Skeleton extraction from a mesh for easy skinning animation.

This paper proposes the extraction of a skeleton and skinning weights from a given mesh, describes how to store computed data in Collada 1.5 and use it for an animation. Firstly, the mesh is contracted using constrained Laplacian smoothing in a few iterations. Few vertices from the contracted mesh are chosen as control points. Multiple edges are removed and vertices that are very close to each other are merged using a greedy algorithm minimizing the energy. The greedy selection is applied repeatable until we have the tree structure with edges corresponding to bones. We also propose the automatic assignment of the skinning weights that determine the rigid or soft mesh deformations. In the postprocessing stage the user can inspect the skeleton by previewing skinning deformations, make desired changes and export the skeleton to Collada 1.5. Transformation matrices used in a hierarchical skeleton tree are not transformed to joint's local transformation frame, so they are immediately compatible with majority of animation software and libraries.