Conference Paper

Maximising Concurrency and Scalability in a Consistent, Causal, Distributed Virtual Reality System Whilst Minimising the Effect of Network Delays.

Dept. of Cybern., Reading Univ.
DOI: 10.1109/ENABL.1997.630808 Conference: 6th Workshop on Enabling Technologies (WET-ICE '97), Infrastructure for Collaborative Enterprises, 18-20 June 1997, MIT, Cambridge, MA, USA, Proceedings
Source: DBLP


The development of large scale virtual reality and simulation systems have been mostly driven by the DIS and HLA standards community. A number of issues are coming to light about the applicability of these standards, in their present state, to the support of general multi-user VR systems. This paper pinpoints four issues that must be readdressed before large scale virtual reality systems become accessible to a larger commercial and public domain: a reduction in the effects of network delays; scalable causal event delivery; update control; and scalable reliable communication. Each of these issues is tackled through a common theme of combining wall clock and causal time-related entity behaviour, knowledge of network delays and prediction of entity behaviour, that together overcome many of the effects of network delays.

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Available from: David Roberts
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    • "In a related work, Roberts and Sharkey [9] describe the use of a sufficient causal ordering for an arena-like distributed virtual reality system named PaRADE [9]. They verified through implementation experiences the performance benefits of using a relaxed mechanism to provide memory consistency over a network. "
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    • "• Time Management: Synchronize events or wall clocks among participants. Events can be pre-empted or delayed to maintain consistency [11] [12]. • Priority Scheduling: Data essential to maintaining consistency is sent with the highest priority [13]. "
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    • "MASSIVE-1 had no support for sub-objects, and MASSIVE-2 had only limited support; this was because of unresolved issues in reasoning about compound objects in the spatial model of interaction. • It should implement proposals for data consistency and ameliorating the effects of network delay from the University of Reading [1]. • It should provide a route to support heterogeneous computers and networks, including domestic users with modem-based connections. "
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    ABSTRACT: MASSIVE-3 is our third generation of Collaborative Virtual Environment (CVE) system. This paper describes the goals, design and implementation of key aspects of the MASSIVE-3 system, and in particular its support for data consistency, and world structuring and interest management. MASSIVE-3 adopts a distributed database model, in which all changes to items in the database are represented by explicit events that are themselves visible to the system. Networking is logically multicast, but physically client-server (the reasons for this are explained). MASSIVE-3 makes application behaviours explicitly visible within the database in the form of "Behaviour" data items. MASSIVE-3 implements and extends work on consistency by the University of Reading. In particular, it adds an explicit "Update Request" data item, which allows the system to support a number of different consistency mechanisms within a single virtual world. World structuring in MASSIVE-3 extends the notion of "Locales" from the SPLINE system to include distinctions based on functional class, organisational scope and fidelity. It also allows flexible and general replication and rendering policies to be specified and used for interest management.
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