Motion Synthesis from Annotations

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Motion Synthesis from Annotations
Okan Arikan, David A. Forsyth, James F.
OBrien University of California, Berkeley
November 9, 2006 - Presented by Ji Hyeon Yi -
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Contents

• Introduction
• Related Work
• Annotating Motions
• Motion Specification
• Motion Synthesis
• Results
• Conclusion

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Introduction

• Provide animators with intuitive controls for
  synthesizing motions
• annotations constraints ? synthesizes new motion

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Related Work

• Example based motion synthesis
• Arikan and Forsyth 2002 Lee et al. 2002 Li et
  al. 2002 Pullen and Bregler 2002 Molina-Tanco
  and Hilton 2000
• Motion graphKovar et al. 2002a
• Motion control
• Blumberg and Galyean 1995 Mataric 2000
  Grzeszczuk and Terzopoulos 1995 Perlin and
  Goldberg 1996
• Etc
• Verb graphRose et al. 1998
• Physically based methodsWitkin and Kass 1988
  Liu and Popovic 2002 Hodgins et al. 1995
  Faloutsos et al. 2001

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Overview

• Annotating Motions
• Motion specification
• Motion synthesis
• Optimization
• Practical Algorithm
• Creating the Motion

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Annotating Motions

• Annotations
• Describe motions and reflect database
• Actions (stand, walk, run, ) modifiers (reach,
  catch, carry, )
• Flexible vocabulary
• Can be combined
• Semiautomatic process
• SVM classifier for each annotation
• Binary group 1 or group -1
• Coordinate vector
• Joint positions for one second of motion centered
  at the frame being classified in the torso
  coordinate system

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Motion Specification

• Specify constraints
• Annotation constraints
• Positively, negatively, dont-care
• Length constraints
• Continuity constraints
• Frame constraints
• Position constraints

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Optimization
,
optimization
Reduced feature vector
Dynamic Programming
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Practical Algorithm

• Multi resolution DP
• Capture the essential structure at the coarse
  level
• 32 frame blocks
• Refinement at finer level
• 16 frame blocks
• 8 frame blocks
• Clustering and active set
• Search time
• Frame constraints

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Position Constraints

• Position constraints
• Combinations of motions
• Cuts at the 8 frame block granularity
• Add to DP score how close the motion gets to the
  desired position
• The pool of best 20 motions for each level

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Creating the Motion

• May be discontinuous at the block boundaries
• Tweaks boundaries using local minimization

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Results

• video

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Conclusion

• Synthesized motions that match given annotations
  and other constraints using multi resolution DP
• Interactive search
• Inability to synthesize frames not in the
  database
• No explicitly computed motion graph

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Support Vector Machine

• Determine the hyperplane between two classes
  from training set

• Linear
• Non-linear

Kernel function