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Modeling and Animating Eye Blinks. Laura Trutoiu, Liz Carter, Iain Matthews, Jessica Hodgins. What is an eye blink?. Eye blinks: Common wisdom. "... five frames is usually adequate for most situations, although four frames can make a character look more alert." - PowerPoint PPT Presentation
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Modeling and Animating Eye Blinks
Laura Trutoiu, Liz Carter, Iain Matthews, Jessica Hodgins
What is an eye blink?
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Figure adapted from “Digital Character Animation”, Maestri,G . New Riders Publishing. 1996
Eye blinks: Common wisdom"... five frames is usually adequate for most situations, although four frames can make a character look more alert."
The Animator's Survival Kit by Richard Williams, Faber and Faber, NYC, 2001.
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Figure adapted from “Digital Character Animation”, Maestri,G . New Riders Publishing. 1996
Eye blinks: Common wisdom"... five frames is usually adequate for most situations, although four frames can make a character look more alert."
The Animator's Survival Kit by Richard Williams, Faber and Faber, NYC, 2001.
Frame (24fps)
Inte
r-eyelid
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tance
Eye Blinks: What can we see?‣Temporal asymmetry:
‣Fast closing, slow opening
‣Closing amplitude:‣Eyes may not fully close
‣Variety:‣Varying duration & closing amplitude
‣Lower eyelid motionQuickTime™ and a
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Eye blinks: Can you tell the difference?
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Video 2:Video 1:
Eye blinks show temporal asymmetry and you can tell the difference.
forward backward
Eyes alive. LEE, S., BADLER, J., AND BADLER, N. ACM Trans. on Graphics 21, 3, 637–644. 2002.Automated eye motion using texture synthesis. DENG Z., LEWIS J. P., NEUMANN U. IEEE Computer Graphics and Applications 25, 2, 24– 30, 2005Eyelid kinematics for virtual characters. STEPTOE, W., OYEKOYA, O., AND STEED, A. Comput. Animat. Virtual Worlds 21 (May), 161–171. 2010
Related work: Eyes in graphicsEyes alive [Lee 2002]
eye gaze/saccades only
Eye motion with texture synthesis [Deng 2005]
no explicit eye blink modelrequires training
Eyelid kinematics [Steptoe 2010]parametric models for eyelid saccades and eye blinks using current position
10 participants
How do we create more natural eye-blink animations?
Track high speed video of eye blinks
Build a generative model that closely resembles the tracked data
Validate the model through perceptual experimentsWhy simple approximations are not good enough
Tracking eye blinksActor performance
Emotional vignettes and in-between pauses
High speed videoCasio Exilim F1 - 300 fps
Video trackingActive Appearance Models (AAMs) [Matthews 2004]
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Active appearance models revisited. Matthews, I. and Baker, S. International Journal of Computer Vision 60, 2, 135–164. 2004
Tracking eye blinks
Eye blink time series Normalized time series
Generated Data Re-timed data
Principal Component Analysis
Video = unobtrusive way to measure eye blink dynamicsHigh speed video => temporal resolution
Building a generative model
Perceptual experimentsQuickTime™ and a
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Can naive users differentiate between different eye blink dynamics?
Stimuli:Animations at 30 fps
Role of appearance:photorealistic and cartoon character
Naturalness rating (1-7)Very natural clip (7) = “what you would expect to see in the real world”
Perceptual experiments
Perceptual experiments
Exp 1: Model vs. real blinks
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1 2
3 4
Model, fully closed
Real, fully closed
Model, naturally closed
Real, naturally closed
Model vs. real + Closing amplitude
Exp 1: Model vs. real blinks
Natu
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Real Model
n = 32, 2 (character) x 2 (profiles) x 2 (blur) x 2 (amplitude) repeated-measures ANOVA
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Real
Model
300 fps
p < 0.001*
Exp 1: Model vs. real blinks
n = 32, 2 (character) x 2 (profiles) x 2 (blur) x 2 (amplitude) repeated-measures ANOVA
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Modelnaturally closed
Modelfully closed
300 fps
Natu
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Naturally closed
Fully closed
Perceptual experiments
Photorealistic > Cartoon
Fully closed > Naturally closed
Perceptual experiments
Photorealistic > Cartoon
Fully closed > Naturally closed
Exp 2: Model vs. Approximations
Model
Linear Symmetric
Linear Asymmetric
Ease In/Ease OutSymmetric
Ease In/Ease OutAsymmetric
Hypothesis: Asymmetric > Symmetric, Non-linear > Linear
Exp 2: Model vs. approximations
2 3
4 5
Model
Symmetric ease-in/ ease-out
Asymmetric linear
Symmetric linear
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Asymmetric ease-in/ ease-out
1
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Exp 2: Model vs. approximations
n = 43, 5 (profiles) x 4 (length) x 2 (character) repeated-measures ANOVA
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Perceptual experiments
Photorealistic > Cartoon
Fully closed > Naturally closed
Model > Approximations
Not symmetric: More time to open than to close Animation textbook - same number of frames for opening
and closing
Not linear: Fast closing (linear velocity) followed by slowly converging
opening Animation - linear or slowly accelerating, slowly decelerating
Eyes may not fully close: At least 50% of the time Animation - eyes always fully close In our experiments, fully closed animations preferred
?
Conclusions: Eye blinks are ...
Future work
Sequences of eye blinksinter-blink distancevariability may be useful
Synchronization with other facial motion
Blink sequence patterns
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Exp 3: Lower eyelid motion
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Vertical only
Vertical + Horizontal
Horizontal only
No Lower eyelid motion
Exp 3: Lower eyelid motion
n = 32, 4 (lower eyelid motion) x 1 repeated-measures ANOVA
Horizontal+ Vertical
No HorizontalNo Vertical
Horizontal Vertical