Real-time simulation of a stretcher evacuation in a large-scale virtual environment

This paper presents a case study of navigation and manipulation in a large, geometrically complex, virtual environment representing an off-shore gas platform. Our approach is based on a combined force-field navigation and collision detection algorithm. After describing the basic algorithm, we extend and apply it to a real-time simulation of two avatars carrying a third avatar on a stretcher. The extensions include a probing technique, using a virtual foot and simulated gravity, to permit ascending and descending stairs and ladders. A set of constraints between the stretcher and avatars enforces realistic lifting positions. The simulation is controlled interactively with a hand-held 3D mouse. The force fields assist the user in manoeuvring through tight spaces, while collision detection guarantees that neither the stretcher nor the avatars can pass through obstructions, such as pipe-work or hand-rails. Results are presented for a case study of a complete simulation running on a PC with a moderately fast 3D graphics card. These demonstrate that the method delivers a useful frame rate for the off-shore gas platform.