Achieving high-quality shape deformation in real time

Though popular, linear blending schemes remain difficult to use because they require manual bone-weight painting or modeling of enclosing cages. We automatically compute linear blending weights that produce smooth and intuitive deformations for points, bones and cages of arbitrary topology. Our weights, called bounded biharmonic weights, minimize the Laplacian energy subject to bound constraints. Doing so spreads the influences of the controls in a shape-aware and localized manner, even for objects with complex and concave boundaries. We demonstrate successful use of our blending weights for real-time deformation of 2D and 3D shapes.

After defining bending weights, traditional animation interfaces require all skinning transformations to be specified explicitly, typically using a control structure (a rig). Our system allows the user to specify only a subset of the degrees of freedom and the rest are automatically inferred using nonlinear, rigidity energy minimization. Our algorithm runs orders of magnitude faster than previous nonlinear deformation methods without compromising quality. In addition, our approach also opens the door to new modes of control: disconnected skeletons combined with shape-aware inverse kinematics. By automatically generating extra skinning weights, our method can also be used for fast variational shape modeling.