The Graphics and Video Laboratory of the Naval Postgraduate School (NPS) is in the process of constructing a three dimensional (3D) virtual world called NPSNET [Zyda91]. NPSNET is a low-cost, commercial workstationbased 3D visual simulator that utilizes SIMNET terrain databases and networking [Garv88]. NPSNET is programmed utilizing off-the-shelf SGI IRIS graphics workstation, rather than the platform specific nodes of SIMNET. Part of the work in constructing the NPSNET world is detecting and resolving collisions in real-time. Such collision detection and resolution has been accomplished and integrated into the latest version of NPSNET, NPSNET-2. The detection of vehicle-weapon, vehicle-vehicle and vehicle-stationary nonvehicle collisions is performed throughout the virtual world. Background Users of NPSNET are able to drive many different types of vehicles such as tanks, jets, ships, helicopters and armored personnel carriers. Up to 500 of the vehicles/objects can maneuver in the world at one time. The 500 vehicles can include autonomous vehicles that react when fired upon by either returning fire or fleeing the area. These 3D icons move around in the computer world that is based on the terrain at Fort Hunter-Liggett, California. The terrain appearance is enhanced by the inclusion of textures on many terrain details. Depending upon the model of IRIS being used, the user can select to use texturing, fog and even haze. The system is networked, via Ethernet, to allow several players to interact. A two dimensional (2D) map option shows the position and tracking of all the players in the 50 kilometer square. This map displays the direction and viewing triangle of the driven vehicle as well as the position and movement of the remaining vehicles. The statistics and data concerning the driven vehicle are displayed in a window at the top of the screen. Speed, pitch, roll, number of remaining rounds and remaining fuel are a few of the statistics shown. Players control their chosen vehicles through several interface devices including a button/dialbox, keyboard and SpaceBall. The Spaceball is a single device used to control an object’s six degrees of freedom. The pick button on the SpaceBall fires the appropriate weapon associated with the vehicle being driven. Applying pressure to the SpaceBall adds to the thrust in the applied direction; twisting the Spaceball changes the object’s orientation. This allows the player to turn, move forward, backward, up and down very quickly. Since the system runs in real-time, reactions to events, not just the detection of them, have to take place very quickly. This includes following terrain contours, reacting to input from the user and responding to changes in the 3D world. As long as no collision occurs, the displays on the original NPSNET, NPSNET-1, are realistic.
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