Hair and strand-like deformable models

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Hair and strand-like deformable models

• 15-863 Class 15 (Mar 11)
• Doug James, CMU

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OverviewClass 15 (Mar 11)

• Course project proposal
• Strand-like deformable models
• Hair, sutures, cables, and other 1D structures
• Flexible chains
• geometrically large deformation
• Twist DOF makes things more interesting

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Project Proposal

• 2 pages or less
• Use SIGGRAPH style LaTeX formatting
• http//www.siggraph.org/publications/instructions
• Proposal section structure
• Abstract
• Introduction (What, why, related work)
• Details of approach
• Proposed work (incrementally defined)
• Will do (core material)
• Hope to do (time-permitting)
• Ultimately would like to do (if 1 2 get done)
• Summary of proposed contributions
• References (e.g., use BibTeX graphbib)

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Project Calendar

• Proposal Thursday, March 20.
• Progress report Tuesday, April 15.
• Presentation Thursday, April 24(?)
• Final report Tuesday, April 29.
• ACM I3D Away Tu-April 29 Th-May 1.

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Project Software

• Dont have to reinvent the wheel
• Can explore PBMIS applications versus modeling
  fundamentals
• FEM, BEM, rigid bodies, collision detection, my
  code, etc.
• Constraint project must be substantial

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Possible evaluation choice

• OPTION A
• 30 - 2 assignments
• 60 - project
• 10 - presentation

• OPTION B
• 45 - 3 assignments
• 45 - project
• 10 - presentation

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Strand-like deformable models

• Hair, sutures, cables, and other 1D structures
• Flexible chains
• geometrically large deformation
• Twist DOF makes things more interesting
• Application determines utility of physically
  based models

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Interactive Multiresolution Hair Modeling and
EditingTae-Yong Kim, Ulrich Neumann.ACM
Transactions on Graphics. 21(3), pp. 620-629,
2002.

• Sometimes physics just gets in the way
• Hairstyling doesnt require physically accurate
  hair
• Good survey
• N.Magnenat-Thalmann, S.Hadap, P.Kalra, State of
  the Art in Hair Simulation, International
  Workshop on Human Modeling and Animation, Seoul,
  Korea, Korea Computer Graphics Society, pp. 3-9,
  June, 2002.

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Interactive Multiresolution Hair Modeling and
EditingTae-Yong Kim, Ulrich Neumann.ACM
Transactions on Graphics. 21(3), pp. 620-629,
2002.
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Faking Dynamics of Ropes and SpringsRonen
Barzel.IEEE Computer Graphics Applications.
17(3), pp. 31-39, 1997.

• Animator key frames amplitudes of shape functions

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Faking Dynamics of Ropes and SpringsRonen
Barzel.IEEE Computer Graphics Applications.
17(3), pp. 31-39, 1997.
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Faking Dynamics of Ropes and SpringsRonen
Barzel.IEEE Computer Graphics Applications.
17(3), pp. 31-39, 1997.
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Recall...
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Some other approaches

• Could add torsional springs
• Rosenblum et al. 91
• Daldegan et al. 93
• Simulated Knot Tying. J.M. Phillips, A.M. Ladd,
  L.E. Kavraki. IEEE International Conference on
  Robotics and Automation 2002.
• See webpage for more examples.

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Open Kinematic Chains

• Hair is basically inextensible
• ? numerical stiffness
• Multibody open chain approx. is now common for
  hair
• Can be solved efficiently
• Articulated-Body Method
• Reduced coordinate formulation
• O(n) forward dynamics
• Featherstone, R., Robot Dynamics Algorithms,
  Kluwer, Boston, 1987.
• Could (of course) use fast O(n) Lagrange
  multiplier methods

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A Practical Model for Hair Mutual
InteractionsJohnny T. Chang, Jingyi Jin, Yizhou
Yu.ACM SIGGRAPH Symp. on Computer Animation. pp.
73-80, 2002.

• Recent example
• Static links
• Hair-hair interactions
• Hair interpolated using guide hairs
• Use Featherstones algorithm

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A Practical Model for Hair Mutual
InteractionsJohnny T. Chang, Jingyi Jin, Yizhou
Yu.ACM SIGGRAPH Symp. on Computer Animation. pp.
73-80, 2002.
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A Practical Model for Hair Mutual
InteractionsJohnny T. Chang, Jingyi Jin, Yizhou
Yu.ACM SIGGRAPH Symp. on Computer Animation. pp.
73-80, 2002.
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A Practical Model for Hair Mutual
InteractionsJohnny T. Chang, Jingyi Jin, Yizhou
Yu.ACM SIGGRAPH Symp. on Computer Animation. pp.
73-80, 2002.
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A Practical Model for Hair Mutual
InteractionsJohnny T. Chang, Jingyi Jin, Yizhou
Yu.ACM SIGGRAPH Symp. on Computer Animation. pp.
73-80, 2002.
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Eric Plante, Marie-Paule Cani, Pierre Poulin,
Capturing the Complexity of Hair Motion, GMOD
numéro 1 volume 64 , january 2002.
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Next class...

• Thursday, March 13
• Fast and Flexible 3D Scanning
• Szymon Rusinkiewicz, Princeton University
• Wean Hall 4623, Talk 1230pm - 200pm
• The digitization of the 3D shape of real objects
  is a rapidly expanding field, with applications
  in design,
• manufacturing, and mapping spaces such as
  buildings and caves. This talk will describe
  recent
• research aimed at increasing the speed and
  flexibility of 3D scanning systems. Two new
  scanner
• designs will be presented, one based on active
  temporal stereo and the other based on projected
• structured light with stripe boundary coding.
  Both are based on a space-time stereo framework,
  in
• which correspondences between two cameras or
  between a camera and projector are obtained by
• considering windows with extent in both space and
  time. The scanners are the first stage in a 3D
• model acquisition pipeline, which also includes
  algorithms for aligning and merging successive
  range
• images. The talk will discuss the value of having
  the entire pipeline operate in real time, which
  allows
• the user to see holes in the model and determine
  when the object has been completely covered.
• Results are presented from a prototype that
  incorporates 60 Hz. structured-light rangefinder,
  a real-

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D. K. Pai, STRANDS Interactive Simulation of
Thin Solids using Cosserat Models,Computer
Graphics Forum, 21(3), pp. 347-352, 2002.