"Models for
design, implementation and deployment of 3D Collaborative
Virtual Environments"
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This work aims at
providing some cues in order to address the essential
requirements about the design of 3D Collaborative Virtual
Environments (CVE).
We have identified six essential topics that must be addressed
when designing a CVE.
For each of them, we present a state of the art about the
solutions that can address this topic, then we show our own
contributions: how we improve existing solutions and what are
our new propositions.
1 - Choosing a model for the distribution of a CVE
We need a distribution
model to distribute as efficiently as possible the content of a
CVE among all the nodes involved in its execution, including the
machines of the distant users.
Our proposition is to
allow CVE designers to mix in a same CVE the three main
distribution models usually encountered: centralized on a
server, totally replicated on each site, or distributed
according to a hybrid distribution model.
2 - Choosing a model for the synchronization of these nodes
To maintain
consistency between all the nodes involved in the execution of a
CVE, we must choose between a strong synchronization or a
relaxed one, or an in-between solution.
Our proposition is to manage some temporary relaxation of the
synchronization due to network breakdowns, with several
synchronization groups of users, making them aware of these
network breakdowns, and to allow some shared objects to migrate
from one site to another.
3 - Adapting the Virtual Environment to various hardware
systems
VR applications must
be adapted to the software and to the hardware input and output
devices that are available at run-time, in order to be able to
deploy a CVE onto di fferent kinds of hardware and software.
Our solution is the PAC-C3D software architectural model which
is able to deal with the three main distribution modes
encountered in CVE.
4 - Designing interaction and collaboration in the VE
Expressing the
interactive and collaborative capabilities of the content of a
CVE goes one step beyond geometric modeling, by adding
interactive and collaborative features to virtual objects.
We propose a unified model of dialog between interactive objects
and interaction tools, with an extension to Collada in order to
describe interactive and collaborative properties of these
interactive objects and interaction tools.
5 - Choosing the best metaphors for collaborative
interactions
Most of the time single-user interaction tools and metaphors are
not adapted to off er efficient collaboration between users of
a CVE.
We adapt some of these tools and metaphors to collaborative
interactions, and we propose new really collaborative metaphors
to enhance real multi-user collaborative interactions, with
dedicated collaborative feedback.
6 - Embedding the users' physical workspaces within the CVE
Taking into account
users' physical workspaces makes it possible to adapt a CVE to
the hardware input and output devices of the users, and to make
them aware of their physical limitations and of those of the
other users, for better interaction and collaboration.
We propose the Immersive Interactive Virtual Cabin (IIVC)
concept to embed such 3D representations in CVE.