SIGGRAPH Asia 2011 Preview Seminar Session 11: Animation 2011/11/25 Jun Saito Marza Animation...
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Transcript of SIGGRAPH Asia 2011 Preview Seminar Session 11: Animation 2011/11/25 Jun Saito Marza Animation...
SIGGRAPH Asia 2011
Preview Seminar
Session 11: Animation2011/11/25
Jun SaitoMarza Animation Planet, Inc.
Session 11: AnimationFacial Animation
Artist Friendly Facial Animation Retargeting
Compression and Direct Manipulation of Complex Blendshape Models
Simulated Character
Controlling Physics-Based Characters Using Soft Contacts
Modal-Space Control for Articulated Characters
Skinning Stretchable and Twistable Bones for Skeletal Shape Deformation
Artist Friendly Facial Animation Retargeting
Yeongho Seol∗, Jaewoo Seo†, Paul Hyunjin Kim‡, J.P. Lewis§, Junyong Noh¶
∗†‡¶KAIST, §Weta Digital
Artist Friendly Facial Animation Retargeting
MotivationRetargeting from facial motion capture does not yield enough efficiency
Method Manual Key-framing Retargeting Edits
Total time 40 min. 36 min.
Time required to edit 135 frames of animation
Side Note:Facial Retargeting EfficiencyTechnology X used at Marza
Method Manual Key-framing Retargeting Edits
Total time 24 hrs. 5 hrs.
Artist Friendly Facial Animation Retargeting
System Overview
Automatic GUI
Generation
Sequential Retargeting
Graph Simplificati
on
Artist Friendly Facial Animation Retargeting
Automatic GUI Generation
• Facial rig w/ arrow-like GUIo Compute dominating motion vector of each blendshape target by
WPCA
• Grouping of GUI to regions and layerso Manually paint four regions: mouth, forehead, eyes, and otherso Three layers (large, mid, small) depending on the total
displacement from neutral face
Artist Friendly Facial Animation Retargeting
RetargetingCompute marker correspondence (generic face to actor’s face)by RBF warping
Artist Friendly Facial Animation Retargeting
RetargetingConventional (non-sequential) retargeting
Capturedmarker positions
Marker positionsof blendshapes
Artist Friendly Facial Animation Retargeting
Sequential retargeting
• Solve NNLS for blendshape target starting with largest total displacement
• Mimics animators’ workflow (coarse posing, then fine tuning)
Retargeting
Artist Friendly Facial Animation Retargeting
1. Find optimal salient points using dynamic programming
2. Find piecewise optimal Bezier curve
Graph Simplification
Artist Friendly Facial Animation Retargeting
Results GUI Seq. Graph Test 1 Test 2 Avg. Time
Face 1 (a) Manual key-framing 36 42 39
(b) Y N N 32 36 34
(c) Y N Y 30 36 33
(d) Y Y N 18 20 19
(e) Y Y Y 15 19 17
Face 2 (a) Manual key-framing 26 23 24
(b) Y N N 18 18 18
(c) Y N Y 17 15 16
(d) Y Y N 9 7 8
(e) Y Y Y 8 5 6
Minutes required to edit 135 frames of animation
Compression and Direct Manipulation of Complex
Blendshape ModelsJaewoo Seo∗, Geoffrey Irving†, J.P. Lewis‡, Junyong Noh§
∗§KAIST, †‡Weta Digital
Compression and Direct Manipulation of Complex Blendshape Models
Facial Blendshapes @ Weta:o 42,000 verticeso 730 targetso Density close to 100%o 8 fps on 8 core CPU
Generic model for feature-quality, semi-realistic character• 6,821 vertices• 96 targets• Average density: 10% (max 30%)
Perhaps sparse matrix implementation is enough?
Side Note:Blendshapes @ Marza
Compression and Direct Manipulation of Complex Blendshape Models
Make humongous blendshapes more tractablewith lossy matrix compression using
hierarchical semi-separable (HSS) representation
Technique can be applied to compression and speed-up of large matrix multiplication
Contributions
Compression and Direct Manipulation of Complex Blendshape Models
CompressionPreparation: reordering
o Place high-rank blocks on “diagonal,” low-rank blocks on “off-diagonal”o Exact permutation is NP hardo Find bisection by minimizing crossing weight below, use heuristic in
[Kernighan and Lin 1970]
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHierarchical Semi-Separable (HSS) Representation
Tree of orthogonal matrices to compresssignificant off-diagonal structure
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHSS Construction [Xia et al. 2010]
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHSS Construction [Xia et al. 2010]
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHSS Construction [Xia et al. 2010]
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHSS Construction [Xia et al. 2010]
Compression and Direct Manipulation of Complex Blendshape Models
CompressionHSS Construction [Xia et al. 2010]
Compression and Direct Manipulation of Complex Blendshape Models
Compression• Perform SVD on matrix blocks, drop singular
values
• Optional: represent rotation using banded Householder factorization [Irving 2011]
Compression and Direct Manipulation of Complex Blendshape Models
Parallel ProcessingGPU-optimized HSS-compressed matrix multiplication
Compression and Direct Manipulation of Complex Blendshape Models
More Applications• Direct manipulation
[Lewis and Anjyo 2010] with local influence
• Cage deformation
Compression and Direct Manipulation of Complex Blendshape Models
Matrix Size Dense Sparse PCA Local PCA HSS HSS+Banded
Character # Rows # Cols MB % MB % MB % MB % MB % MB %
Dumb 127173 730 354 100% 348 98.3% 138.7 39.2% 87.4 24.7% 46.8 13.2% 25.4 7.2%
Dumber 155187 625 370 100% 317 85.7% 164.6 44.5% 104.7 28.3% 46 12.4% 28.1 7.6%
Armadillo 106289 284 115.2 100% 173.2 150.3% 114.8 99.7% 10.4 9.0% 8.6 7.5%
τ=1e-2 for PCA, τ=1e-3 for HSS
ResultsMemory
Speed (in milliseconds) Sparse HSS HSS+Banded
Character 8 CPUs 8 CPUs GPU 8 CPUs GPU
Dumb 124.21 11.22 1.47 10.73 2.18
Dumber 113.65 11.01 1.41 10.76 2.12
Armadillo 28.78 3.62 0.82 4.22 1.18
Controlling Physics-Based Characters Using
Soft ContactsSumit Jain and C. Karen Liu
Georgia Institute of Technology
Controlling Physics-Based Characters Using Soft Contacts
Motivation
VIDEO
Controlling Physics-Based Characters Using Soft Contacts
Contributions• Coupling of articulated rigid body and soft
body with practical contact model
• Experiments to show soft contact model stabilizes physically simulated characters
Controlling Physics-Based Characters Using Soft Contacts
Coupled Dynamics• Articulated rigid body
Massmatrix
Coriolismatrix
Gravity Generalizedforces
Jacobianat contact
Contactforce
Controlling Physics-Based Characters Using Soft Contacts
• Deformable bodyo Vertex deformation – tries to keep vertices at their rest positions
o Edge deformation – tries to keep the relative positions of the vertices
Coupled Dynamics
Stiffnessmatrix
Dampingmatrix
Controlling Physics-Based Characters Using Soft Contacts
Coupled Dynamics• Rigid + Deformable
• Adaptive deformable modelo P-ring neighborhood of contact points are
simulated, rest are treated as rigido Mass matrix is pre-computed at the rest positions
Controlling Physics-Based Characters Using Soft Contacts
Coupled Dynamics• Discretize with time step h
Controlling Physics-Based Characters Using Soft Contacts
Contact Model• Contact with friction as Linear Complementarity
Problem (LCP) [Anitescu and Potra 1997]o Advantages over penalty-based methods:
• Enforces work-less normal force, no penetration, and realistic slipping
• Explicit deformation at contact increases contact points• Low stiffness in penalty methods causes frequent penetration
Controlling Physics-Based Characters Using Soft Contacts
Locomotion Control:SIMBICON
1. Compute joint torque τs
2. Detect collisions3. Create contacts to be solved for in ODE4. Apply τs to character in ODE
5. Advance one time step in ODE to get next state
Controlling Physics-Based Characters Using Soft Contacts
Locomotion Control:SIMBICON + Proposed Method
1. Compute joint torque τs
2. Detect collisions3. Create contacts to be solved for in ODE
a. Convert τs to generalized torques τr
b. Convert state to generalized coordinatesc. Solve (qk+1, qk+1) and fc using LCP
d. Apply fc to character in ODE
4. Apply τs to character in ODE
5. Advance one time step in ODE to get next state
Modal-Space Control for Articulated
CharactersSumit Jain and C. Karen Liu
Georgia Institute of Technology
Modal-Space Control for Articulated Characters
MotivationArbitrary character simulation with both• long-term (anticipatory) planning• short-term (reactive) planningis prohibitively expensive to compute
?External
force
Modal-Space Control for Articulated Characters
ContributionFormulation of modal-space character control capable of long-term planning and frequent re-planning for simulating“specific motion sequence”
Modal analysis provides:• Independent control: N-dimensional optimization to N
independent one dimensional problems• Model reduction: Allows construction of a small number of
strategies specific to certain frequencies of the dynamic system
Modal-Space Control for Articulated Characters
Modal Analysis
Md and Kd are diagonal, thus
N independent 1d problems
Modal-Space Control for Articulated Characters
Strategy For Modes1. Rigid modes (zero frequency)
o Corresponds to six eigenvectors in Φ with zero eigenvalueso Only affected by external forceso For long term planning
2. Low frequency modeso Corresponds to eigenvectors with
eigenvalues smaller than some thresholdo Visibly significant movements
by actuated system(see right)o For long term planning
3. High frequency modeso Less visually significanto For reactive planning
1st three principal componentsdominated by low frequency
Modal-Space Control for Articulated Characters
Control Summary2. Low frequency
modes: estimate joint actuationo Solve unconstrained QP for
ideal actuation Ia* to match low frequency reference state
1. Rigid body modes: estimate contact forceso Solve QP, constrained by
Coulomb friction, for ideal contact forces f* to match rigid mode reference state
Modal-Space Control for Articulated Characters
Control Summary4. Corrective forces
o Δf and ΔIa are computed to satisfy Coulomb friction
3. High frequency modes: track short-horizon plano Analytically compute high-
frequency actuation to match reference state
Modal-Space Control for Articulated Characters
Results
VIDEO
Stretchable and Twistable Bones for Skeletal Shape
DeformationAlec Jacobson∗ and Olga Sorkine†
∗New York University, †ETH Zurich
Stretchable and Twistable Bones for Skeletal Shape Deformation
Motivation• Conventional bone skinning methods cause
unnatural deformation at the end of bones when scaled
Stretchable and Twistable Bones for Skeletal Shape Deformation
Linear Blend Skinning (LBS)
• Weight for each bone
Resultingposition
Weight foreach bone
Rotation
Scale Originalposition
Stretchable and Twistable Bones for Skeletal Shape Deformation
Stretchable, Twistable Bones Skinning
(STBS) • Weight for each bone and endpoint
o Naturally extends to use dual quaternion
Twist alongbone
Weight foreach endpoint
Stretchable and Twistable Bones for Skeletal Shape Deformation
Results
Stretchable and Twistable Bones for Skeletal Shape Deformation
• Manually paint• Automatic
o Bone Heat [Baran and Popovic 2007]o Bounded Biharmonic Weight [Jacobson et al. 2011]
Generating Weights
Stretchable and Twistable Bones for Skeletal Shape Deformation
Comparison:BH vs. BBW