A Mass Spring Model for String Simulation with Stress-Strain Handling

Abstract

In this paper we present an approach for real-time physically semi-realistic animation of strings which directly works on the positions. The main advantage of a position based dynamics is its controllability. Instability problems of explicit integration schemes can be avoided. Specifically, we offer the following three contributions. We introduce the non-elongating and non-stretchable mass spring dynamics model based on Position Based Dynamics to simulate 1D string. We introduce a method for propagating the twisting angle increments associated with each segment. In addition, collision constraints can be handled easily, penetrations can be resolved by regularly spreading the spheres along the segment followed by projection of particles to valid locations. Proposed strain limiting constraint can handle the strings fixed in multiple locations contrary to single fixed side as is common for hair models. The use of constraints provides an efficient treatment for stiff twisting and non-stretchable mass spring dynamics model. We demonstrate that our method can produce visually plausible animations.