MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Motion Pattern Preserving IK
Operating in the Motion Principal Coefficients Space
Schubert R. Carvalho, Ronan Boulic and Daniel Thalmann
Presented by Schubert R. Carvalho
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Overview
•
•
•
•
•
Introduction
Related Work
A Model for Editing
Experiments
Conclusions and Future Work
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Introduction
1
• Challenges of Motion Editing
Techniques
– Preserve the characteristics of
the original animation
– Impose continuity between
frames
• Motivation
– How to edit a motion by
constraining just one pose
without adding discontinuities?
2
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Related work
• Traditional Motion Editing
• [Lee et. al. 1999]
• [Gleicher 2001]
• [Kulpa 2005]
• [Le Callennec and Boulic 2006]
• [Liu et. al. 2006]
• Principal Component Analysis in Computer
Animation
• [Alexa and Müller 2000]
• [Safanova et. al. 2004]
• [Glardon et. al. 2004]
• [Urtasun and Fua 2004]
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
A Model for Editing
• Three basic issues
– Motion Parameterization
– Constraining a Single Posture in the Motion PC
Space
– Impose Continuity
WSCG 2007
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Motion Parameterization
• Principal Components Analysis (PCA)
Ψ1, Ψ2 , ..., ΨM
Pose
ΨM = [Θt , ..., Θt , ..., Θt ]
0
Motion
Database
k
PCA
1
PC
PCs
0≤ k ≤ 1
Θt = [Φ1, P1, Φj, ..., Φn]
k
root
Joints
angles
m
ΨD ≈ Ψo + ∑αDiEi
I=1
m≤M
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
WSCG 2007
Constraining Formulation
• Constraining a Single Pose in the Motion PC
Space
Δα = J(α)tεΔx
p=3; m=8; n=93; D=12276
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Imposing Continuity
• Continuity is enforced through the PCA parameters.
Algorithm’s Convergence
While not converged do
k
ε
1: Δα J(α)t Δx
2: αD
3: ΘD
αD + ΔαD
Ψot + αDEtk
k
end while
4: ΨD
PC (Et )
m
Ψo + ∑ αDi Ei
I=1
Time (s)
Nb. Of Iterations
2
40000
19196
3
110000
50214
4
42000
19929
5
9000
4194
6
1625
757
7
0.500
235
8
0.484
221
9
0.531
247
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Experiments: Editing and Style (1)
1
2
Input Motion
0
2
-4
-3
-2
-1
1
3
4
5
-5
2nd Component
3
4
5
Golf Swing Database
-5
0
5
10
15
20
25
1st Component
30
35
40
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
WSCG 2007
Experiments: Editing and Style (2)
damping = 10; num. of iterations = 150
tracked error = 0.01m.
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Experiments: Visual Comparison (1)
f = 93
f = 94
WSCG 2007
WSCG 2007
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Experiments: Visual Comparison (2)
PIK
N. of Constraints
Fr. Constrained
Presented Artifacts
Computation Time
5
11
Our Approach
1
1
Feet Sliding, Balance and
Arms’ Inter Penetration
Nothing
Detected
1 sec.
100 sec.
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
WSCG 2007
Conclusions
• If the motion needs just an adjustment of one key
event, our approach can provide faster and more
realistic results than current approaches.
• Our approach provided quality results with less
tuning from the user side.
Future work
• Extend the current method to treat multiple
constraints.
• Extend the current method to constrain multiple
frames (if necessary).
MOTION PATTERN PRESERVING IK OPERATING IN THE MOTION PRINCIPAL COEFFICIENTS SPACE
Thanks four your attention!
WSCG 2007