A practical system for 3D facial animation should

have three features:

■■ Expression generation. It can accurately generate

realistic expressions for an arbitrary neutral face

given by coefficients.

■■ Expression retargeting or cloning. It can reproduce

an example 3D face’s expressions on any other

neutral face.

■■ Robustness. It can generate realistic facial expressions

robustly from noisy or even incomplete

3D faces.