Dynamically simulated characters in virtual environments

Virtual environments and games often include animated characters that must respond to the actions of the user. The unpredictable actions of the user require a highly interactive environment that is not amenable to motion generation techniques based on a library of prede ned sequences. In this paper, we present one approach to populating interactive virtual environments: using dynamic simulation to generate the motion of characters that respond in real time to the actions of the user. Simulation provides an e ective way to generate realistic and compelling motion for virtual environment applications in which realism is essential. To illustrate the use of simulation in virtual environments, we have built two environments with interactive characters ( gure1). The rst is a game in which a herd of one-legged hopping robots moves around the environment. The user navigates by steering and pedaling a stationary Tectrix bicycle and attempts to herd the robots into a corral. Each robot has knowledge of the locations of the other robots and of the user and uses that knowledge to avoid collisions in a reactive fashion. This environment served as an aggressive testbed for control algorithms for dynamically simulated robot groups[1] and as a driving application for distributed computing[2]. The second environment is a virtual recreation of the Atlanta Bicycle Road Race of the 1996 Olympics. The goal is to create a virtual environment where an athlete can experience the course both visually and physically in the presence of simulated bicyclists. Such an environment should prove valuable to the avid biker or professional racer who is limited by time, money, bad weather conditions, or insu cient situational training. For example, the racers at the Olympics are allowed only limited training time on the course without tra c and might bene t from additional time to tune their racing strategies to a particular course or eld of competitors. We plan to explore the use of this system for both physical and strategic training for individuals and teams. The virtual environment is designed to accurately re ect the terrain of the road race. Using topographic