Robust and Accurate Skeletal Rigging from Mesh Sequences

Binh Huy Le and Zhigang Deng

ACM Transactions on Graphics 33(4) - Proceedings of ACM SIGGRAPH 2014

Only using a single set of parameters, our example-based method can accurately rig various models such as quadrupled animals (a), humans (b, c), and highly deformable models (d). Our method can even generate bone structures for challenging parts, such as the mouth and the two ears of the cat (a), the skirt (b), and the elastic cow model (d). Our method is robust: using only 9 frames, it can generate a skeleton with 28 bones for the cat model (a); note that even though the given example poses of the cat model have asymmetric poses, it still can generate an almost symmetric skeleton without imposing any symmetry constraints.

Abstract: We introduce an example-based rigging approach to automatically generate linear blend skinning models with skeletal structure. Based on a set of example poses, our approach can output its skeleton, joint positions, linear blend skinning weights, and corresponding bone transformations. The output can be directly used to set up skeleton-based animation in various 3D modeling and animation software as well as game engines. Specifically, we formulate the solving of a linear blend skinning model with a skeleton as an optimization with joint constraints and weight smoothness regularization, and solve it using an iterative rigging algorithm that (i) alternatively updates skinning weights, joint locations, and bone transformations, and (ii) automatically prunes redundant bones that can be generated by an over-estimated bone initialization. Due to the automatic redundant bone pruning, our approach is more robust than existing example-based rigging approaches. Furthermore, in terms of rigging accuracy, even with a single set of parameters, our approach can soundly outperform state of the art methods on various types of experimental datasets including humans, quadrupled animals, and highly deformable models.

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