This kind of interference between face elements is implemented in the top level parameters. The human face is built up in a hierarchical way. This structure makes the calculation of VC parameters easier. For example, only the mouth coordinate system needs to be altered when the mouth is moved. The top of the face hierarchy.
All elements have subparts.
Here only the subparts of the nose are discussed in detail. The nose is one of the most complex parts of the human face. There are a lot of geometrical properties and restrictions regarding the nose. These properties can be represented on the VC level most effectively. Thus the upper level functions can be made simple.