Stable inverse dynamic curves

Alexandre Derouet-Jourdan, Florence Bertails-Descoubes, Joëlle Thollot
2010 ACM SIGGRAPH Asia 2010 papers on - SIGGRAPH ASIA '10  
Figure 1 : From left to right: The user sketches a smooth curve over the tail of a character. The curve is automatically converted into a dynamic rod model at stable equilibrium under gravity. The user can then animate the curve (e.g., pull then release it) with the guarantee that the chosen initial shape will be preserved after slight (or possibly strong) motion. See the accompanying video for the full animation. Abstract 2d animation is a traditional but fascinating domain that has recently
more » ... gained popularity both in animated movies and video games. This paper introduces a method for automatically converting a smooth sketched curve into a 2d dynamic curve at stable equilibrium under gravity. The curve can then be physically animated to produce secondary motions in 2d animations or simple video games. Our approach proceeds in two steps. We first present a new technique to fit a smooth piecewise circular arcs curve to a sketched curve. Then we show how to compute the physical parameters of a dynamic rod model (super-circle) so that its stable rest shape under gravity exactly matches the fitted circular arcs curve. We demonstrate the interactivity and controllability of our approach on various examples where a user can intuitively setup efficient and precise 2d animations by specifying the input geometry.
doi:10.1145/1882262.1866159 fatcat:galcedwuqjen7goletonloy2pe