Abstract:

In most distance learning systems, students typically use an online web interface to browse educational material. However, for a better exposure to the concepts under study, students must have access to a truly interactive environment that allows virtual manipulation of 3D objects that represent and symbolize those concepts. The Institute for Advanced Education in Geospatial Sciences (IAEGS), as part of its goals, has developed an online curriculum of GIS and Remote Sensing courses. In order to deliver this content as efficiently as possible, IAEGS has created the Virtual Portal, a client-server application that integrates virtual worlds and multimedia content with interactive educational material delivered on the web. In order to allow interaction among users of a virtual world, a remote server is required to keep track of each user state at real time. Since the remote server is based on a centralized approach, the server may eventually become the bottleneck in this perennial client-server communication cycle. Therefore, for the effective handling of client-server messages, an elegant message protocol must be implemented. The protocol should define smart data structures to relax bandwidth constraints and allow for future growth and scalability. It must also implement synchronization methods to avoid message bursting and reduce the burden on the server. This paper discusses a message protocol whose overall goal is to optimize the network usage of multi-client 3D sessions that take place in the Virtual Portal client-server application.