The goal of a practical facial animation retargeting system is to reproduce
the character of a source animation on a target face while providing room
for additional creative control by the animator. This paper presents a novel
direct method for facial animation retargeting. Our approach starts from the
basic principle that the source and target movements should be similar. By
interpreting movement as the derivative of position with time, and adding
suitable boundary conditions, we formulate the retargeting problem as a
Poisson equation. Specified (e.g. neutral) expressions at the beginning and
end of the animation as well as any user specified constraints in the middle
of the animation serve as boundary conditions. In addition, a modelspecific
prior is constructed to represent the plausible expression space of
the target face during retargeting. A Bayesian formulation is then employed
to produce target animation that is consistent with the source movements
while satisfying the prior constraints. We apply the proposed method to
retarget various facial animations to arbitrary target faces. The resulting animations
show the same temporal coherence and character of the source animations
and exhibit smooth and controlled propagation of user edits across
surrounding frames.
