The Squash-and-Stretch Stylization for Character Animation

The squash-and-stretch describes the rigidity of the character. This effect is the most important technique in traditional cartoon animation. In this paper, we introduce a method that applies the squash-and-stretch effect to character motion. Our method exaggerates the motion by sequentially applying the spatial exaggeration technique and the temporal exaggeration technique. The spatial exaggeration technique globally deforms the pose in order to make the squashed or stretched pose by modeling it as a covariance matrix of joint positions. Then, the temporal exaggeration technique computes a time-warping function for each joint, and applies it to the position of the joint allowing the character to stretch its links appropriately. The motion stylized by our method is a sequence of squashed and stretched poses with stretching limbs. By performing a user survey, we prove that the motion created using our method is similar to that used in 2D cartoon animation and is funnier than the original motion for human observers who are familiar with 2D cartoon animation.