Facial animation can be generated using keyframing, parameterization, or physics-based facial modeling. To represent facial expression, an expression library is convenient. The Facial Action Coding System (FACS) [37] is the most common method to describe facial expressions. FACS describes the set of all possible basic actions (Action Units) performable on a human face. Some sample Action Units are Inner Brow Raiser, Lid Tightener, Lip Corner Depressor. A multi-layered approach has been proposed for efficient control of facial animation [66]