Twisting, Tearing and Flicking Effects in String Animations

Witawat Rungjiratananon1    Yoshihiro Kanamori2    Napaporn Metaaphanon3    Yosuke Bando4    Bing-Yu Chen5    Tomoyuki Nishita1
1The University of Tokyo    2University of Tsukuba    3Square Enix    4TOSHIBA Corporation    5National Taiwan University

String-like objects in our daily lives including shoelaces, threads and rubber cords exhibit interesting behaviors such as twisting, tearing and bouncing back when pulled and released. In this paper, we present a method that enables these behaviors in traditional string simulation methods that explicitly represent a string by particles and segments. 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 in inextensible objects in order to reproduce tearing and flicking (bouncing back); whereas the tension for an extensible object can be easily computed via its 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 an efficient computation of collisions. We demonstrate that our method allows visually plausible animations of string-like objects made of various materials and is a fast framework for interactive applications such as games.