In early applications of distributed simulation, battles occurred during mid-summer at high noon on a clear day with just enough atmospheric attenuation to prevent the visual anomaly of seeing off the edge of the "world". The Synthetic Environments (SE) Program, part of the Synthetic Theater of War (STOW-97) Advanced Technology Concept Demonstration (ATCD), is developing an architecture and the processes to represent dynamic environments with increased fidelity. Part of the SE Program is the Dynamic Virtual Worlds (DVW) effort, tasked to enrich the virtual battlefield with a range of real-world environmental effects, such as clouds, battlefield smoke, vehicular dust, natural and artificial illumination, and atmospheric transmittance.

This paper describes the work performed under DVW to advance the current state of the art in the visual representation of environmental phenomena in virtual worlds. The implementation, known as the Virtual World Environment System (VWES), provides the management and computation of environmental changes in the virtual world. Physically-based environmental are incorporated into VWES, and provide a greater level of simulation fidelity. In a Distributed Interactive Simulation (DIS) environment, VWES receives Environmental State Messages, interprets the message data, executes the appropriate physical models, coordinates interactions among models and contributes to the visual image accordingly.

The VWES architecture is designed and implemented such that it can easily be integrated into visual simulation systems and can incorporate new physical models. The architecture includes two Application Program Interfaces (APIs), one which allows the visual simulation application to provide environmental data to VWES and control its operation, and one which allows VWES to communicate its results. A model registration mechanism provides a flexible means of registering one or more environmental models on a per exercise basis.

VWES has been integrated into two visual simulation systems: the NPSNETIV. 6 Stealth and the VISTAWORKS ModStealth. Demonstration of the overall environmental simulation system is provided through interaction and correlation with its Computer Generated Forces (CGF) counterpart, ModSAF, and other environmental servers which issue environmental updates via the DIS network.