Table Of ContentSeries Editors
W. Hansmann
W. T. Hewitt
W. Purgathofer
M. Gobel, J. David,
P. Slavik, 1. 1. van Wijk (eds.)
Virtual Environments
and Scientific Visualization '96
Proceedings of the Eurographics Workshops
in Monte Carlo, Monaco,
February 19-20, 1996,
and in Prague, Czech Republic,
April 23-25, 1996
Eurographics
SpringerWienN ewYork
OI Dr. Martin Gobel
GMD Forschungszentrum. lnformationstechnik, Sankt Augustin,
Federal Republic of Germany
Prof. Dr. Jacques David
CEAJDI, CEo Saclay, Gifsur Yvette, France
Dr. Pavel Slavik
Department of Computer Science, Czech Technical University, Prague, Czech Republic
Dr. Jarke J. van Wijk
Netherlands Energy Research Foundation ECN, Energy Engineering,
Peuen, The Netherlands
This work is subject to copyright.
All rights are reserved, whether the whole or part of the material is concerned, specifically
those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by
photocopying machines or similar means, and storage in data banks.
© 1996 Springer-Verlag/Wien
Typesetting: Camera ready by authors
Graphic design: Ecke Bonk
With 169 partly coloured Figures
ISSN 0946-2767
ISBN-13: 978-3-211-82886-1 e-ISBN-13: 978-3-7091-7488-3
001: 10.1007/978-3-7091-7488-3
Preface
The third workshop on Virtual Environments took place on February 19-20 in
conjunction with the annual IMAGINA conference in Monte Carlo. The workshop
asked for contributions to cover coexistence, communication and collaboration in
Virtual Environments. Nineteen contributions were selected by an international
programme committee which additionally invitedJ. Nomura (MEC, Japan) andJ. Kent
(SGI, US) for talks on applications of virtual environments in Japan and to discuss the
VRML relationship to virtual environments.
Revised versions of the workshop presentations are included in this book. The first
group of four papers from Austria, the UK, Germany and Sweden discusses VE system
design and architecture issues as well as experience with novel programming style for
virtual worlds. Mixed reality in a teleconferencing and in a telepresence experiments
are reported from Germany and from Sweden.
An algorithm session introduced to several techniques for virtual environments,
such as the quick elimination of polytopes from Hongkong, camera based tracking and
morphing from Germany. On the second workshop day, human actors and crowd
simulation were presented by Swiss and French reseachers.
A further workshop session dealt with modeling aspects in virtual environments.
Work based on B-spline modeling (UK) and the impact of concurrent multi-user
modeling (France) were demonstrated.
The final paper session of the workshop included papers from various application
areas, such as a surgery support system (Japan), the distributed virtual reality lab which
is a UK research initiative, applications in geographic information systems (Nether
lands), in engineering (Switzerland) and in virtual housing systems (Japan).
Around fourty workshop participants discussed the contributions very heavily
during the two days.
As a conclusion, we can say that with its third workshop Eurographics has
established the VE workshop as an annual event which serves as a forum for
information exchange in VE research in Europe. In all of the 3 workshops, major
European VE research labs were presenting and discussing their advance results.
The workshop itself and its preparation was sponsored by ONR - Office of Naval
Resarch (US), EDF (France), INA-IMAGINA (France), CEA (France) and GMD
(Germany).
The workshop secretary was provided by Tatjana Neiss from IGD Germany. Atthis
place we would like to thank all-the sponsors, the secretary and the local organization.
Without their contributions the workshop would not have taken place.
*
The seventh workshop on Visualization in Scientific Computing took place on April
23-25 in Prague (Czech Republic). It was for the first time that an event like this was
held in Central and Eastern Europe. One of the workshop's results was the impulse for
the promotion of Scientific Visualization in this region. Papers submitted for this
workshop were evaluated by an international programme committee.
VI
Besides papers accepted for presentation also two invited lectures were given:
G. Nielson (USA): Multiresolution Modelling in Scientific Visualization and
V. Hlavac (CZ): Computer Vision and Scientific Visualization. In both lectures new
views on some topics in Scientific Visualization were given.
For these proceedings twelve papers were selected. Revised versions of these
papers are included in this book. The papers can be divided into four groups: Volume
Rendering, User Interfaces in Scientific Visualization, Architecture of Scientific
Visualization Systems, and Flow Visualization. The papers in the first group are papers
from Italy, Germany, Slovakia, and the Netherlands. The main stress was put on the
speeding up of volume rendering algorithms and on their better accuracy. The second
group of papers contains papers from Germany dealing with proper use ofe lements and
methods in the field of User Interfaces specific for Scientific Visualization applica
tions. Innovative research from Fraunhofer Institute describes the use of VR tech
niques in the field of Scientific Visualization. Papers from the Netherlands, Czech
Republic and the United Kingdom forms the third group of papers targeted to
Architecture of Scientific Visualization Systems. The last group contains results from
research in traditional area of Scientific Visualization - Flow Visualization. Improved
techniques for this area were presented. All papers presented set up a very good base
for discussions in which all 40 workshop participants took part.
Besides the authors we want to thank the Programme Committee that had to
evaluate in a short time the papers submitted. The organization of the workshop could
not have been manageable without the help of the Department of Computer Science
and Engineering at Czech Technical University in Prague and the Czech ACM
Chapter. Special thanks should be expressed to Petr Felkel, Jan Vorlicek, Bozena
Mannova, Jiri Zara, and Bedrich Benes. Without their help both the Workshop and the
book would not have come into life.
Martin Gobel, Jacques David,
Pavel Slavik, Jarke J. van Wijk
Contents
Virtual Environments '96
D. Schmalstieg, M. Gervautz, P. Stieglecker: Optimizing Communication in Distrib-
uted Virtual Environments by Specialized Protocols .......................... .
R. J. Hubbold, X. Dongbo, S. Gibson: MAV ERIK - The Manchester Virtual Envi-
ronment Interface Kernel ............................................... . 11
A. del Pino: MPSC - A Model of Distributed Virtual Environments 21
T. Axling, S. Haridi, L. Fahlen: Virtual Reality Programming in Oz ............. . 31
C. 1. Breiteneder, S. J. Gibbs, C. Arapis: TELEPORT - An Augmented Reality Tele-
conferencing Environment .............................................. . 41
K. T. Simsarian, 1. Karlgren, L. E. Fahlen, I. Bretan, E. Frecon, T. Axling, N. Frost,
L. Jonsson: Achieving Virtual Presence with a Semi-Autonomous Robot Through a
Multi-Reality and Speech Control Interface ................................. . 50
K. Chung, W. Wang: Quick Elimination of Non-Interference Polytopes in Virtual
Environments ........................................................ . 64
P. WiBkirchen, K. Kansy, G. Schmitgen: Intergrating Graphics into Video Image-
Based Camera Tracking and Filtering ..................................... . 74
P. Astheimer, C. Knopfle: 3D-Morphing and its Application to Virtual Reality ..... . 85
I.-S. Pandzic, T. K. Capin, N. Magnenat Thalmann, D. Thalmann: Motor Functions
94
in the VLNET Body-Centered Networked Virtual Environment ................. .
E. Bouvier, P. Guilloteau: Crowd Simulation in Immersive Space Management .... . 104
M. Usoh, M. Slater, T.1. Vassilev: Collaborative Geometrical Modelling in Immersive
Virtual Environments .................................................. . 111
P. Torguet, F. Rubio, V. Gaildrat, R. Caubet: Multi-User Interactions in the Con-
text of Concurrent Virtual World Modelling ................................ . 121
H. Oyama: System Integration of VR-Simulated Surgical Support System ........ . 131
M. Slater, M. Usoh, S. Benford, D. Snowdon, C. Brown, T. Rodden, G. Smith,
S. Wilbur: Distributed Extensible Virtual Reality Laboratory (DEVRL) .......... . 137
H. Jense, K. Donkers: Dynamic Management of Geographic Data in a Virtual
Environment ......................................................... . 149
J.-F. Balaguer: VRML for LHC Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 159
J. Nomura: Virtual Housing System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 169
Scientific Visualization '96
Volume Rendering
P. Criscione, C. Montani, R. Scateni, R. Scopigno: DiscMC: An Interactive System
for Fast Fitting Isosurfaces on Volume Data ................................. 178
F. Weller, R. Menc1: Nearest Neighbour Search for Visualization Using Arbitrary Tri-
angulation ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 191
VIII
M. Sramek: Fast Ray-Tracing of Rectilinear Volume Data ...................... 201
J. Smit, M. Bosma, J. T. van Scheltinga: Metric Volume Rendering ............... 211
User Interfaces and Scientific Visualization
T. Fruhauf, F. Dai: Scientific Visualization and Virtual Prototyping in the Product
Development Process ................................................... 223
R.-T. Happe, M. Rumpf: Characterizing Global Features of Simulation Data by Selected
Local Icons ........................................................... 234
H. Haase, Ch. Dohrmann: Doing it Right: Psychological Tests to Ensure the Quality of
Scientific Visualization ................................................. 243
Architecture of Scientific Visualization Systems
R. van Liere, J. J. van Wijk: CSE: A Modular Architecture for Computational Steering 257
H. Wright, K. Brodlie, M. Brown: The Dataflow Visualization Pipeline as a Problem
Solving Environment ................................................... 267
D. Hajek, J. Nouza: Unhiding Hidden Markov Models by their Visualization (Applica-
tion in Speech Processing) ..... _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 277
Flow Visualization
W. de Leeuw, F. Post, R. W. Vaatstra: Visualization of Turbulent Flow by Spot Noise 286
R. Grosso, M. Schulz, J. Kraheberger, T. Ertl: Flow Visualization for Multiblock
Multigrid Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 296
Appendix: Colour Figures ............................................... 309
Optimizing Communication in Distributed Virtual
Environments by Specialized Protocols
Dieter Schmalstieg, Michael Gervautz, Peter Stieglecker
Institute of Computer Graphics. Vienna University of Technology
[email protected] -http://www.cg.tuwien.ac.atl
Abstract. A successful implementation of a distributed virtual environment
should be built on a strong network layer. The network as a constrained
resource must be used efficiently, and also the structure of communication
should allow to select those features that are needed without having to
support needlessly complicated protocols. Therefore we designed a set of
specialized protocols tailored for dedicated tasks of communication in
virtual environments. The combination of these protocols yields the desired
communication functions without introducing much overhead. In particular,
it is possible for participants with varying degrees of capability to use the
virtual environment and to communicate with each other.
1 Introduction
The restrictions that are most hard to overcome in distributed virtual environments
are the need for consistency, and constrained network bandwidth. It is because of
these restrictions that virtual environments either focus on rich interaction
[Car193, Snow94, Bric94, Brol95] or on large-scale distribution [Mace94], but not
both.
Our goal is to develop a distributed virtual environment in which users can
participate and contribute content. We favor a client-server based approach, that
lets users run client software and connect to servers over a network [Schm95].
Such a scheme will separate the participants from the providers of the VB
infrastructure. Users can use the VE with inexpensive desktop machines, and do
not have to be responsible for setting up the VE infrastructure. This is important if
a large, loosely coupled user community is to be supported. In particular, the
simulation of the environment is independent of the presence of users - the VB
exists even if no user is currently present. The server provides consistency,
concurrency control and persistence, that are otherwise hard to accomplish.
Scalability is achieved by localizing the simulation: every server is responsible
for a region in the virtual universe, and maintains a loosely coupled connection to
its neighbors. Inside the server's region, the influence of objects is also localized
to a relatively small area of interest.
Simulation kernel. Our virtual environment consists of actors. An object
oriented hierarchy allows diverse actor types representing different levels of
"intelligence". Pure static actors serve as "decoration" of the scene (walls, trees
etc.) and have no built-in behavior. Such actors can be extended to include key
framed, deterministic animation (e.g. a clock with moving hands). A more
sophisticated class of actors exhibits behavior that is formulated in an interpreted
scripting language. Behaviors are triggered by messages that are exchanged
2
between actors. As messages are exchanged, the simulation progresses.
Modifications to the internal state of the actors, in particular their visual
representation, are reflected in the virtual environment. The most powerful actor
type is controlled by an external application.
Multiple levels of participation. The separation of server and clients allows
multiple levels of participation, dependent on the type of client that is used:
An observer can only explore the VE, but cannot interact with any objects.
The client may limit its display to a pure walk-through (only considering static
geometry), or also request the dynamic changes of the visual artifacts, that are
created by the simulation. Nothing an observer does affects the VE.
A participant may introduce his own avatar and use it to fully interact with
the simulation, its ~utonomous agents and other avatars. His actions modify the
dynamic state of the VE; they are distributed to other clients and stored
persistently in the database.
An author may contribute his own content to the virtual environment. He
may create and destroy objects, and even more importantly create new types of
objects with their own behavior, that can continue to exist as autonomous agents
without the user's aid.
This hierarchy of participation is similar to the one found in conventional
MUDs (text-based multi-user games) that can in many respect be seen as YEs
without a visual component.
To maximize flexibility, we also allow applications to function as clients.
While most behaviors of objects in the VE can be formulated using our scripting
engine, the most interesting behaviors are too complex or computationally
demanding for scripts. Therefore an interface is pro'vided to allow external
applications to "remote control" objects in the VE. Because the only restriction
for an application client is that it complies to the network protocols we use, any
application can be made to cooperate with the VE.
Overview of the protocols. The requirements we have for our system are
diverse and demanding. A single unified framework for communication that
incorporates every form of information exchange into a single protocol is not
sufficient. Instead, we define a set of highly specialized protocols that
complement each other and can be tailored for the task.
Protocol Responsible for
Connection login, logout, protocol negotiation, user migration
management:
Avatar control: navigating the user's representation through the VE
Geometry: transmitting geometric description of the objects in the VE to the
client
Animation: transmitting changes in the visual database of the VE to the client
Simulation: exchanging messages concerning the ongoing simulation among
actors and between actor and client
Interaction: letting the user interact with objects in the VE and other users
Authoring: managing modifications to the structure of the VE, such as object
instantiation and deletion, creation of new object types and
configuration of external applications
Table 1. Overview and characterization of the protocol framework
