Skeleton Extraction

Articulated figures are frequently used in computer graphics, especially in the areas of character animation and human figure modeling and animation. The animation of such figures is usually accomplished through the use of a control skeleton, often referred to as the IK skeleton, which is an articulated structure of segments and joints combined with information detailing how the surface geometry of the figure is anchored to that structure.

Articulated figures consist of two main components. The first is the geometric surface, often referred to as the "skin", which is by itself motionless. The second is the control skeleton. In order to create such figures, it is a common task for an animator to create the control skeleton for a given motionless surface. Many commercial modeling and animation packages include support for working with articulated figures. Packages such as Maya (Maya is a registered trademark of Silicon Graphics Inc.), Poser (MetaCreations Poser is a trademark of Curious Labs) and 3D Studio MAX (3D Studio MAX is a registered trademark of AutoDesk Inc.) include this kind of support. Usually, this support is expressed by providing an interface for constructing and attaching control skeletons to the models as well as libraries of pre-defined skeletons that can to be attached to the models. Nonetheless, the creation of a suitable control skeleton is often a tedious and time-consuming task even for the most experienced animator.

We propose a robust method for generating and attaching a simple control skeleton to a given polyhedral surface for use in real-time animations. Our method is based on our hierarchical decomposition algorithm. After finding the important components of an object using the decomposition algorithm, joints are hierarchically positioned between the components and attached to the surface.