This paper presents a new method for editing and retargeting motions
that involve close interactions between body parts of single
or multiple articulated characters, such as dancing, wrestling, and
sword fighting, or between characters and a restricted environment,
such as getting into a car. In such motions, the implicit spatial relationships
between body parts/objects are important for capturing
the scene semantics. We introduce a simple structure called an
interaction mesh to represent such spatial relationships. By minimizing
the local deformation of the interaction meshes of animation
frames, such relationships are preserved during motion editing
while reducing the number of inappropriate interpenetrations. The
interaction mesh representation is general and applicable to various
kinds of close interactions. It also works well for interactions involving
contacts and tangles as well as those without any contacts.
The method is computationally efficient, allowing real-time character
control. We demonstrate its effectiveness and versatility in
synthesizing a wide variety of motions with close interactions.