Collaborative Learning through Flexible Web CVE - Teaching through Multi-User Virtual Environments - page 486

Figure 6. A scene from Learning@Europe, an educational application for European schools

• Client side. The “world engine” is the cli-

ent-side of the application. Through a
number of modules, it manages the con-
nection with the server and controls the
rendering on the client machine. The “in-
teraction engine”, in particular, controls
the collaboration features, while “world
builder” renders in real time the scene, ac-
cording with the shared state of all the ob-
jects and avatars.

example, of positions, rotations and
“state” in general of all the avatars
and objects. Any change of the shared
state is detected and send to all the
clients, raising an “onSync” signal.

• Back End. It consists of a set of tools that

allow the “sessions architects” to configure
and fine tune all the session parameters.

In order to deploy the application, any Web
server (such as IIS or TomCat) can be used; the
Communication Server, instead, is a dedicated
server managing the interaction between each
client and the server. The communication server,
in particular, for each shared object maintains
several versions: one “ remote shared object ”
preserving the state on the communication server;
many “ local shared objects ” (one for each client)
being updated locally. Whenever one interactive
element of a client changes one or more of its
properties, its corresponding local shared object

• Server Side:

◦ Contents Repositories: they store all

the geometries and the textures, cre-
ated at design time.

◦ XML files repository: it stores all the

different configuration (XML) files.
When a client starts a session, the
system selects the right XML file and
loads it.

◦ Communication Server: it keeps the

actual shared state, keeping track, for