Networked Virtual Worlds

Networked multiplayer worlds are typically comprised of users distributed across geographic boundaries all seeing each other simultaneously in a common virtual world. The environment constituents are connected by local area networks (LANs) and wide area networks (WANs). The realism of the virtual world in part depends on the ability of these network connections to communicate the state of the world in real-time. Real-time means that any player must see the state change of another player in less than some predetermined time. This latency between communications should be less than 100 milliseconds in the distributed interactive simulation (DIS) world.

Further realism is provided by visualization of the virtual world as close to reality as possible. Today's technology provides realism by drawing photographic-realistic images on polygonal models rapidly enough to imitate the real world. The frame rate of the virtual world depiction needs to occur at greater than 15 frames a second (60 frames a second is best) on your computer monitor to provide realism.

Synchronization of the distributed virtual worlds must occur frequently and with precision if all the participants are to be assured of accurate virtual world interactions:

• Entities simulated by one computer are visualized on another one.
• Entity information travels as Entity State Protocol Data Units and not as graphical information.
• Synchronization of terrain database and entity models is required for correlation of virtual worlds.
• Latency tolerance must not exceed 100 milliseconds to maintain real-time appearance.
• Hundreds or thousands of entities must be simultaneously synchronized.
• Entity visualization must account for large numbers of moving models in a given field of view.
• The network can be a LAN, WAN, intranet, or the Internet.