NPSNET: Constructing A 3D Virtual World Michael J. Zyda*, David R. Pratt, James G. Monahan, Kalin P. Wilson Naval Postgraduate School Department of Computer Science Monterey, California 93943-5100 [email protected] *contact author Abstract The development of 3D visual simulation systems on inexpen- sive, commercially available graphics workstations is occurring to- day and will be commonplace in the near future. Such systems are being constructed to move through and interact with 3D virtual worlds. There are a variety of goals for these systems, including training, planning, gaming and other purposes where the introduc- tion of the physical player may be too hazardous, too expensive or too frivolous to be tolerated. We present one such system, NPS- NET, a workstation-based, 3D visual simulator for virtual world ex- ploration and experimentation. Virtual World Systems The attention to virtual world systems is particularly appealing to the researchers of the Graphics and Video Laboratory of the De- partment of Computer Science at the Naval Postgraduate School as our focus for years has been on the production of prototype 3D vi- sual simulation systems on commercially available graphics work- stations {9.18-25].3D visual simulation systems have many of the characteristics of virtual world systems in that their purpose has long been for visualizing and interacting with distant, expensive or hazardous environments. If we turn off some of our physical mod- eling, we can even simulate nonexistent 3D environments, so we feel quite comfortable under the virtual worlds umbrella. We do not study the construction of our 3D visual simulators on specially-designed graphics hardware. We instead assume that such hardware is available from commercial workstation manufacturers. We build 3D visual simulators on inexpensive graphics worksta- tions instead of specially-designed hardware because of our obser- vation that the performance numbers from the manufacturers are so suggestive. NPSNET: Overview The Graphics and Video Laboratory has been developing low- cost, three-dimensional visual simulation systems for the last six years on Silicon Graphics, Inc. IRIS workstations. The visual sim- ulators developed include the FOG-M missile simulator, the VEH vehicle simulator, the airborne remotely operated device (AROD), the Moving Platform Simulator series (MPS-1, MPS-2 and MPS- Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commerciaf advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. o 1992 ACM 0-89791.471-6/92/0003/0147...S1.50 3). the High Resolution Digital Terrain Model (HRDTM) system, the Forward Observer Simulator Trainer (FOST). the NPS Autono- mous Underwater Vehicle simulator (NPSAUV), and the Com- mand and Control Workstation of the Future system (CCWF). Our current visual simulation efforts are on tbe NPSNET SYS- tern. a workstation-based, 3D visual simulator that utilizes SIM- NET databases and networking formats. The DARPA-sponsored SIMNBT project had the goal of developing a low-cost tank simu- lator that provided a “70% solution” to the tank-war-gsming prob- lem [17]. Unfortunately, the SIMNET system delivered has its graphics hardware and software suffering from a rigid specification based on 1983 graphics technology and was not designed to take advantage of ever faster and more capable graphics hardware and processor power. Low-cost for the project meant $2SOK per station. Instead, the contractor designed its own graphics platform, its own process- ing system, and wrote software that worked only on that platform. In NPSNBT, we want to be somewhat more flexible BUT still in- teract with the DARPA investment. The NPSNET system is an attempt to explore the SIMNET do- main using a readily available graphics workstation, the Silicon Graphics, Inc. IRIS workstation in all its incarnations (Personal IRIS, GT, GTX, VGX...), instead of the contractor produced hard- ware. Our starting point is that we assume databases and network packet formats in a form similar to those utilized by the actual SIM- NET system but allow the flexibility for continuing evolutions in efficiency. NPSNET is a real-time, 3D visual simulation system capable of displaying vehicle movement over the ground or in the air. Displays show on-ground cultural features such as roads, buildings, soil types and elevations. The user can select any one of 500 active ve- hicles via mouse selection and control it with a six degree of free- dom spaceball or button/dialbox. In between updating events, all vehicles are &ad reckoned to determine their current positions. Speed in three dimensions and the location of the vehicle can accu- rately be predicted as long as the speed or direction of the vehicle does not change. Vehicles can be controlled by a prewritten script, or can be driven interactively from other workstations, as the sys- tem is networked via Ethernet. Additionally, autonomous players can be introduced into the system via a programmable network “harness” process (NPSNET-HARNESS). As obvious from the above overview, NPSNET is in many ways a departure from the goals of SIMNET. We can “push the enve- lope” of real-time, workstation-based virtual reality while provid- ing a worhtation-based SIMNET node. We present our plan for the overall NPSNET effort in the following sections to provide an un- derstanding of what is required to construct such a system. 147SIMNET Database Display Work The frost effort in any virtual world development is obtaining the data that represents the world to be modeled. For 3D visual sim- ulations, this usually begins with a large 2D grid of elevation data that is turned into a 3D terrain carpet. Once the terrain carpet has been extracted and displayed. atten- tion then turns to on-ground cultural features and 3D vehicle icons. On-ground cultural features