Example-Based Skinning Animation

Abstract

The skinning technique has been widely used for synthesizing the natural skin deformation of human-like characters in a broad range of computer graphics applications. Many skinning methods have been proposed to improve the deformation quality while achieving real-time computational performance. The design of skinned character models, however, requires heavy manual labor even for experienced digital artists with professional software and tools. This chapter presents an introduction to an example-based skinning method, which builds a skinned character model using an example sequence of handcrafted or physically simulated skin deformations. Various types of machine learning techniques and statistical analysis methods have been proposed for example-based skinning. In this chapter, we first review state-of-the-art skinning techniques, especially for a standard skinning model called linear blend skinning that uses a virtual skeleton hierarchy to drive the skin deformation. Next, we describe several automated methods for building a skeleton-based skinned character model using example skin shapes. We introduce skinning decomposition methods that convert a shape animation sequence into a skinned character and its skeleton motion. We also explain a practical application of skinning decomposition, which builds a so-called helper bone rig from an example animation sequence. We finally discuss the future directions of example-based skinning techniques.