This thesis tackles the problem of automatically synthesizing motions of close-character
interactions which appear in animations of wrestling and dancing. Designing such motions is a daunting task even for experienced animators as the close contacts between
the characters can easily result in collisions or penetrations of the body segments. The
main problem lies in the conventional representation of the character states that is
based on the joint angles or the joint positions. As the relationships between the body
segments are not encoded in such a representation, the path-planning for valid motions
to switch from one posture to another requires intense random sampling and collision
detection in the state-space.
In order to tackle this problem, we consider to represent the status of the characters
using the spatial relationship of the characters. Describing the scene using the spatial
relationships can ease users and animators to analyze the scene and synthesize close
interactions of characters. We first propose a method to encode the relationship of
the body segments by using the Gauss Linking Integral (GLI), which is a value that
specifies how much the body segments are winded around each other. We present how
it can be applied for content-based retrieval of motion data of close interactions, and
also for synthesis of close character interactions. Next, we propose a representation
called Interaction Mesh, which is a volumetric mesh composed of points located at the
joint position of the characters and vertices of the environment. This raw representation is more general compared to the tangle-based representation as it can describe
interactions that do not involve any tangling nor contacts. We describe how it can be
applied for motion editing and retargeting of close character interaction while avoiding
penetration and pass-throughs of the body segments.
The application of our research is not limited to computer animation but also to
robotics, where making robots conduct complex tasks such as tangling, wrapping,
holding and knotting are essential to let them assist humans for the daily life
