Faking Dynamics of Ropes and Springs

We describe a simple method for modeling flexible linear bodies such as ropes and springs, using no dynamic simulation, procedural animation, nor constraint methods—animators create motion by adjusting the shape of models over time using traditional keyframe methods. The approach taken is to provide a default natural rest shape, and to provide controls that perform gross modification and wave-shaped deformation of the rest shape. The resulting models provide animators with intuitive control and the means to interactively create motion that is both visually plausible and tailored to the frame-to-frame needs of particular animations. This technique has been used successfully in animation production over the past few years, in particular for various ropes and the “Slinky Dog” in the movie Toy Story.