Animating strings with twisting, tearing and flicking effects


Witawat Rungjiratananon, Complexity Science and Engineering, The University of Tokyo, Kashiwa, Japan.



String-like objects in our daily lives, for example shoelaces, threads, rubber cords, plastic fiber and spaghetti, have a wide variety of materials. Such string-like objects also exhibit interesting behaviors such as twisting, tearing (by stretching or twisting), and bouncing back when pulled and released. In this paper, we present a method that enables these behaviors and simulates such materials in traditional string simulation methods that explicitly represent a string by particles and segments. Specifically, we offer the following three contributions. First, we introduce a method for handling twisting effects with both uniform and non-uniform torsional rigidities. Second, we propose a method for estimating the tension acting on inextensible strings in order to reproduce tearing and flicking (bouncing back), whereas the tension for an extensible object can be computed via stretched length. The length of an inextensible object is maintained constant in general, and thus, we need a novel approach. Third, we introduce an optimized grid-based collision detection for accelerating the computation. We demonstrate that our method can produce visually plausible animations of string-like objects with various material properties, and it is a fast framework for interactive applications such as games. Copyright © 2012 John Wiley & Sons, Ltd.