A shape control method for soap bubble simulation using external forces

Simulating realistic behaviors of soap films is a challenging problem because the soap films have complex behaviors. In the computer simulation, various methods have been proposed to simulate these realistic behaviors. On the other hand, in computer graphics, many control methods have been proposed for fluid simulations, in order to create desired fluid animations for entertainment applications such as movies and video games. However, most of these studies do not focus on soap film simulations. This paper proposes a control method for soap film simulations in order to create soap bubbles with various shapes. Our control is performed by adding external forces to the simulation, and these external forces are calculated from user-specified target shapes. We adopt a surface-only soap film simulation based on the hyperbolic mean curvature flow because this formulation allows us to simply add external forces to motions of films. To enhance controllability around areas with sharp points, surface tensions are averaged for whole surface. Our system can also control magnitudes of global vibration until soap bubbles form target shapes by introducing intermediate shapes representing between an initial bubble and target shapes. We show control capability of our system by demonstrating various examples.