A Virtual Environment for Interactive Assembly Simulation: From Rigid Bodies to Deformable Cables

This paper presents the application of rigid body simulation for assembly tasks in a virtual environment and the extension of this system to the real-time simulation of deformable cables. Presently our virtual reality tools evaluate virtual prototypes based on CAD models of the design department. We motivate the need for deformable objects, especially cables, by practical examples and explain our physically based simulation approach. The physical behaviour of a cable is simulated as a mass-spring model with generalized springs. The main objective is a physically plausible real-time simulation for cables of moderate complexity. In comparison to research done in the field of cloth simulation for computer animation, cables show a very stiff bending behaviour. In order to improve dynamic bending behaviour we use torsion springs. Their restoring forces are proportional in angle and not in elongation. Special attention is given to the integration into the virtual environment for assembly simulation. Collision detection and response are necessary for the interaction with rigid bodies and with input devices used by the engineer.