Sharing Viewpoints in Collaborative Virtual Environments

1
Sharing Viewpoints in Collaborative Virtual
Environments
Steven Valin A thesis submitted to the Graduate
School - New Brunswick Rutgers, The State
University of New Jersey in partial fulfillment
of the requirements for the degree of Master of
Science Graduate Program in Electrical and
Computer Engineering and written under the
direction of Professor Ivan Marsic. May 1, 2000
2
Abstract
This thesis explores to what degree shared
viewpoints in three-dimensional collaborative
virtual environments enable effective
collaboration. A lightweight Java-based tool for
creating collaborative virtual environments was
developed and used in the study. A series of
experiments were conducted to assess the
effectiveness of shared viewpoints on two simple
tasks. Control groups were provided with
telepointers. Experimental groups were provided
with telepointers and shared views. The results
indicate that for participants with access to
both tools, shared views are preferred over
telepointers for tasks involving joint
exploration of the environment or some object of
common interest.
3
Preview

• Thesis objectives
• Related Work
• cWorld System
• Experiment
• Results
• Conclusions
• Future Work

4
Thesis Objectives

• The goal of this research is two-fold
• To develop a lightweight, Java-based tool for
  enabling multi-user, synchronous collaboration in
  a 3D virtual environment.
• To investigate the degree to which shared
  viewpoints help enable effective collaboration in
  3D virtual environments.

In this thesis we describe the system we have
implemented and the experiments we have performed
to assess user preference for single, shared
viewpoints over multiple independent viewpoints
when performing synchronous, collaborative tasks
in a 3D virtual environment.
5
Related Work

• Much work has focused on developing the VR
  metaphor to the point where it attempts to
  completely mimic collaboration in real
  environments 3,4,6,8
• MASSIVE, DIVE, VLNET
• Much attention has been paid to user embodiment
  2,4,7,21
• Issues related to user embodiment, such as facial
  expression and involuntary movement, require
  expensive VR software and hardware
• User embodiment and complete immersion in virtual
  worlds may not be necessary for a variety of
  collaborative tasks that can be performed in 3D
  virtual environments
• In fact, much success has been reported in
  enabling effective collaboration where
  participation in the collaboration required
  little more than a PC and a network connection

6
Related WorkTheatre in the Mill study 18

• Collaborative theatre set design using a 3D VRML
  model of the Theatre in the Mill
• Collaborative design was accomplished by passing
  stewardship of the model among team members
• System was designed to enable collaborative set
  design, not immersive rehearsal
• Authors point out that while such an option might
  be desirable, it was deemed far too expensive for
  most theatre groups
• 3D model was designed to make sure that the
  limited time in the actual Mill Theatre was used
  effectively (i.e., for rehearsal and performances
  rather than set design and redesign)

7
Related WorkTheatre in the Mill study

• The study reported that the use of the VRML model
  proved extremely valuable to traveling theater
  companies
• Set designers were able to view the performance
  space and try out ideas before committing to
  physical construction
• Performers were able to familiarize themselves
  with the sets beforehand
• However, there were some shortcomings with the
  model
• Relatively simple interactions supported by
  VRMLScript could not support large scale movement
  of lighting rigs and scenery redesign, often
  requiring a VRML developer to modify the model
• Users had to take turns editing the model due to
  lack of support for synchronous collaboration
  among multiple users

8
Related WorkMultiple Target Video study 9

• Researcher sought to understand the issues
  related to enabling effective collaboration among
  multiple users in media spaces
• Researchers discovered that while their system
  enabled subjects to collaborate successfully on
  two tasks involving remote artifacts, many
  limitations were uncovered
• First, despite the use of four cameras per
  office, the views provided were still not optimal
  for the given tasks
• Second, the different views provided by the
  cameras caused problems in relating different
  scenes to one another
• Third, the system hindered the ability to direct
  the attention of remote partners, interfering
  with the establishment of a mutual orientation to
  relevant objects. The authors point out that the
  subjects seemed to want control over their
  partners views

9
Related WorkEstablishing Mutual Orientation in
Virtual Environments study 12

• Repeated basically the same experiments as in the
  MTV study, but this time in a collaborative 3D
  virtual environment
• Explored the extent to which their system
  provided participants with the ability to refer
  to and discuss features of the virtual
  environment
• Found problems due to fragmented views of
  embodiments in relation to shared objects, caused
  in part by limited field-of-view (55o)
• Observed difficulties experienced by participants
  in understanding others perspectives
• Participants had great difficulty in
  understanding what others could see and expressed
  a desire for being in the others position
• Authors proposed improved representations of
  others actions and adoption of a form of
  target-based navigation that would provide users
  with shortcuts for orienting towards targets

10
Our Approach

• In order to address the issue of being in the
  others position, we propose the use of shared
  viewpoints - a form of guided navigation that
  allows one or more users to attach their
  viewpoints to another users viewpoint
• Once attached to a shared viewpoint, any
  participant may then transform that viewpoint
• Provides a form of strict WYSIWIS 22 in 3D CVEs
  when needed
• Guided navigation has been explored in 25. Our
  approach differs in several ways
• Users in cWorld are not arranged in a hierarchy.
  Once users agree to share viewpoints, anyone can
  take the lead
• Once in a shared viewpoint everyone sees exactly
  the same thing, while in 25 users are pulled
  along in the direction of the guides movement
• Attachment to the shared viewpoint is a form of
  target-based navigation as in 12
• When user accepts invitation to join a shared
  viewpoint, his/her own viewpoint is immediately
  transformed to be the same as the viewpoint of
  the user that sent the invitation

11
cWorld SystemBackground and Related Work
Distributed virtual reality systems may be
classified by how the data is exchanged between
machines participating in the session

• Centralized Systems
• Use Client-Server paradigm
• Require powerful server
• Suffer from scalability problems that introduce
  latency
• Community Place 15 and Active Worlds System 1
• Distributed Systems
• Eliminate server process
• Peer-to-Peer communication using multicast
  networking
• DIVE 5 and MASSIVE-2 11

12
cWorld SystemBackground and Related Work

• Since the creation of VRML 1.0, there has been
  much interest in using VRML to create multi-user,
  shared virtual worlds
• Current VRML standard does not offer any
  constructs for direct multi-user support
• Recent work has focused on adding support for
  shared virtual worlds
• VIRTUS 19, ToolSpace 10, and 5
• Basic approach is to add proprietary extensions
  to VRML and a Java layer to enable multi-user,
  synchronous collaboration

13
cWorld System Our Approach

• 100 pure Java
• cWorld is developed as a Java Bean that uses the
  Java3D to provide 3D graphics authoring and is
  plugged into the DISCIPLE collaboration bus in
  order to enable multi-user, synchronous
  collaboration
• Overcomes the limitations of VRML, while at the
  same time supports the use of VRML objects
• 100 Pure Java means code portability without
  special plug-ins and easy integration with other
  Java APIs, such as JTAPI and Java Speech

14
cWorld System Java3D API

• Part of the Java Media family of APIs
• Java 2D, Java 3D, Java Speech, Java Telephony
• Java3D API is an application programming
  interface used for writing stand-alone
  three-dimensional graphics applications or
  web-based applets
• Provides several basic classes used to construct
  and manipulate a scene graph, and to control
  viewing and rendering
• Scene graph contains a complete description of
  the entire scene, or virtual universe, including
  geometric data, attribute information, and the
  viewing information needed to render the scene
  from a particular view

15
cWorld System Java3D Scene Graph
16
cWorld System Java Beans API

• Java Beans API defines a software component model
  for Java
• Three most important features of a Java Bean
• Properties that it exposes
• Named attributes associated with a bean that can
  be read or written by calling appropriate methods
• Methods it allows other components to call
• Just normal Java methods that can be called from
  other components
• Events it fires
• A mechanism for propagating state change
  notifications between a source object and one or
  more listener objects
• Simplest kind of bean nothing more than a Java
  class that follows fairly strict naming
  conventions for its event listeners and its
  methods

17
cWorld System DISCIPLE

• Mixture of Client-Server and Peer-to-Peer
  architecture
• Each user runs a copy of the collaboration client
  and each client contains a copy of the
  applications (Java components) that are the foci
  of the collaboration
• All copies of replicated applications are kept in
  synchrony and activities occurring on any one of
  them are reflected on the other copies
• Set of participants is represented hierarchically
  as an Organization, and they meet in Places.
• Organizations and Places are abstractions
  implemented as multicast groups

18
cWorld System DISCIPLE

• DISCIPLE workspace is a shared container where
  Java Beans can be loaded very much like Java
  Applets downloaded to the web browser, with the
  addition of group sharing
• Collaborators import beans by drag-and-drop
  manipulation into the workspace
• The imported bean becomes a part of a multi-user
  application and all participants can interact
  with it

19
cWorld System DISCIPLE High-Level Architecture
20
cWorld System Event Interception and Symmetric
Distribution in DISCIPLE
Event generated in local bean is (instead of
being delivered to local listener) is (1)
intercepted by the event adapter and (2) sent to
the collaboration bus. The bus multicasts the
event to all the shared beans (remote and local)
(3). Each event adapter receives the multicast
event and delivers it to all listeners (4)
21
cWorld System DISCIPLE Multi-Document Editor
Framework
22
cWorld System cWorld Class Hierarchies and
Relationships
23
cWorld System cWorld Bean

• Enables synchronous, collaborative, multi-user
  authoring of 3D collaborative virtual
  environments
• Built as a Java Bean
• Uses DISCIPLE MDE Framework to provide
  synchronous collaboration
• Provides a graphical user interface to the Java3D
  API
• Uses Java2 SDK v1.3.0 RC1 and the Java3D 1.2 Beta
  API OpenGL implementation
• Does not require any special hardware and can be
  operated using the keyboard and PC mouse
• Also supports the use of the Magellan SPACE Mouse
  to provide a more natural six-degrees of freedom
  of movement for navigating the 3D space

24
cWorld System cWorld Interfaces and Functionality

• cWorld provides support for adding and removing
  primitive objects such as cubes, spheres, and
  cones
• Once objects are added to scene, they may be
  translated, rotated, and stretched
• Through the use of a property editor, object
  properties such as color, shininess, highlight
  color, and texture mappings may be edited
• Support for ambient lights, point lights,
  directional lights, and spot lights
• Support for VRML objects
• Telepointers
• Shared Viewpoints

25
cWorld System Primitive 3D Objects

• The following simple geometries are supported in
  cWorld
• Spheres
• Cylinders
• Cones
• Cubes
• Objects are added to the scene by a simple
  point-and-click operation with the PC mouse
• Objects may be translated, rotated, and stretched
• Appearances such as material color, shininess,
  and texture mappings may be edited

26
cWorld System Lights

• cWorld supports
• Ambient Lights
• Point Lights
• Directional Lights
• Spot Lights
• Location of light is indicated through the use of
  a mnemonic device
• Mnemonic device appears as a wire-frame primitive
  object whose color indicates the color of the
  light
• Manipulating the orientation of the mnemonic
  device sets the direction of the light
• Light properties such as color and attenuation
  may be edited

27
cWorld System Property Editor
28
cWorld System VRML Objects
29
cWorld System Example CVE Created Using cWorld
30
cWorld System Telepointers

• When invoked, a 3D arrow is drawn from the
  position and orientation of the users viewpoint

31
cWorld System Shared Views

• A form of both target-based navigation and
  guided navigation

32
Experiment

• Purpose
• To evaluate the effectiveness of shared
  viewpoints in accomplishing collaborative tasks
  in 3D virtual environments
• Participants
• 30 participants ranging in age from 18 to 34,
  with varying levels of experience with computers
  and video games
• Divided into two groups (Experimental group and
  Control group). Further subdivided into teams of
  three participants.
• Control group teams were provided with
  telepointers. Experimental group teams were
  provided with telepointers and shared views
• Procedure
• Task 1 - Room Orientation Task
• Task 2 - Room Design Task
• Task 3 - Whats different with this room? Task

33
ExperimentTask 1 - Room Orientation Task

• The primary purpose of this task was to
  familiarize participants with the Magellan SPACE
  Mouse and the cWorld interfaces.
• The task is as follows
• Each subject is seated at a workstation where a
  cWorld session has been started.
• A research team member instructs participants in
  the use of cWorld and the Magellan SPACE Mouse.
  This training includes moving in the environment,
  adding and moving objects, using telepointers,
  and using shared viewpoints (experimental group
  only).
• Next, the researcher instructs each participant
  to place a furniture object at a particular
  location.
• After all participants have placed their object,
  they are instructed to each take turns indicating
  to the other participants which object they
  placed using the telepointers and shared
  viewpoints (experimental group only).

34
ExperimentTask 2 - Room Design Task

• This task was designed to evaluate the degree to
  which shared viewpoints may enable effective
  collaboration in a 3D environment.
• The task is as follows
• Three participants enter a cWorld space that
  contains an empty (virtual) office.
• Each participant is instructed to imagine that
  they will all be moving into a shared office.
  They each have a desk, a cabinet, and a bookcase
  that they wish to move with them. They are
  instructed to use cWorld as a tool to decide
  where they would like to have the moving company
  place their furniture when it is moved to their
  new office.
• Each participant is given their own set of
  (virtual) office furniture that they are asked to
  place in the room however they wish, without
  breaking certain rules e.g., furniture cannot
  block doors or windows, desks may not be stacked
  on top of one another, etc.

35
ExperimentTask 2 - Room Design Task

• The task was made more difficult by the fact the
  furniture fits into the room in only a limited
  number of configurations.
• Thus, in order to accomplish the task, all users
  must participate (they have their own furniture
  to place) and all users must collaborate (since
  it is unlikely that all of the furniture will fit
  into the room on the first try).
• There are also competitive components in task 2
• Users should want to place their own furniture in
  prime locations (e.g., next to the window or away
  form the door), and
• they may want to finish first.

36
ExperimentTask 3 - Whats different with this
room? Task

• The purpose of Task 3 was to compare the results
  of task 2 with a task that appeared to be more
  collaborative in nature and less competitive.
• The task is as follows
• Participants are placed in a cWorld environment
  that contains two rooms separated by a doorway.
  The two rooms are almost identical except for
  some minor differences in the way the furniture
  was placed. One room is designated the model
  room and the other is designated the working
  room.
• Participants are asked to identify and correct
  the differences in the working room so that it
  exactly resembled the model room.
• In order to insure that the participants
  collaborate (and do not just immediately correct
  the imperfections that they themselves only see),
  we instruct them to get agreement from the other
  subjects before making any changes to the working
  room.

37
ExperimentTask 3 - Difference 1
Model Room
Working Room
38
ExperimentTask 3 - Difference 2
Model Room
Working Room
39
ExperimentTask 3 - Difference 3
Model Room
Working Room
40
ResultsTask 2
41
ResultsTask 3
42
ResultsSelected participants opinions on the
usefulness of shared viewpoints
43
ResultsSelected participants opinions on the
usefulness of telepointers
44
Conclusions

• Sharing viewpoints helps enable effective
  collaboration in 3D virtual environments
• Shared viewpoints are preferred over telepointers
  for tasks involving joint exploration of virtual
  environments and objects of common interest
• Participants in collaborative 3D virtual
  environments desire at least some form of
  peripheral monitoring of co-collaborators
• Java3D and the DISCIPLE framework provided an
  easy-to-use, scalable, efficient means for
  enabling synchronous, multi-user collaboration in
  three-dimensional collaborative virtual
  environments

45
Future Work

• Adding support in cWorld for persistent avatars.
  
• Users should be able to create their own avatars
  using the cWorld toolset, and then have their
  avatar attached to their viewing platform. Future
  experiments could explore whether it is necessary
  to provide pseudo-humanoid avatars, or whether
  something as simple as a hand or a pointed-finger
  may suffice.
• Investigation into the use of 2D maps and radar
  views for supporting peripheral awareness of
  co-collaborator activities.
• Adding support for smooth attachment to and
  detachment from shared viewpoints.
• Integrating functionality provided by other Java
  Media APIs.
• For instance, the Java Speech API could provide
  voice command functionality for navigating the
  cWorld environment and manipulating objects.
  Also, telephony applications could be integrated
  using the Java Telephony API.

46
References

• 1. Active Worlds. Corporate web page
  http//activeworlds.com.
• 2. Benford, S., Bowers, J., Fahlen, L. E.,
  Greenhalgh, C., and Snowdon, D. User embodiment
  in collaborative virtual environments. In CHI 95
  Proceedings, ACM Press, pp.242-249, 1995.
• 3. Benford S., and Greenhalgh, C. MASSIVE A
  collaborative virtual environment for
  teleconferencing. ACM Transactions on
  Computer-Human Interaction, 2(3)239-261,
  September 1995.
• 4. Capin, T. K., Pandzic, I. S., Thalmann, D.,
  and Thalmann, N. M. Realistic avatars and
  autonomous virtual humans in VLNET networked
  virtual environments. Virtual Worlds on the
  Internet, J. Vince and R. Earnshaw, eds., IEEE
  Computer Society, Los Alamitos, pp.157-173, 1998.
• 5. Carson, J. and Clark, A. Multicast Shared
  Virtual Worlds Using VRML97. In Proceedings of
  the 4th Symposium on the Virtual Reality Modeling
  Language (VRML99), Paderborn, Germany, pp.
  133-140, 1999.
• 6. Carlsson, C., and Hagsand, O. DIVE a
  multi-user virtual reality system. In IEEE
  Virtual Reality Annual Symposium, pp. 394 400,
  1993.
• 7. Era, T., Kauppinen, K., Kivimäki, A., and
  Robinson, M. Producing identity in collaborative
  virtual environments. In Proceeding of the ACM
  Symposium on Virtual Reality Software and
  Technology (VRST98), Taipei, Taiwan, pp. 35-42,
  November 1998.

47
References

• 8. Frécon, E., and Nöu, A. A. Building
  distributed virtual environments to support
  collaborative work. In Proceeding of the ACM
  Symposium on Virtual Reality Software and
  Technology (VRST98), Taipei, Taiwan, pp.105-113,
  November 1998.
• 9. Gaver, W., Sellen, A., Heath, C., and Luff,
  P. One is not enough Multiple views in a media
  space. In Proceedings of INTERCHI 93, ACM, New
  York, pp.335-341, April 1993.
• 10. Goddard, T., and Sunderam, V. S. ToolSpace
  Web based 3D collaboration. In Proceedings of the
  4th Symposium on the Virtual Reality Modeling
  Language (VRML99), Paderborn, Germany,
  pp.161-165, 1999.
• 11. Greenhalgh, C. Dynamic, embodied multicast
  groups in MASSIVE-2. Technical Report
  NOTTCS-TR-96-8, Technical Report Department of
  Computer Science, The University of Nottingham,
  1996.
• 12. Hindmarsh, J., Fraser, M., Heath, C.,
  Benford, S., and Greenhalagh, C. Fragmented
  interaction Establishing mutual orientation in
  virtual environments. In Proceedings of the ACM
  1998 Conference on Computer-Supported Cooperative
  Work (CSCW'98), Seattle, WA, pp.217-226, November
  1998.
• 13. IBM Theatre Projects, http//www.ibm.com/sfas
  p/theatre.htm
• 14. Krasner, G., Pope, S. A Cookbook for Using
  the Model-View-Controller User Interface Paradigm
  in Smalltalk-80. Journal of Object-Oriented
  Programming, 1(3)26-49, August/September 1988.

48
References

• 15. Lea, R., Honda, Y., Matsuda, K., and
  Matsuda, S. Community place Architecture and
  performance. In Proceedings of VRML 97, 1997.
• 16. LogiCad3D GmbH, Magellan/SPACE Mouse,
  http//www.logicad3d.com
• 17. Luff, P., Heath, C., and Greatbatch, D.
  Tasks-in-interaction Paper and screen based
  doumentation in collaborative activity. In
  Proceedings of the ACM 1992 Conference on
  Computer-Supported Cooperative Work (CSCW'92),
  Toronto, Canada, pp. 163-170, 1992.
• 18. Palmer, I. J., and Reeve, C. M.
  Collaborative theatre set design across networks.
  In Virtual Worlds on the Internet, J. Vince and
  R. Earnshaw, eds., IEEE Computer Society, Los
  Alamitos, pp.253-261, 1998.
• 19. Saar, K. VIRTUS A Collaborative Multi-User
  Platform. In Proceedings of the 4th Symposium on
  the Virtual Reality Modeling Language (VRML99),
  Paderborn, Germany, pp.141-152, 1999.
• 20. Singhal, S., and Zyda, M. Networked Virtual
  Environments Design and Implementation. Addison
  Wesley, New York, 1999.
• 21. Snowdon, D., and Tromp, J. Virtual body
  language Providing appropriate user interfaces
  in collaborative virtual environments. In
  Proceedings of the ACM Symposium on Virtual
  Reality Software and Technology (VRST97),
  pp.37-44, 1997.

49
References

• 22. Stefik, M., Bobrow, D. G., Lanning, S., and
  Tatar, D. WYSIWIS revised Early experiences
  with multiuser interfaces. ACM Transactions on
  Information Systems, 5(2)147-167, April 1987.
• 23. Sun Microsystems, Inc. JavaBeans API
  Specification, http//java.sun.com/beans/
• 24. Wang, W., Dorohonceanu, B., and Marsic, I.
  Design of the DISCIPLE synchronous collaboration
  framework. In Proc. of the 3rd IASTED
  International Conference on Internet, Multimedia
  Systems and Applications, Nassau, The Bahamas,
  pp.316-324, October 1999.
• 25. Wernert, E., and Hanson, A. A framework for
  assisted exploration with collaboration. In
  Proceedings of IEEE Visualization99, San
  Francisco, October 1999