SIMNET was perhaps the world's first fully operational virtual reality system[1] and was the first real time, networked simulator.
Jack Thorpe of the Defense Advanced Research Projects Agency (DARPA) saw the need for networked multi-user simulation.
Being able to simulate certain combat scenarios, and to have participants remotely located rather than all in one place, hugely reduced the cost of training and the risk of personal injury.
[3] Long-haul networking for SIMNET was run originally across multiple 56 kbit/s dial-up lines, using parallel processors to compress packets over the data links.
SIMNET was developed by three companies: Delta Graphics, Inc.; Perceptronics, Inc.; and Bolt, Beranek and Newman (BBN), Inc.
The fidelity of the simulation was such that it could be used to train for mission scenarios and tactical rehearsals for operations performed during the U.S. actions in Desert Storm in 1992.
Duncan (Duke) Miller, the BBN SIMNET program manager, first used this term, which harks back to the earliest days of ship navigation, to explain how simulators were able to communicate state change information to each other while minimizing network traffic.
[6] In addition to the network, the second fundamental challenge at the time SIMNET was conceived was the inability of graphics systems to handle large numbers of moving models.
For example, most contemporary flight simulators used binary space partitioning which is computationally effective for fixed environments since polygon display order (i.e., their depth coherence) can be pre-computed.
In contrast, Z-buffer techniques do not depend on pre-computed depth coherence and were therefore a key enabling technology for SIMNET's on-ground point of view and large numbers of moving vehicles.
Z-buffering is memory intensive relative to Binary Space Partitioning but was made possible in part because the cost of RAM at the time had dropped significantly in price.