A middleware approach to building large-scale open shared virtual worlds

With the tremendous success of the Internet, multi-participant real time applications based on a shared "virtual world" paradigm are bound to develop at a fast pace: multi-user online games, virtual shopping malls, concurrent design applications, etc. These applications attempt to give end users the illusion of being immersed in a conceptually unique shared virtual environment where they can interact in, real time with other users or computer-controlled entities. The critical point is to provide a consistent view of the world to all participants. Classical client-server approaches work well for a limited number of users on a local network, but fail when trying to support large scale shared virtual worlds with a large number of users on an open network with uncontrolled resources like the Internet. The paper presents the Continuum platform which aims to offer a software oriented framework for 3D shared worlds, based on a shared object replication model and a set of interfaces describing services. The paper identifies the requirements of such a platform and shows how the architecture of Continuum tries to answer these requirements. Focus is put on the end user application programmer point of view. An example application illustrates how the framework can be used and specialized.