Efficient planning of NPC cluster movement in computer game environment

For natural group movement of non player characters (NPCs) in a computer game, an efficient planning algorithm is necessary. This paper presents a grid window-based path planning algorithm for realistic group movement. The global path is planned in a static environment and the path is locally repaired to avoid dynamic obstacles during execution. The planning and execution processes are performed for the group, not for individual NPCs by using a 2D virtual grid window covering all the NPCs. The movement of each NPC is generated inside the grid window without complicated procedures to detect collisions. We implement and test the algorithm on a polygonal world modeling a real game background. The simulation results show that the proposed method provides natural group movement and dynamic obstacle avoidance, and the experimental result with various numbers of NPCs shows consistent performance.