linear blend skinning (lbs) · cap 5726 - computer graphics - fall 18 – xifeng gao florida state...
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CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning (LBS)
Acknowledgement: Daniele Panozzo, Alec Jacobson
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
LBS generalizes to different handle types
skeletons regions points cages
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning rigging preferred for its real-time performance
place handles in shape
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning rigging preferred for its real-time performance
place handles in shape paint weights
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning rigging preferred for its real-time performance
place handles in shape paint weights deform handles
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning rigging preferred for its real-time performance
place handles in shape paint weights deform handles
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Linear Blend Skinning rigging preferred for its real-time performance
place handles in shape paint weights deform handles
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Challenges with LBS
• Weight functions wj• Can be manually painted or
automatically generated• Degrees of freedom Tj
• Exposed to the user (possibly with a kinematic chain)
• Richness of achievable deformations
• Want to avoid common pitfalls – candy wrapper, collapses
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Properties of the Weights
Handle vertices
Interpolation of handlesPartition of unity
is linear along cage faces
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Weights Should Be Positive
Unconstrained biharmonic[Botsch and Kobbelt 2004]
Bounded Biharmonic Weights[Jacobson et al. 2011]
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Weights Should Be Smooth
Bounded Biharmonic Weights
Extension of Harmonic Coordinates[Joshi et al. 2005]
[Jacobson et al. 2011]
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Weights Should Be Smooth
Bounded Biharmonic Weights Extension of Harmonic Coordinates[Joshi et al. 2005]
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Different Types of Handles
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
is linear along cage faces
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
is linear along cage faces
Constant inequality constraints
Partition of unity
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
is linear along cage faces
Constant inequality constraints
Solve independently and normalize
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Bounded biharmonic weights enforce properties as constraints to minimization
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Some examples of LBS in action
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Some examples of LBS in action
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Some examples of LBS in action
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
3D Characters
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Mixing different handle types
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Skinning Decomposition for Rigid Bones
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
Skinning Decomposition for Skeletons
CAP 5726 - Computer Graphics - Fall 18 – Xifeng Gao Florida State University
ReferencesFundamentals of Computer Graphics, Fourth Edition 4th Edition by Steve Marschner, Peter ShirleyChapter 16
Skinning: Real-time Shape DeformationACM SIGGRAPH 2014 Coursehttp://skinning.org