Remeshing forFEM Analysisof Viscous Objects

CPSC 524 Final Project

Tricia Pang, Kyle Porter, Josna Rao

January 8, 2008

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Outline

Introduction

Dataset

Method

Results

Discussion

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Introduction FEM analysis of viscous objects

Useful for modeling food bolus on tongue in human oral cavity

Mark A. Nicosia. “Planar Finite Element Modeling of Bolus Containment in the Oral Cavity.” Computers in Biology & Medicine, 2007.Screenshot from Artisynth Toolkit

Food bolus

Tongue surface

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Introduction Problems result from large physical deformations

Triangle mesh uniformity disrupted Poor distribution of physical properties (node mass/velocity)

Further deformation requires well-conditioned meshes

Mark A. Nicosia. “Planar Finite Element Modeling of Bolus Containment in the Oral Cavity.” Computers in Biology & Medicine, 2007.

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Project Goal Remesh viscous model after high deformation

User-defined level of detail (number of vertices) Good triangle uniformity Preserve geometry

Extension: execute topological changes when required Eg. Mesh splitting

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Dataset Generate in Artisynth

Java-based 3D biomechanical modelling toolkit Physical simulation using FEM mechanics Node connectivity described by tetrahedrons

Replicate high-viscosity by setting material property Simulate physical deformations until failure

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Method Explicit surface remeshing (Surazhsky and Gotsman, 2003)

2D remeshing using local parameterizations Adjust vertices to maximize angles of triangles in mesh Use error metrics to ensure mesh fidelity Reference current mesh to original mesh

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Method Adjust number of vertices

Alternate between edge splits/collapses and area-based remeshing

Area-based remeshing Local 2D parameterizations Relocate vertices in current mesh Improve angles of incident triangles for each neighbourhood Measure error between new mesh and original mesh

Delaunay edge flips

Regularize connectivity Obtain ideal valence for each vertex

Angle-based smoothing

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Method Overlapping Parameterization

Patch parameterization scheme for performing local operations

Patches stored and reused

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Method Extension: Mesh Splitting

Execute when “bottleneck” occurs Method #1: Principal curvature

Method #2: Medial axis

No working implementation for project

Kmin < 0

Kmax > 0

x

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Results

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Results

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Discussion High triangle uniformity in final meshes

Limitation of method:

Sharp features sometimes not preserved

More fine-tuning of error metrics

Limited dataset

Could not reproduce highly-deformed meshes in Artisynth because poor mesh quality results in deformation failure

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References V. Surazhsky and C. Gotsman. Explicit Surface Remeshing.

Eurographics Symposium on Geometry Processing, pages 17–28, 2003.

V. Surazhsky and C. Gotsman. High quality compatible triangulations. Proceedings of 11th International Meshing Roundtable, pages 183-192, Sept. 2002.

S. Fels, F. Vogt, K. van den Doel, J. Lloyd, I. Stavness and E. Vatikiotis-Bateson. Developing Physically-Based, Dynamic Vocal Tract Models using ArtiSynth. Proc. Int. Seminar Speech Production, pages 419-426, 2006.

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Questions?