Automatic skinning and weight retargeting of articulated characters using extended position-based dynamics

Abstract

Animating an articulated character requires the explicit specification of interior skeleton structure and its attachment to skin surface. This task of “rigging” typically involves the manual weight painting and deformation fine-tuning with popular conventional animation methods. Weight painting is unavoidably a time-consuming and laborious process that would need sophisticated skills from animators during animation production. In this paper, using the extended position-based dynamics (PBD), we have articulated a strategy to generate the realistic skin deformation and reuse the painted weights on a new character. For each frame, the skin is deformed by the linear blend skinning method (LBS) at first. To solve the problem of candy-wrapper effect and surface overlapping in LBS, we improve the traditional PBD method by adding energy constraints and employ several geometrically and physically-based constraints to refine the deformed skin automatically. To further reduce the animator’s workload from tedious rigging process, we propose the weight retargeting approach using surface matching and interpolation based on the powerful bi-harmonic distance. It could transfer the weights of an existing model to a new character with similar topology. Through numerous experiments, we could demonstrate the visual performance of our new techniques on a variety of articulated characters.