The objective of facial parameterization is to present the user with a small set of control parameters for the face . These parameters are hard-wired into a particular facial geometry, and the parameters are only loosely based on the dynamics of the face. For example, the expression on the brow from surprise involves the manipulation of five or six vertices of the facial geometry.
Alternatively, distances measured between non-anatomical points (such as lip internal height or width) can be used to predict 3-D parametric contour functions . This is particularly useful in the case of the lips, which follow regular rules of deformation.