Shape interpolation is a common and simple technique to control synthetic faces and stems from the early work of Parke [102]. The process operates as follows: A database of discrete facial postures is created from 3D digitizers, stereo-photogrammetry, or optical scanners [137][31]. These facial data sets have the property of topological equivalence, such that a complete mapping can be found for each vertex in every facial posture. Once a complete set is derived, then inbetween interpolation of the [x,y,z] coordinates can be computed. Unfortunately, this technique is limited to the matrix of facial postures which prompted the development of parameterization schemes.