During the past five years, Workshops on Standards for the Interoperability of Distributed Simulations have provided the forum for establishing standards for networking dissimilar simulations to create virtual worlds in which many subjects can interact. These virtual worlds can be used for training individuals, testing equipment, prototyping products, research and development or any application involving the interaction of groups of people in a common synthetic environment. The Distributed Interactive Simulation (DIS) Vision document1 produced by the workshop describes the domain of interest as follows.
"The primary mission of DIS is to define an infrastructure for linking simulations of various types at multiple locations to create realistic, complex, virtual "worlds" for the simulation of highly interactive activities. This infrastructure brings together system built for separate purposes, technologies from different eras, products from various vendors, and platforms from various services and permits them to interoperate. DIS exercises are intended to support a mixture of virtual entities (human-in-the-loop simulators), live entities (operational platforms and test and evaluation systems), and constructive entities (wargames and other automated simulations)."
Not only must DIS achieve interoperabilty among different simulations and simulation domains, it must also attain interoperability among different physical and behavioral representations of the environment, establish a means to manage these virtual worlds, and use communication networks to link them together.
As the power and potential to create robust Distributed Interactive Simulation environments gains recognition, the need for establishing standards for the implementation of these principles grows dramatically. The following paper will discuss the DIS standards development effort by describing the standards infrastructure and the process by which standards are created.
This paper analyzes the use of dead reckoning in Distributed Interactive Simulation. The purpose of dead reckoning is to reduce the updates required by each simulator on the network to better utilize the available bandwidth. Extrapolation formulas are derived and discussed based on network communication traffic and the amount of computation performed by simulators. Smoothing and delay compensation algorithms are also discussed. Numerical and human perspective experiment are conducted. A software tool that assesses the performance of the read reckoning algorithm is introduced.
Networks of simulators are a rapidly advancing technology and provide new utility for real time simulators. Simulator networking will enhance the use of simulation for training, product development, test, analysis, and creation of virtual environments. The current terminology for networks of simulators is called Distributed Interactive Simulation or DIS. DIS consists of descriptions of the protocols, the underlying network, and the architecture for connecting individual simulators. It also supports limited connectivity between real time simulators, live equipment, and discrete event simulations. However, DIS is only the current manifestation of simulator networking. One can look to processes pushing advances in simulator design, computer technology, communications technology, and innovative requirements development as key factors influencing simulator networking. These processes have been on-going for nearly thirty years. It is important to reflect on these development efforts to chart the future course for networked simulators.
Simulator Networking (SIMNET) began with a young scientist's idea but has ended up changing an entire industry and the way the military does business. And the story isn't over yet. SIMNET began as an advanced research project aimed at developing a core technology for networking hundreds of affordable simulators worldwide in real time to practice joint collective warfighting skills and to develop better acquisition practices. It was a daring project that proved the Advanced Research Projects Agency (ARPA) mission of doing “what cannot be done.” It was a serious threat to the existing simulation industry. As it turned out, the government got what it wanted—a low-cost, high-performance virtual simulation capability that could be proliferated like consumer electronics. This paper provides an insider's view of the program history, identifies some possible lessons for future developers, and opines future growth for SIMNET technology.
The Distributed Interactive Simulation (DIS) protocol for networking simulators is discussed in relation to the TCP/IP and OSI protocols. The application of various network topologies and hardware media to DIS is discussed. The semantic content of the DIS data transmissions is introduced.
In distributed interactive simulation (DIS), each node is responsible for maintaining its own model of the synthetic environment. Problems may arise if significant inconsistencies are allowed to exist between these separate world views, resulting in unrealistic simulation results or negative training, and a corresponding degradation of interoperability in a DIS simulation exercise. In the DIS community this is known as the terrain database (TDB) correlation problem. In this paper we investigate the terrain database correlation problem and the resultant effects on interoperability in DIS systems. The fundamental elements of terrain databases designed for real-time distributed simulation are introduced. A generic data pipeline for terrain database generation systems is developed for the purpose of illustrating causes of the correlation problem and issues of terrain database fidelity. Implications of the problem are discussed, and testing methodologies are recommended for its mitigation
The recent profound change in the geo-political alignment of nations, fall of Soviet Communism, economic reform at home, lessons learned from Operation DESERT STORM, and increased reliance on the military to execute Operations Other Than War (OOTW), has resulted in a Modernization renaissance throughout the Department of the Defense. Focused by a diminished strategic threat and reduced budget, the Army must tackle the challenge of realism and accurate Comand and Control capabilities across the entire spectrum of the Synthetic Environment. To accomplish this, as the DoD lead for DIS, it has formulated many new modernization strategies during the last three years to ensure its premier status as the world’s Dominant Landforce into the 21s1 Century. Responding to the National Military Strategy, the Army has established five modernization objectives that are necessary to ensure future sustainment of the warfighting force over the next decade.
The educational system within the United States has historically emphasized learning as an individual accomplishment. Working effectively with others is a skill that has been omitted from the traditional educational setting even though this reflects the modern workplace. A collaborative learning environment is one of the educational technologies being developed to address the requirement for imparting group skills within the educational system. It is a form of networked learning environment that permits students to work together on authentic learning tasks. Distributed Interactive Simulation (DIS) is a technology develop by the DoD to facilitate the integration and use of multiple simulations and simulators in a distributed collaborative computing environment. DIS can enhance collaborative learning environments in future educational applications by introducing authentic simulations of real world events into the learning experience.
Lesson modules for training laser safety are developed from a sound cognitive perspective. The lessons incorporate animated graphics designed to build a mental model in the students mind consistent with the realities of laser propagation.
This research should have applications to other types of scientific education and training and in particular to networks of training simulators such as DIS.
This paper discusses several practical considerations regarding the fidelity validation of synthetically generated and displayed infrared scenery used for smart hardware-in-the-loop (SHWIL) and man-in-the-loop simulations. Ongoing work of this type at an Orlando based aerospace company has raised technical issues which may contribute to the broader DIS "fidelity validation" program. Issues concerning the documentation of existing FLIR imagery, and their utility for fidelity comparisons to synthetic imagery are discussed. Outlined is a generic, necessarily incomplete (or open ended) scheme for IR image validation, with respect to both human and smart machine participants. Discussed are both model based, and statistically based analysis methods— with an eye on maintaining flexibility in evolving stronger fidelity validation tools over the lifetime of the project. The paper closes with recommendations on a management perspective for ongoing man-machine-in-the-loop imagery validation drawing on a dialectically motivated fact/value/practice perspective.
The experimentation and demonstration of electronic warfare (EW) capabilities in distributed interactive simulation (DIS) was performed through the development of these capabilities in the Institute for Simulation and Training’s (1ST) Computer Generated Forces (CGF) Testbed. The 1ST CGF Testbed with EW capabilities can create land, sea, and air entities that can generate and receive electromagnetic emissions across a DIS network.
Previous efforts in behavior definition for CGF systems, including the 1ST CGF Testbed, have emphasized land forces performing visual contact engagements. Adding EW capabilities to the CGF Testbed has expanded the sensing horizon of entities beyond visual range providing long range contacts for air and sea engagements. This work provided useful testing of the DIS Standards in the area of electronic warfare.
Techniques to allow simulated entities to avoid static terrain, such as trees, buildings, rivers, etc., have been in use in Distributed Interactive Simulation (DlS) environments for many years. Avoidance of objects in motion, “dynamic obstacles”, is much more complex. Although simple dynamic obstacle collision avoidance has been implemented in other systems, the resulting behavior is usually less than realistic. The Institute for Simulation and Training (1ST) has investigated techniques to allow simulated entities to make reasonably intelligent and realistic maneuvers intended to avoid dynamic (and static) objects. The goal has been to find new methods which will yield improved collision avoidance behavior without excessive computational cost. As a result of this work, 1ST has developed a novel approach to attack the DIS dynamic obstacle avoidance (DOA) problem by combining two disparate motion planning approaches: potential fields and grid based route planning.
Simulation and modeling have become an integral part of a cost-effective optical system development process. Over the years, this activity has evolved into a complex multi-disciplinary activity. To optimize the resources required for this exercise, a new concept of virtual prototyping is presented. This concept employs computer-aided interactive simulation tools such as ray tracing, solid modeling and error analysis. It addresses the broad issues of system layout, optical and optomechanical design, structural and thermal analysis for the real operating environment, tolerance budgeting and optimization procedures. This concept works in an iterative fashion to achieve the desired system performance at a minimum cost.
Distributed Interactive Simulation (DIS) is an architecture for building large-scale simulation models from a set of independent simulator nodes communicating via a common network protocol. DIS is most often used to create a simulated battlefield for military training. Computer Generated Forces (CGF) systems control large numbers of autonomous battlefield entities in a DIS simulation using computer equipment and software rather than humans in simulators. CGF entities serve as both enemy forces and supplemental friendly forces in a DIS exercise. Research into various aspects of CGF systems is ongoing. Several CGF systems have been implemented.
Existing Distributed Interactive Simulation (DIS) systems (which are a class of virtual simulations) are limited by computational power and network bandwidth in the number of vehicle platforms that can take part in a single battlefield simulation. One way to improve this limit is to integrate an aggregate constructive wargame into the DIS simulation; the constructive wargame supplies the context for a large-scale battle without adding significant computational load to the network. A critical idea in such an integration is that the events in the constructive simulation influence the events in the virtual battlefield and vice versa; this maintains the unity of the entire battlefield simulation.
This paper is a tutorial on the problem of integrating constructive and virtual simulations. It describes constructive and virtual simulations, discusses motivations for integrating such simulations, and addresses general problems that must be solved by any constructive and virtual integration.
Intervisibility between entities in a Distributed Interactive Simulation (DIS) environment is a mandatory, computationally expensive process. A Computer Generated Forces (CGF) system must determine the intervisibility status between each of its controlled entities and each of the other entities in the simulation and it must make these determinations at frequent intervals. Previous work has focused on developing algorithms to perform intervisibility determinations as quickly as possible. In this work, the problem was approached differently. Instead of speeding each intervisibility determination, heuristics were developed for reducing the number of determinations needed, thereby reducing the computational expense of intervisibility. These results are independent of terrain representation and thereby applicable to any CGF system.