(Coquillart & Janc`ene 1991) proposed an interactive technique
for animating deformable objects. They provide an alternative
to the metamorphosis method that often is used to
create intermediary shapes in order to make a smooth transition
between two key–shapes. This technique, Animated
Free–Form Deformation, relies on the Free–Form Deformation
technique described in (Sederberg & Parry 1986).