Elasticity-Inspired Deformers for Character Articulation

Ladislav Kavan Olga SorkineEidgenössische Technische

Hochschule Zurich

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Character Articulation

- Requires skeletal manipulation and skin mesh deformations

- Realistic mesh deformation achieved by minimizing elastic energy over voxel space

- Too slow for real-time…

- Real-Time Alternatives:

- Linear blend skinning

- Dual quaternion skinning

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Linear Blend Skinning

- Associate each mesh vertex with multiple neighboring joints using weights

- Assign weights to determine the amount of effect each joint has

- Transform vertex coordinates in relation to weights and joint transformations linearly

- Problems:

- Candy Wrapper effect

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Dual Quaternion Skinning

- Associate each mesh vertex with multiple neighboring joints using weights

- Assign weights to determine the amount of effect each joint has

- Represent desired transformations using dual quaternions

- Problems:

- Bulge effect

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Weighting Schemes

- Manual assignment of weights (really!?)

- Bounded bi-harmonic weights

- Elastic energy-minimizing weights (the authors’ approach)

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Joint-based Deformers

- Alternative to LBS and DQS

- Associate a function with each joint that describes deformations in the joint vicinity

- Weights still apply

- Swing/Twist Deformer combines advantages of LBS and DQS

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Combined Approach

- Use Swing/Twist deformers with energy minimizing weights

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Results

• http://igl.ethz.ch/projects/eid/

http://www.youtube.com/watch?v=a1K88Cs58-o&feature=youtu.be

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Limitations and Future Work

- Determining voxel size

- Designing other deformers

- Self-intersections/collisions

- Integration over continuous range of motion