolving virtual entities is not easy to achieve. In this paper, an autonomous decentralized grid based mobile agent framework for large scale CVE — MACVE is proposed. In MACVE, LCVE software system is decomposed into a group of collaborative mobile agents, each of which is responsible for an independent system task. Agents can migrate or clone dynamically at any suitable participating host (grid node) include traditional servers and qualified user hosts to avoid bottleneck, which can improve the scalability of LCVE. Therefore, MACVE is a logically multi-server architecture while the server workload is autonomously decentralized. Our system prototype and evaluation has demonstrated the feasibility of the proposed framework.

Supporting Rich And Dynamic Communication In Large-Scale Collaborative Virtual Environments

We focus on the problem of constructing collaborative virtual environments (CVEs) that scale to large numbers of simultaneous participants and yet which still afford rich and varied possibilities for communication. This is achieved by extending our previously defined spatial model of interaction for CVEs to include third-party objects that provide support for contextual factors in awareness calculations and that enhance scaleability. Third parties can have two effects on awareness: attenuation or amplification of existing awareness relationships, and the introduction of new aggregate awareness relationships. We propose a range of applications for third-party objects including world structuring regions, aggregate views, dynamic crowds of participants, common foci, representational and group services, and dynamic load management. We also discuss how the third-party concept relates to other approaches to structuring virtual environments such as tiles, zones, and locales. We then present an implementation, the MASSIVE-2 system, focusing on its network architecture which is based on a dynamic and selfconfiguring hierarchy of multicast groups. Finally, we describe four demonstration applications that have been developed in MASSIVE-2: an environment for staging a public poetry performance that includes semiprivate zones for social interaction; the Panoptican Plaza, which demonstrates a variety of differently bounded regions; a collaborative 3-D Web browser that groups pages into server regions; and the Arena, a performance space that supports both static and mobile crowd aggregations of groups of participants.