Table Of ContentDistinguished Dissertations
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Hardware Evolution: Automatic Design of Electronic Circuits in Reconfigurable Hardware by
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Masahito Hasegawa
Chris Greenhalgh
Large Scale
Collaborative Virtual
Environments
Springer
Chris Greenhalgh, BA, PhD
Faculty of Science, School of Computer Science and Information Technology,
University Park, University of Nottingham, Nottingham, NG7 2RD, UK
Series Editor
Professor c.J. van Rijsbergen
Department of Computing Science, University of Glasgow, G 12 8RZ, UK
ISBN 978-1-4471-1222-8 Springer-Verlag London Berlin Heidelberg
British Library Cataloguing in Publication Data
Greenhalgh. Chris
Large scale collaborative virtual environments. -
(Distinguished dissertations)
1. Virtual reality 2.Computer network architectures
3.Distinguished operating systems (Computers) 4.Multimedia
systems
I.Title
006
ISBN-13:978-1-4471-1222-8 e-ISBN-13:978-1-4471-0867-2
DOl: 10.1007/978-1-4471-0867-2
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress
Apart from any fair dealing for the purposes of research or private study. or criticism or review. as
permitted under the Copyright. Designs and Patents Act 1988. this publication may only be reproduced.
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or in the case of repro graphic reproduction in accordance with the terms of licences issued by the
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publishers.
© Springer-Verlag London Limited 1999
Softcover reprint of hardcover lst edition 1999
The use of registered names. trademarks etc. in this publication does not imply. even in the absence of a
specific statement. that such names are exempt from the relevant laws and regulations and therefore free
for general use.
The publisher makes no representation. express or implied. with regard to the accuracy of the information
contained in this book and cannot accept any legal responsibility or liability for any errors or omissions
that may be made.
Typesetting: Camera-ready by author
34/3830-543210 Printed on acid-free paper
To Vanessa, Susannah and Timothy.
Preface
Collaborative virtual environments (CVEs) are multi-user virtual realities which seek
to actively support communication and cooperation between distributed users.These
3D audio-graphical environments have the potential to:
• scale to very large numbers of simultaneous participants much more effectively
than other forms of (non-spatial) computer-mediated communication such as
video or audio conferencing;
• provide a unified context for communication and information, for example allow
ing an architectural team to have a tele-conference within a visualisation of a
planned building;
• maintain autonomy of individuals, and an appropriate balance of power and influ
ence between participants;
• support "natural" uses of space in communication, such as dynamic group forma
tion, gesture and gaze direction; and
• allow users to easily maintain peripheral awareness of nearby activities, and to
assess the states of systems and activities at a glance.
When we seek to meet these objectives we are faced with many technical and
conceptual challenges. For the systems whif'll do exist, we want to know how effec
tive they are and, indeed, whether our objectives are actually &chievable.
Origins
I have been researching, implementing, using and deploying collaborative virtual
environments for just over five years, first as a post-graduate student, and more
recently as a lecturer, both at the University of Nottingham. This book is my doctoral
thesis, which was one of two winners of the 1998 Distinguished Dissertations in
Computer Science competition. This competition is run by the Conference of Profes
sors and Heads of Computing (CPHC), in conjunction with the British Computer
Society (BCS), in order to select for publication a few of the best British PhDIDPhil
dissertations in computer science.
My thesis is presented here complete and unchanged, except for reformatting and
the removal of two appendices which are not relevant for publication in this form
viii Large Scale Collaborative Virtual Environments
(colour images and video presentation contents). I have also added an index to help
with selective reading and reference use. It is a great pleasure to see this in print, and
I hope that you will find it interesting and gain insight from it.
Intended Audience
There are four intended audiences for this book. First, (because of its origins as a
PhD dissertation) it is directly relevant to other researchers and post-graduate stu
dents working in the area of multi-user virtual reality. It is particularly pertinent for
researchers concerned with:
• architectures for distributed virtual reality systems;
• network requirements of these systems;
• use and user evaluation of collaborative virtual environments; and
• models of interaction and communication in space-based multi-user systems.
Second, it can be used by researchers in related areas, such as single-user virtual
reality, computer supported cooperative work and distributed systems, to gain a
detailed understanding of the issues peculiar to systems and environments of this
kind.
Third, it should be accessible to any advanced computer-literate reader wishing to
explore the current state of the art in specifically multi-user virtual reality.
Fourth, it may serve as a model for future students (one of the objectives of the
Distinguished Dissertations series) since it has been judged to be among the best cur
rent dissertations in the area of computer science. The competition also requires that
it combine a noteworthy contribution to the subject with a high standard of exposi
tion, in such a way that it is accessible to those with other specialities.
Content and Structure
This book is based around two prototype collaborative virtual environment sys
tems, MASSIVE-l and MASSIVE-2, which I have designed and implemented.
These systems realise and extend a spatial model of interaction, which provides a
conceptual and computational basis for managing communication and interaction. I
have sought to combine two major perspectives:
• the user's perspective within the everyday social world -considering the kinds of
interaction and control which are afforded to a participant in a CVE; and
• the network's perspective -considering the form and requirements of the commu
nication which facilitates this interaction.
Section 1.4 (page 13) explains the structure of the book and gives suggestions for
reading order. The overall form (from page 15) is shown below.
ix
Chapter 1. Introduction
Chapter 2. CVEs: a review
Prototype Communication
Key concept Theory Social issues
overview issues
Part I: Chapter 3: Chapter 4: Chapter 5: Chapter 6:
Direct Original MASSIVE-l Awareness Spatial Trading
relationships spatial model overview relationships
Part II: Chapter 7: Chapter 8: Chapter 9: Chapter 10:
Indirect Third party MASSIVE-2 Regions and Awareness driven
relationships objects overview awareness communication
Chapter 11. Summary, conclusions and future work
Part I deals with the concepts, design, user-oriented evaluation and network
requirements of MASSIVE-I, which is a unicast-based CVE implementing the spa
tial model of interaction of Benford and FabIen (reviewed in chapter 3).
Part II does the same for MASSlVE-2, which is a multicast-based CVE imple
menting the proposed "third party object" extension to the spatial model. (See section
2.2.2 for a comparison of unicast and multicast communication.)
Subsequent Developments
I completed this dissertation in September, 1997. Since then work has continued on
MASSIVE-2 and its successor, however thi.s cannot be integrated here because the
thesis is published "as is".
Perhaps the single most significant event of the past year has been the use of
MASSIVE-2 for staging "Out Of This World", an experiment in Inhabited Television
(see section 11.3.3). Out Of This World can be viewed as a logical extension of the
Now96 event (described in section 9.2.1). Eight inhabitants (members 9f the public
sitting at PCs wearing microphone-headsets) formed two teams that competed in a
series of co-operative games, the winners gaining the right to escape from the
doomed world. The show was projected live in a nearby auditorium to the show's
viewers (also members of the public). Each team was led by a captain, played by a
paid performer, who was immersed in the virtual world using a headset and tracking
technology. The games were overseen by a host, who appeared in the world as a
video texture. Whilst each performance took place, four virtual camera operators
filmed the action. An experienced television director mixed the final show using
standard outside broadcast equipment.
x Large Scale Collaborative Virtual Environments
Out Of This World was a great technical success, and the performances (four in
total) were coherent and accessible. The inhabitants were generally involved and able
to interact and collaborate. We believe that the event demonstrated the feasibility and
potential effectiveness of Inhabited Television. The next key areas for development
are the creation of engaging content for this format, its integration with longer-term
communities of participants (at all levels -authors, performers, inhabitants and view
ers) and the continuing quest to practically support much larger numbers of simulta
neous participants.
Acknowledgements
First and foremost, I would like to thank my supervisor, Steve Benford, for providing
an excellent environment in which to work and a firm conceptual and ideological
foundation on which to build. Our past and present collaboration has been invaluable
and most enjoyable.
I would also like to thank all those members of the Communication Research
Group, past and present, who have shared their time, friendship and interests. Dave
Snowdon made many valuable contributions, including discussion and implementa
tion. Adrian Bullock was the linchpin that made trials happen and machines work.
Maarten Stenius (a visiting researcher from SICS) ported WWW-3D to MASSlVE-2.
Many thanks also to Karsten Bormann, Rob Clarke, Neil Cook, Mike Craven, Mike
Fraser, Tony Glover, Rob Ingram, Boriana Koleva, David Lloyd, Jim Purbrick, Mina
Radenkovic, Gail Reynard, Marcus Roberts, Ian Taylor, Jolanda Tromp and Ivan
Vaghi.
Finally, I would like to thank Jon Crowcroft, my external examiner, for support
ing my submission to the Distinguished Dissertations in Computer Science competi
tion, and the panel members and other reviewers for their favourable consideration of
my work.
Abstract
This thesis is concerned with the theory, design, realisation and evaluation of
large-scale collaborative virtual environments. These are 3D audio-graphical compu
ter generated environments which actively support collaboration between potentially
large numbers of distributed users. The approach taken in this thesis reflects both the
sociology of interpersonal communication and the management of communication in
distributed systems.
The first part of this thesis presents and evaluates MASSIVE-I, a virtual reality
tele-conferencing system which implements the spatial model of interaction of Ben
ford and Fahlen. The evaluation of MASSIVE-l has two components: a
user-oriented evaluation of the system's facilities and the underlying awareness
model; and a network-oriented evaluation and modelling of the communication
requirements of the system with varying numbers of users.
This thesis proposes the "third party object" concept as an extension to the spatial
model of interaction. Third party objects can be used to represent the influence of
context or environment on interaction and awareness, for example, the effects of
boundaries, rooms and crowds. Third party objects can also be used to introduce and
manage dynamic aggregates or abstractions within the environments (for example
abstract overviews of distant crowds of participants). The third party object concept
is prototyped in a second system, MASSIVE-2.
MASSIVE-2 is also evaluated in two stages. The first is a user-oriented reflection
on the capabilities and effectiveness of the third party concept as realised in the sys
tem. The second stage of the evaluation develops a predictive model of total and
per-participant network bandwidth requirements for systems of this kind. This is used
to analyse a number of design decisions relating to this type of system, including the
use of multicasting and the form of communication management adopted.
