DESCRIPTION
Blendshapes (linear shape interpolation models) are perhaps the most commonly
employed technique in facial animation practice. A major problem in creating
blendshape animation is that of blendshape interference: the adjustment of a
single blendshape ``slider'' may degrade the effects obtained with previous
slider movements, since the blendshapes have overlapping, nonorthogonal
effects. Because models used in commercial practice may have 100 or more
individual blendshapes, the interference problem is the subject of
considerable manual effort. Modelers iteratively resculpt models to reduce
interference where possible, and animators must compensate for those
interference effects that remain. In this short paper we consider the
blendshape interference problem from a linear algebra point of view. We find
that while full orthogonality is not desirable, the goal of preserving
previous adjustments to the model can be effectively approached by allowing
the user to temporarily designate a set of points as representative of the
previous (desired) adjustments. We then simply solve for blendshape slider
values that mimic desired new movement while moving these ``tagged'' points as
little as possible. The resulting algorithm is easy to implement and
demonstrably reduces cases of blendshape interference found in existing
models.
ACM SIGGRAPH Symposium on Interactive 3D Graphcis and Games (I3D 2005):
paper
Additional material
