A large number of people in streets, parks, or public squares form a crowd to show complicated scenes often appeared in applications such as computer games and movie films. Crowd simulation is a technique to automatically generate a crowd scene by simulating the behavior of the crowd.
In this paper, we address two problems in crowd simulation. First is the time complexity problem. It cost a plenty of time to simulate a crowd because a crowd is usually large in number. To address this problem we adopt the event driven collision detection algorithm. The second problem is the difficulty of designing powerful behavior generation framework. It must be powerful enough to generate many crowd behaviors especially complex ones. To address this problem, we propose a hierarchical behavior genera-tor. Hierarchical structure decompose a complex behavior into many simple behaviors. Therefore we can assemble simple low level behaviors to make a complex high level behavior easily. Furthermore, for variety of the crowd behavior, behavior generation framework enable the animator to define the motions and the decisions specifically. To do this, we use an external module for motion generation and decision making. Proposed event driven crowd simulator is fast enough to simulate many virtual characters. Also the hierarchical behavior generation framework can cover the various and complex crowd behaviors.
