1. A method, implemented in a computer system, comprising: generating facial muscle activations from facial marker data by determining weights that characterize a weighted combination of action units approximating the facial marker data, wherein each action unit of the action units defines a predetermined facial muscle activation that produces a change in facial appearance; animating, the computer system, a computer graphics facial model using the facial muscle activations; generating a skin layer overlaying the computer graphics facial model; and animating the skin layer using the facial marker data.