Modeling and Simulation Linking Entertainment and Defense (1997) / Chapter Skim
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2 SETTING A COMMON RESEARCH AGENDA
2 SETTING A COMMON RESEARCH AGENDA
Pages 32-83
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From page 32... ...
TECHNOLOGIES FOR IMMERSIVE SIMULATED ENVIRONMENTS1 Immersive simulated environments are central to the goals and needs of both the DOD and the entertainment industry. Such environments use a variety of virtual reality (VR)
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This is why VR is so appealing to user interface researchers: it provides experience without forcing users to travel through time or space, face physical risks, or violate the laws of physics or rules of engagement. Unfortunately, creating effective experiences with virtual environments is difficult and often expensive.
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In the nonimmersive domain, experiential computing technology is being leveraged by both the Naval Research Lab (NRL) and the Army Research Lab (ARL)
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Much of this work would be applicable to both defense and entertainment applications of experiential computing technology. Technologies for image generation, tracking, perambulation, and virtual presence are of interest to both communities, but research priorities tend to be very different.
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and the GE Compuscene 4 Computer Image generators were benchmarks by which all interactive computer graphics systems were measured for years. At about the same time, interactive 3D graphics began to migrate into commercial applications.
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As real-time 3D becomes a commodity, the true cost of image generation is switching to software the time and resources required to model virtual worlds. As commercial systems become more capable, more opportunities will exist for DOD and the entertainment industry to work together on image generation capabilities, coupling fidelity with the lower costs that stem from producing larger volumes.
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From page 38... ...
Magnetic tracking is currently used for detecting head position and orientation in Disney's Aladdin experience and other attractions, despite the fact that the latency of such systems is roughly 100 milliseconds long enough to contribute to symptoms of simulator sickness.3 As the performance of graphics engines rendering virtual environments increases, the proportional effect of tracker lag is increased. Some optical-based trackers are currently yielding good results but have some problems with excessive weight and directional and environmental sensitivity.
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The U.S. Army's STRICOM has funded the development of an omni-directional treadmill to explore issues associated with implementing perambulation in virtual environments, a topic that is applicable to entertainment applications of VR as well.
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Providing more realistic sound in a synthetic environment can improve the fidelity of the sensory cues perceived by participants in a simulation and help them forget they are in a virtual simulated environment. · Olfactory stimulus.
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Designing systems that provide high levels of fidelity can be prohibitively costly, and, as discussed above, the additional levels of fidelity may not greatly improve the simulated experience. As a result, simulation designers often employ a technique called selective fidelity in which they concentrate resources on improving the fidelity of those parts of a simulation that will have the greatest effect on a participant's experience and accept lower levels of fidelity in other parts of the simulation.
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From page 42... ...
After realizing that game players spent little time looking at the controls in a flight simulator, for example, Spectrum HoloByte shifted resources to improving the fidelity of the view out the window.8 Experiments have shown that even in higher-fidelity systems the experience can be improved by telling a preimmersion background story and by giving participants concrete goals to perform in virtual environments.9 Selective fidelity is important in both defense and entertainment simulations, though it can be applied somewhat differently in each domain to reflect the importance given to different elements of the simulation. For DOD, selective fidelity is typically used to ensure realistic interactions between and performance of simulated entities, sometimes at the expense of visual fidelity.
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In addition, because of the long lifetimes of some trainers at DOD, several modern video games far exceed the accuracy of some older operational simulators. But game designers must often break with reality in order to meet budgetary and technological constraints.
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Though they are still at a simple stage, connecting only tens of players, such games are moving toward larger-scale connectivity. If the number of participants in networked games grows as large as DOD simulations (the targeted size of military simulations has increased by nearly two orders of magnitude over the past decade)
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To overcome bandwidth limitations, both the defense modeling and simulation community and providers of Internet-based games have attempted to develop or acquire greater bandwidth for their systems. DOD has constructed its own network, the Defense Simulation Internet (DSI)
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Networked game companies, cognizant that most players access the Internet via 14.4- or 28.8-kilobits-per-second modem connections, are striving to customize their network data to reduce data transmission requirements while maintaining the entertainment value of their applications. Military simulation designers have paid relatively little attention to determining which data transmissions can be dispensed with while retaining acceptable reality at the application level.
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From page 47... ...
Its Large Scale Multicast Applications working group has developed documentation to describe how IETF multicast protocols, conference management protocols, transport protocols, and multicast routing protocols can support large-scale distributed simulations, such as DOD simulations containing 10,000 simultaneous groups and upward of 100,000 virtual entities.~5 Nevertheless, additional research is needed to expand the capabilities of AOIMs beyond those of simple filters and to make them generalizable across problem domains. The IETF, for example, has identified seven areas in which existing Internet protocols are insufficient to support large-scale distributed simulation networks (see Table 2.1~.
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A set of transmission protocols that can provide the range of quality-of-service and latency requirements of distributed interactive simulations, such as best-effort multicast of most data, reliable multicast of critical reference data, and low-latency reliable unicast of data among arbitrary members of a multicast group. A protocol for managing network resources, such as the Simple Network Management Protocol used on the Internet.
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each individual machine controls all objects locally and broadcasts changes to the other machines via a central server. If a player pushes a button to make his or her character jump, for example, the player's own machine will update the position of the character and send a message to the server indicating that the jump button was pressed.
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SOURCE: Position paper prepared for this project by Will Harvey; see Appendix D In a client/server architecture each machine independently sends its user input or action request to a central server, which then relays the information to each player's client machine.
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Alternatively, some researchers are developing techniques for synchronizing events across distributed simulations.20 Such approaches assume that information from remote simulators will always be received with a time delay and that many actions cannot be predicted accurately. Thus, they show objects from remote machines with an inherent time delay.
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While having demonstrated some efficacy in game applications, additional analysis will be needed to determine the suitability of such techniques for defense simulations that require high levels of fidelity. STANDARDS FOR INTEROPERABILITY A related area of interest to DOD and the Internet games community is standards for interoperability.
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Meeting these requirements allows tank simulators, for example, to be designed and interconnected so that their operators can share information and train jointly in a common virtual battlefield. Related to this capability is composability, the ability to build simulations using components designed for other simulations.
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DIS is a group of standards developed by members of the defense modeling and simulation community (both industry and university researchers) to facilitate distributed interactive simulations.
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Development of the HLA was initiated in 1994, when DARPA awarded three contracts for the definition of a high-level architecture for advanced distributed simulations. Contractors analyzed the needs of prototype federations in four areas: (1)
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56 MODELING AND SIMULATION the HLA.25 Testing of prototype federations was completed in July 1996 to determine if the RTI was broadly enough defined to be useful across a wide range of federations. Test results informed development of the HLA Baseline Definition, which was completed in August 1996 and approved by the Under Secretary of Defense for Acquisition and Technology as the standard technical architecture for all DOD simulations in September 1996.
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Adoption of HLA beyond DOD is questionable, however; members of the entertainment industry noted at the workshop that HLA's development took place largely without their input or that of other nondefense communities. As a result, many representatives of the games community believe that HLA will not meet their needs; at the workshop
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(Box 2.2~. Interoperability in the Entertainment Industry The entertainment industry, to date, has expressed different interests regarding interoperability standards.
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Nintendo and Sega game machines cannot interoperate with each other or with computer-based video games. A flight simulator game produced by Spectrum HoloByte Inc.
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The integration effort discussions are occurring under various titles the virtual reality transfer protocol and the IETF's large-scale multicast applications working group.32 Among the component technologies that have enabled rapid exponential growth of the Web are HTML and http. HTML is a standardized page markup language that allows the placement of text, video, audio, and graphics in a nonplatform-dependent fashion.
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Research into application-level protocols and architectures must take these considerations into account. From the networked games perspective, heterogeneity in software architecture is not yet possible, although some research is being done.
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Several telephone companies and small venture-capital-funded start-ups are working on this, but no new products have been announced yet. GameScript work is similar to HLA and to the virtual reality transfer protocol work.
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According to Warren Katz, many video game companies have examined DIS protocols for suitability in their games, but few have implemented them. Some companies have found DIS protocols to be too big and complex, performing operations that were not relevant to video games and slowing the performance of the system.35 Others view DIS as a standard for military applications and do not consider it appropriate for nonmilitary games.
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The code base will need to be designed to allow easy upgrades so that designers can replace particular objects without completely redesigning the system.36 Others at the workshop suggested that HLA might be advantageous in allowing real-time simulations to interoperate with simulations that progress faster or slower than real time. In the video games world this capability would mean that a high-level strategy game that typically runs faster than real time could interoperate with a real-time simulator: a turn-based chess game could interoperate with a simulation of the motion of the pieces.
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Gilman Louie of Spectrum HoloByte estimates that three of the four years required to produce a new video game are dedicated to developing algorithms for controlling computer-generated forces. Increasingly capable computer-generated opponents have been incorporated into video games since the first commercial video game was introduced in 1970.
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PC-based games further pushed the development of high-quality computer-generated opponents. Unlike most dedicated video games (with game boxes, such as those manufactured by Nintendo, Sega, and Sony)
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Location-based Entertainment Computer-generated character technologies also appear in immersive virtual reality attractions. Walt Disney Company's Aladdin attraction, for example, puts the participant into a virtual environment with many simulated individuals performing throughout the virtual world.38 Characters such as shopkeepers, camel herders, the sultan's guards, and others populate the simulated city of Agrabah.
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semiautomated forces (SAFs) that require some direct human involvement to make tactical decisions and to control the activities of the aggregated force and (2)
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There is now a diverse and active interest throughout the DOD modeling and simulation community in the development of computer-generated forces. DARPA is sponsoring the development of modular semiautomated forces for the Synthetic Theater of War program, which includes both intelligent forces and command forces.
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Adaptability A significant problem facing the development of automated forces is that humans learn and adapt faster than most existing computer algorithms. To date, games have been short enough that computergenerated forces based on specified scripts or simple "if-then" rules could provide enough of a challenge for most players, but with persistent universes simple rule-based systems will not be good enough to control automated forces.
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As part of a DARPA program, McDonnell Douglas has developed a system that uses genetic algorithms45 to develop new behaviors and tactics for military simulations. In previous trials, tactics developed by the system were used in simulators and shown to be effective for military operations.
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The user must care about the automated forces and arrive at the same conclusions whether or not the forces under control are human or computer generated. There are many situations in which a player would move a unit into a suicidal situation with a computer-generated character but would choose not to if the force was human.
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Such tools are used to create and manipulate databases containing information about virtual environments and the objects in them, allowing different types of objects to be placed in a virtual environment and layers of surface textures, lighting, and shading to be added. For games this may be a 3D world that is realistic (such as a flight simulator)
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Real-time 3D games demand that real-world imagery, such as photographic texture maps, be combined quickly and easily with 3D models to create the virtual worlds in which pilots fly. In the highly competitive market that computer game companies face, time to market and product quality are major factors (along with quality of game play)
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DOD Applications and Interests DOD faces an even greater challenge in its modeling and simulation efforts. Because of the large number of participants in defense simulations, the department requires larger virtual environments than the entertainment industry and ones in which users can wander at their own volition (as opposed to traditional filmmaking in which designers need to create only those pieces of geometry and texture that will be seen in the final film)
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Research Challenges Database Generation and Manipulation Both the entertainment industry and DOD have a strong interest in developing better tools for the construction, manipulation, and compositing of large databases of information describing the geography, features, and textures of virtual environments. Simulations of aircraft and other vehicles, for example, require hundreds or thousands of terrain databases; filmmakers often need to combine computer-generated images with live-action film to create special effects.
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They must also allow designers to develop simulated environments in pieces that can be seamlessly linked together into a single universe. This need will become more acute as the scale of distributed simulations grows.
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DOD might be able to use some of the advanced compositing techniques that have been developed by the entertainment industry to integrate live-action video with computer graphics models. The entertainment industry's software techniques for matching motion and seamlessly integrating simulated scenes into a virtual environment might also be beneficial to DOD.
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The project created an alternative virtual reality computer system, the Virtual Director, to enhance human operator control and to capture, edit, and record camera motion in real time through high-bandwidth simulation data for film and video recording. This interactive software was used to create the camera choreography of large astrophysical simulation data sets for special effects in the IMAX movie, Cosmic Voyage.
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1996. "Disney's Aladdin: First Steps Toward Storytelling in Virtual Reality," ACM SIGGRAPH '96 Conference Procedings: Computer Graphics.
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1995. "A Network Software Architecture for Large-Scale Virtual Environments." Ph.D.
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1996. "Disney's Aladdin: First Steps Towards Storytelling in Virtual Reality," ACM SIGGRAPH '96 Conference Proceedings: Computer Graphics.
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48. See National Research Council, Virtual Reality, note 30 above.
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