Introduction to DIVE
Introduction to DIVE
The SICS Distributed Interactive Virtual Environment (DIVE) is an experimental platform for the development of virtual environments, user interfaces and applications based on shared 3D synthetic environments. Dive is especially tuned to multi-user applications, where several networked participants interact over an internet.
Dive is based on a peer-to-peer approach with no centralized server, where peers communicate by reliable and non-reliable multicast, based on IP multicast. Conceptually, the shared state can be seen as a memory shared over a network where a set of processes interact by making concurrent accesses to the memory.
Consistency and concurrency control of common data (objects) is achieved by active replication and reliable multicast protocols. That is, objects are replicated at several nodes where the replica is kept consistent by being continuously updated. Update messages are sent by multicast so that all nodes perform the same sequence of updates.
The peer-to-peer approach without a centralized server means that as long as any peer is active within a world, the world along with its objects remains "alive". Since objects are fully replicated (not approximated) at other nodes, they are independent of any one process and can exist independently of the creator.
The dynamic behaviour of objects may be described by interpretative scripts in Dive/Tcl that can be evaluated on any node where the object is replicated. A script is typically triggered by events in the system, such as user interaction signals, timers, collisions, etc.
Users navigate in 3D space and see, meet and collaborate with other users and applications in the environment. A participant in a Dive world is called an actor, and is either a human user or an automated application process. An actor is represented by a "body-icon" (or avatar), to facilitate the recognition and awareness of ongoing activities. The body-icon may be used as a template on which the actor's input devices are graphically modeled in 3D space.
A user `sees' a world through a rendering application called a visualizer (the default is currently called Vishnu). The visualizer renders a scene from the viewpoint of the actor's eye. Changing the position of the eye, or changing the "eye" to an another object, will change the viewpoint. A visualizer can be set up to accommodate a wide range of I/O devices such as an HMD, wands, datagloves, etc. Further, it reads the user's input devices and maps the physical actions taken by the user to logical actions in the Dive system. This includes navigation in 3D space, clicking on objects and grabbing objects etc.
In a typical Dive world, a number of actors leave and enter worlds dynamically. Additionally, any number of application process (applications) exist within a world. Such applications typically build their user interfaces by creating and introducing necessary graphical objects. Thereafter, they "listen" to events in the world, so that when an event occurs, the application reacts according to some control logic.
The software is a research prototype and is therefore provided on an `as is' basis with no provisions for support or future enhancements.
The Dive architecture is described in:
Primary contacts for
the Dive software