David R. Pratt

Npsnet: A network software architecture for largescale virtual environments

This paper explores the issues involved in designing and developing network software architectures for large-scale virtual environments. We present our ideas in the context of NPSNET-IV, the first 3-D virtual environment that incorporates both the IEEE 1278 distributed interactive simulation (DIS) application protocol and the IP multicast network protocol for multiplayer simulation over the Internet.

NPSNET : hierarchical data structures for real-time three-dimensional visual simulation.

Abstract 3D visual simulation systems must present a world, including terrain, cultural features, and 3D icons, in real-time at a level of detail that supports the use for which the system is intended. A “simple” world lends itself to blasting all the polygons through the workstations existing graphics pipeline. However, a “simple” world is not very realistic and/or does not operate in real-time. For complex worlds, such as that modeled in NPSNET, providing high fidelity in real-time requires the use of hierarchical data structures. We explore the implementation of such a structure on the world modeled by NPSNET utilizing quadtrees.

NPSNET: a multi-player 3D virtual environment over the Internet

in the Proceedings of the 1995 Symposium on Interactive 3D Graphics, 9 - 12 April 1995, Monterey, California.

NPSNET: flight simulation dynamic modeling using quaternions

The Naval Postgraduate School (NPS) has actively explored the design and implementation of networked, real time, three-dimensional battlefield simulations on low-cost, commercially available graphics workstations. The most recent system, NPSNET, has improved in functionality to such an extent that it is considered a low-cost version of the Defense Advanced Research Project Agencys (DARPA) SIMNET system. To reach that level, it was necessary to economize in certain areas of the code so that real time performance occurred at an acceptable level. One of those areas was in aircraft dynamics. However, with off-the-shelf computers becoming faster and cheaper, real-time and realistic dynamics are no longer an expensive option. Realistic behavior can now be enhanced through the incorporation of an aerodynamic model. To accomplish this task, a prototype flight simulator was built that is capable of simulating numerous types of aircraft simultaneously within a virtual world. Besides being easily incorporated into NPSNET, such a simulator also provides the base functionality for the creation of a general purpose aerodynamic simulator that is particularly useful to aerodynamics students for graphically analyzing differing aircrafts stability and control characteristics. This system is designed for use on a Silicon Graphics workstation and uses the GL libraries. A key feature of the simulator is the use of quaternions for aircraft orientation representation to avoid singularities and high data rates associated with the more common Euler angle representation of orientation.

NPSNET: constructing a 3D virtual world

in Computer Graphics, Special Issue on the 1992 Symposium on Interactive 3D Graphics, MIT Media Laboratory, 29 March - 1 April 1992, pp. 147-156.

The software required for the computer generation of virtual environments

The first phase of virtual world development has focused on the novel hardware (3-D input and 3-D output) and the graphics demo. The second phase of virtual worlds development will be to focus in on the more significant part of the problem, the software bed underlying real applications. The focus of this paper is on the software required to support large scale, networked, multiparty virtual environments. We discuss navigation (virtual camera view point control and its coupling to real-time, hidden surface elimination), interaction (software for constructing a dialogue from the inputs read from our devices and for applying that dialogue to display changes), communication (software for passing changes in the world model to other players on the network, and software for allowing the entry of previously undescribed players into the system), autonomy (software for playing autonomous agents in our virtual world against interactive players), scripting (software for recording, playing back, and multitracking previous play against live or autonomous players, with autonomy provided for departures from the recorded script), and hypermedia integration (software for integrating hypermedia data—audio, compressed video, with embedded links—into our geometrically described virtual world). All of this software serves as the base for the fully detailed, fully interactive, seamless environment of the third phase of virtual world development. We discuss the development of such software by describing how a real system, the NPSNET virtual world, is being constructed.

Insertion of an articulated human into a networked virtual environment

Most distributed interactive simulation (DIS) technology demonstrated in recent years has focused on vehicle interaction. The dismounted infantryman-the individual soldier-has been largely ignored or represented by static models. In six weeks of development, the Naval Postgraduate School, SARCOS Inc., and University of Pennsylvania, under Army Research Laboratory sponsorship, demonstrated the insertion of a fully articulated human figure into a DIS environment. This paper describes the system architecture.<<ETX>>

NPSNET: Real-Time Collision Detection and Response

The Journal of Visualization and Computer Animation, special issue on Simulation and Motion Control, Vol. 4, No. 1, January - March 1993, pp.13-24.

Npsnet and the naval postgraduate school graphics and video laboratory

The Naval Postgraduate School Networked Vehicle Simulator IV (NPSNET-IV) is a low-cost, student-written, real-time networked vehicle simulator that runs on commercial, off-the-shelf workstations (the Silicon Graphics IRIS family of computers). NPSNET-IV has been developed at the Naval Postgraduate Schools (NPS) Department of Computer Science in the Graphics and Video Laboratory. It utilizes Simulation Network (SIMNET) databases and SIMNET and Distributed Interactive Simulation (DIS) networking formats. The DIS networking format is flexible enough to allow multiple players to game over the Internet. The availability of NPSNET-IV lowers the entry costs of researchers wanting to work with SIMNET, DIS, and follow-on systems. Without the contributions of the departments M.S. and Ph.D. candidates, the NPSNET project would be impossible to maintain and continue. The diversity of their interests accounts for the broad range of research areas within the project.

Humans in large-scale, networked virtual environments

This paper examines the representation of humans in large-scale, networked virtual environments. Previous work done in this field is summarized, and existing problems with rendering, articulating, and networking numerous human figures in real time are explained. We have developed a system that integrates together some well-known solutions along with new ideas. Models with multiple level of details, body-tracking technology and animation libraries to specify joint angles, efficient group representations to describe multiple humans, and hierarchical network protocols have been successfully employed to increase the number of humans represented, system performance, and user interactivity. The resulting system immerses participants effectively and has numerous useful applications.