This paper describes the implementation of the sound system used to generate aural cues for use in the distributed virtual environment of NPSNET. This sound system is called the NPSNET-3D Sound Server. It is a MIDI-based loudspeaker system consisting of commercial, off-the-shelf equipment. This sound system currently generates 2-D aural cues via four speakers, but is designed for the potential generation of 3-D aural cues via a cube con®guration of eight speakers.

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.

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.