Hair and strand-like deformable models 15-863: Class #15 (Mar 11) Doug James, CMU.

Hair and strand-like deformable models

15-863: Class #15 (Mar 11)

Doug James, CMU

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

Project Proposal

• 2 pages or less• Use SIGGRAPH style LaTeX formatting

• http://www.siggraph.org/publications/instructions

• Proposal section structure:1. Abstract2. Introduction (What, why, related work)3. Details of approach4. Proposed work (incrementally defined)

1. Will do (core material)2. Hope to do (time-permitting)3. Ultimately would like to do (if 1 & 2 get done)

5. Summary of proposed contributions6. References (e.g., use BibTeX & graphbib)

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.

Project Software

• Don’t 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

Possible evaluation choice

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

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

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

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 doesn’t 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.

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

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

• Animator key frames amplitudes of shape functions

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

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

Recall...

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.

From [Hadap and Magnenat-Thalmann 01]

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

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 Featherstone’s algorithm

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

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

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

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

Eric Plante, Marie-Paule Cani, Pierre Poulin, Capturing the Complexity of Hair Motion, GMOD numéro 1 volume 64 , january 2002.

Next class...Thursday, March 13

Fast and Flexible 3D Scanning

Szymon Rusinkiewicz, Princeton University

Wean Hall 4623, Talk 12:30pm - 2:00pm

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-time variant of ICP (iterative closest points) for alignment, and point-based merging and rendering algorithms.

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