SIMNET
Encyclopedia
SIMNET was a wide area network
with vehicle simulators and displays for real-time distributed combat simulation: tanks, helicopters and airplanes in a virtual battlefield. SIMNET was developed for and used by the United States military. SIMNET development began in the mid-1980s, was fielded starting in 1987, and was used for training until successor programs came online well into the 1990s.
(DARPA) saw the need for networked multi-user simulation
. Interactive simulation equipment was very expensive, and reproducing training facilities was likewise expensive and time consuming. In the early 1980s, DARPA decided to create a prototype
research system to investigate the feasibility of creating a real-time distributed simulator for combat simulation. SIMNET, the resulting application, was to prove both the feasibility and effectiveness of such a project (Pimental and Blau 1994).
Training using actual equipment was extremely expensive and dangerous. 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 (Rheingold 1992). 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. This traffic contained not only the vehicle data but also compressed voice.
and aircraft
control simulators, and they were configured to simulate actual conditions within the actual combat vehicle. The tank simulators, for example, could accommodate a full four-person crew complement to enhance the effectiveness of the training. The network was designed to support up to several hundred users at once. 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 (Robinett 1994).
The system used the concept of “dead reckoning
” to collect the positions of the objects and actors within the simulated environment. Essentially this approach proposes that the current position of an object can be calculated from its previous position and velocity (which is composed of vector and speed elements) (Pimental and Blau 1994). Its use in the Gulf War demonstrates the success of the SIMNET, and its legacy was viewed as proof that realtime interactive networked cooperative virtual simulation is possible for a large user population.
Later, the Terrestrial Wideband Network (a high speed descendant of the ARPANET
that ran at T1
speeds) was used to carry traffic. This network remained under DARPA after the rest of ARPANET was merged with NSFNet
and the ARPANET was decommissioned (Rheingold 1992).
which is computationally effective for fixed environments since polygon display order (i.e., their depth coherence) can be pre-computed. While suitable for flight simulators, which largely have a point of view above the Earth's fixed surface, this technique is ineffective near the ground, where the order in which polygons overlay each other changes with the location of the point of view. It is also ineffective with a large number of moving models, since moving a model changes its depth coherence relative to the polygons representing the ground.
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.
SIMNET used Z-buffer displays developed by Delta Graphics. Delta Graphics was founded by Drew Johnston (SW development), Mike Cyrus (President), both from the Boeing Aerospace Company/Graphics Lab, and Jay Beck (CTO and VP), a 3D graphics consultant of Softtool Consulting. The graphics processor, the GDP, custom developed for SIMNET by Gary Wilson (Sr HW Engineer), won out over existing Silicon Graphics HW because of its low cost and because its architecture. It was the first simulator display processor to use a frame buffer and Z-buffer algorithms on a per display channel basis to show the simulated view.
, Fort Rucker
, and Fort Knox
. Additional temporary and permanent locations were in Fort Leavenworth
and Grafenwoehr, Germany.
; the primary U.S. Army follow-on program was the Close Combat Tactical Trainer (CCTT).
The SIMNET-D (Developmental) program used simulation systems developed in the SIMNET program to perform experiments in weapon systems, concepts, and tactics. It became the Advanced Simulation Technology Demonstration (ADST) program. It fostered the creation of the Battle Labs across the US Army, including the Mounted Warfare TestBed
at Ft Knox, Ky, the Soldier Battle Lab at Ft Benning, GA, the Air Maneuver Battle Lab at Ft Rucker, AL, the Fires Battle Lab at Ft Sill, OK.
Additional research programs after the end of SIMNET included work in weather and real-time terrain modifications.
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
with vehicle simulators and displays for real-time distributed combat simulation: tanks, helicopters and airplanes in a virtual battlefield. SIMNET was developed for and used by the United States military. SIMNET development began in the mid-1980s, was fielded starting in 1987, and was used for training until successor programs came online well into the 1990s.
Origination and Purpose
Jack Thorpe of the Defense Advanced Research Projects AgencyDefense Advanced Research Projects Agency
The Defense Advanced Research Projects Agency is an agency of the United States Department of Defense responsible for the development of new technology for use by the military...
(DARPA) saw the need for networked multi-user simulation
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....
. Interactive simulation equipment was very expensive, and reproducing training facilities was likewise expensive and time consuming. In the early 1980s, DARPA decided to create a prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
research system to investigate the feasibility of creating a real-time distributed simulator for combat simulation. SIMNET, the resulting application, was to prove both the feasibility and effectiveness of such a project (Pimental and Blau 1994).
Training using actual equipment was extremely expensive and dangerous. Being able to simulate certain combat
Combat
Combat, or fighting, is a purposeful violent conflict meant to establish dominance over the opposition, or to terminate the opposition forever, or drive the opposition away from a location where it is not wanted or needed....
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 (Rheingold 1992). 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. This traffic contained not only the vehicle data but also compressed voice.
Companies who Developed SIMNET
SIMNET was developed by three companies: Delta Graphics, Inc.; Perceptronics, Inc.; and Bolt, Beranek and Newman (BBN), Inc. There was no prime contractor on SIMNET; independent contracts were let directly to each of these three companies. BBN developed the vehicle simulation and network software, as well as other software such as artillery, resupply, and semi-automated forces often used for opposing forces. Delta Graphics, based in Bellevue, Washington, developed the graphics system and terrain databases. Delta Graphics was eventually bought by BBN. Perceptronics, based in Los Angeles, was responsible for the actual SIMNET simulators; the company's engineers, human factors personnel and manufacturing team designed, developed and built over 300 full-crew simulators, integrating the controls, sound systems and visual systems into the special simulator shells; they also installed the simulators in a number of facilities in the US and Germany, trained the operators and supported the system for several years.Network Advances
Since this was a networked simulation, each simulation station needed its own display of the shared virtual environment. The display stations themselves were mock-ups of certain tankTank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...
and aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
control simulators, and they were configured to simulate actual conditions within the actual combat vehicle. The tank simulators, for example, could accommodate a full four-person crew complement to enhance the effectiveness of the training. The network was designed to support up to several hundred users at once. The fidelity of the simulation was such that it could be used to train for mission
Military operation
Military operation is the coordinated military actions of a state in response to a developing situation. These actions are designed as a military plan to resolve the situation in the state's favor. Operations may be of combat or non-combat types, and are referred to by a code name for the purpose...
scenarios and tactical rehearsals for operations performed during the U.S. actions in Desert Storm in 1992 (Robinett 1994).
The system used the concept of “dead reckoning
Dead reckoning
In navigation, dead reckoning is the process of calculating one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course...
” to collect the positions of the objects and actors within the simulated environment. Essentially this approach proposes that the current position of an object can be calculated from its previous position and velocity (which is composed of vector and speed elements) (Pimental and Blau 1994). Its use in the Gulf War demonstrates the success of the SIMNET, and its legacy was viewed as proof that realtime interactive networked cooperative virtual simulation is possible for a large user population.
Later, the Terrestrial Wideband Network (a high speed descendant of the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
that ran at T1
Digital Signal 1
Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...
speeds) was used to carry traffic. This network remained under DARPA after the rest of ARPANET was merged with NSFNet
NSFNet
The National Science Foundation Network was a program of coordinated, evolving projects sponsored by the National Science Foundation beginning in 1985 to promote advanced research and education networking in the United States...
and the ARPANET was decommissioned (Rheingold 1992).
Graphics Advances
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 PartitioningBinary space partitioning
In computer science, binary space partitioning is a method for recursively subdividing a space into convex sets by hyperplanes. This subdivision gives rise to a representation of the scene by means of a tree data structure known as a BSP tree.Originally, this approach was proposed in 3D computer...
which is computationally effective for fixed environments since polygon display order (i.e., their depth coherence) can be pre-computed. While suitable for flight simulators, which largely have a point of view above the Earth's fixed surface, this technique is ineffective near the ground, where the order in which polygons overlay each other changes with the location of the point of view. It is also ineffective with a large number of moving models, since moving a model changes its depth coherence relative to the polygons representing the ground.
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
Binary space partitioning
In computer science, binary space partitioning is a method for recursively subdividing a space into convex sets by hyperplanes. This subdivision gives rise to a representation of the scene by means of a tree data structure known as a BSP tree.Originally, this approach was proposed in 3D computer...
but was made possible in part because the cost of RAM at the time had dropped significantly in price.
SIMNET used Z-buffer displays developed by Delta Graphics. Delta Graphics was founded by Drew Johnston (SW development), Mike Cyrus (President), both from the Boeing Aerospace Company/Graphics Lab, and Jay Beck (CTO and VP), a 3D graphics consultant of Softtool Consulting. The graphics processor, the GDP, custom developed for SIMNET by Gary Wilson (Sr HW Engineer), won out over existing Silicon Graphics HW because of its low cost and because its architecture. It was the first simulator display processor to use a frame buffer and Z-buffer algorithms on a per display channel basis to show the simulated view.
Army Use of SIMNET for Training
SIMNET was actively used by the U.S. Army for training primarily at Fort BenningFort Benning
Fort Benning is a United States Army post located southeast of the city of Columbus in Muscogee and Chattahoochee counties in Georgia and Russell County, Alabama...
, Fort Rucker
Fort Rucker
Fort Rucker is a U.S. Army post located mostly in Dale County, Alabama, United States. It was named for a Civil War officer, Confederate General Edmund Rucker. The post is the primary flight training base for Army Aviation and is home to the United States Army Aviation Center of Excellence and...
, and Fort Knox
Fort Knox
Fort Knox is a United States Army post in Kentucky south of Louisville and north of Elizabethtown. The base covers parts of Bullitt, Hardin, and Meade counties. It currently holds the Army Human Resources Center of Excellence to include the Army Human Resources Command, United States Army Cadet...
. Additional temporary and permanent locations were in Fort Leavenworth
Fort Leavenworth
Fort Leavenworth is a United States Army facility located in Leavenworth County, Kansas, immediately north of the city of Leavenworth in the upper northeast portion of the state. It is the oldest active United States Army post west of Washington, D.C. and has been in operation for over 180 years...
and Grafenwoehr, Germany.
SIMNET Follow-On Programs
The follow-on protocols to SIMNET were called Distributed Interactive SimulationDistributed Interactive Simulation
Distributed Interactive Simulation is an IEEE standard for conducting real-time platform-level wargaming across multiple host computers and is used worldwide, especially by military organizations but also by other agencies such as those involved in space exploration and medicine.-History:The...
; the primary U.S. Army follow-on program was the Close Combat Tactical Trainer (CCTT).
The SIMNET-D (Developmental) program used simulation systems developed in the SIMNET program to perform experiments in weapon systems, concepts, and tactics. It became the Advanced Simulation Technology Demonstration (ADST) program. It fostered the creation of the Battle Labs across the US Army, including the Mounted Warfare TestBed
Mounted Warfare TestBed
Mounted Warfare TestBed at Fort Knox, Kentucky, was the premier site for distributed simulation experiments in the US Army for over 20 years...
at Ft Knox, Ky, the Soldier Battle Lab at Ft Benning, GA, the Air Maneuver Battle Lab at Ft Rucker, AL, the Fires Battle Lab at Ft Sill, OK.
Additional research programs after the end of SIMNET included work in weather and real-time terrain modifications.
Companies and Technologies Founded Based on SIMNET Experience
One of the primary developers of the network for SIMNET, Rolland Waters, founded RTIME, Inc. in 1992, to provide to the game industry network engines. Sony (SCEA) bought RTIME in 2000 as the basis for their PS2 online game network. Other startups out of the BBN / Delta Graphics team include:- MetaVR, Inc (W. Garth Smith), simulation and training, GIS systems
- MaK Techologies (Warren Katz and John Morrison), which continues to provide simulation software
- Zipper Interactive (Brian Soderberg), which developed the SOCOM PS2 game series and was also purchased by SCEA
- Wiz!Bang (Drew Johnston), another game developer. Drew Johnston currently is the Product Unit Manager (PUM) for the Windows Gaming Platform team at Microsoft.
External links
- Lenoir, T. and H. Lowood (2003), "Theaters of War: The Military-Entertainment Complex", Kunstkammer, Laboratorium, Bühne—Schauplätze des Wissens im 17. Jahrhundert/ Collection, Laboratory, Theater, Berlin; Walter de Gruyter Publishers.
- Vendor: Aegis Technologies: BattleStorm simulator
- SIMNET - An Insider's Perspective, L. Neal Cosby
- War is Virtual Hell, Wired Magazine Issue 1.01, Bruce Sterling
- Lockheed Martin's Close Combat Tactical Trainer (CCTT)
- Defense Advanced Research Projects Agency (DARPA) Technology Transition, pages 27, 93