GAIT ANIMATION AND ANALYSIS FOR BIOMECHANICALLY ARTICULATED SKELETONS ERIC ...

307 Pages·2008·18.72 MB·English

GAIT ANIMATION AND ANALYSIS FOR BIOMECHANICALLY­
ARTICULATED SKELETONS

by

ERIC DAVID WILLS

A DISSERTATION

Presented to the Department of Computer and Information Science

and the Graduate School of the University of Oregon

in partial fulfillment of the requirements

for the degree of

Doctor of Philosophy

March 2008
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University of Oregon Graduate School

Confirmation of Approval and Acceptance of Dissertation prepared by:

Eric Wills
Title:
"Gait Animation and Analysis for Biomechanically-Articulated Skeletons"
This dissertation has been accepted and approved in partial fulfillment ofthe
requirements for the Doctor ofPhilosophy degree in the Department of Computer &
Information Science by:
Kent Stevens, Chairperson, Computer & Information Science
Arthur Farley, Member, Computer & Information Science
Christopher Wilson, Member, Computer & Information Science
Gregory Retallack, Outside Member, Geological Sciences
and Richard Linton, Vice President for Research and Graduate StudieslDean of the
Graduate School for the University of Oregon.
March 22, 2008
Original approval signatures are on file with the Graduate School and the University of
Oregon Libraries.
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© 2008 Eric David Wills
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An Abstract of the Dissertation of
Eric David Wills for the degree of Doctor of Philosophy
in the Department of Computer and Information Science to be taken March 2008
Title: GAIT ANIMATION AND ANALYSIS FOR BIOMECHANICALLY­
ARTICULATED SKELETONS
Approved:
Kent A. Stevens
Digital three-dimensional (3D) models are useful for biomechanical analysis
because they can be interactively visualized and manipulated. Synthesizing and
analyzing animal locomotion with these models, however, is difficult due to the large
number ofjoints in a fully articulated skeleton, the complexity of the individual joints, and
the huge space of possible configurations, or poses, of the skeleton taken as a whole. A
joint may be capable of several biological movements, each represented by a degree of
freedom (DOF). A quadrupedal model may require up to 100 DOFs to represent the
limbs and tnmk segments only, resulting in extremely large spaces of possible body
configurations. New methods are presented here that allow limbs with any number of
biomechanical DOFs to be kinematically exercised and mapped into a visualization
space. The spaces corresponding to the ranges of motion of the left and right limbs are
automatically intersected and pruned using biological and locomotion constraints. Hind
v
and fore spaces are similarly constrained so that Genetic Algorithms (GAs) can be used
to quickly find smooth, and therefore plausible, kinematic quadrupedal locomotion paths
through the spaces. Gaits generated for generic dog and reptile models are compared to
published gait data to determine the viability of kinematics-only gait generation and
analysis; gaits generated for Apatosaurus, Triceratops, and Tyrannosaurus dinosaur
models are then compared to those generated for the extant animals. These methods are
used for several case studies across the models including: isolating scapulothorax and
shoulder joint functionality during locomotion, determining optimal ankle heights for
locomotion, and evaluating the effect of limb phase parameters on quadrupedal
locomotion.
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CURRICULUM VITAE
NAME OF AUTHOR: Eric David Wills
PLACE OF BIRTH: Santa Monica, CA, USA
DATE OF BIRTH: November 19, 1977
GRADUATE AND UNDERGRADUATE SCHOOLS ATTENDED:
University of Oregon, Eugene, OR USA
DEGREES AWARDED:
Doctor of Philosophy in Computer and Information Science, 2008,
University of Oregon
Master of Science in Computer and Information Science, 2002,
University of Oregon
Bachelor of Science in Computer and Information SciencelMathematics, 2000,
University ofOregon
AREAS OF SPECIAL INTEREST:
Evolutionary Locomotion Synthesis

Computational Biomechanics

Computer Graphics and Animation

Parallel and Distributed Computing

PROFESSIONAL EXPERIENCE:
Principal Engineer, Kaibridge, Inc., 5 years

Software Engineer, Integrated Measurement Systems, 3 years
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GRANTS, AWARDS AND HONORS:
Graduate Teaching Fellow of the Year, Department of Computer and Information
Science, University of Oregon, 2005
Inducted into Upsilon Pi Epsilon, International Honor Society for the Computer
and Information Disciplines, 2003
Departmental Honors for completion of an honors thesis, Department of
Computer and Information Science, University of Oregon, 2000
PUBLICATIONS:
Stevens, K. A., Larson, P., Wills, E. D., & Andersen, A. (2008). Rex, sit: Digital
modeling of Tyrannosaurus rex at rest. In P. Larson & K. Carpenter (Eds.),
Tyrannosaurus rex: The tyrant king. Bloomington, IN: Indiana University Press.
Stevens, K. A., & Wills, E. D. (2007). Kinematic constraints on the reconstruction of
Dinosaur gaits. Proceedings ofthe Symposium on Vertebrate Paleontology and
Comparative Anatomy, 55,54.
Wills, E. D., & Stevens, K. A. (2007). Computational explorations of quadrupedal
locomotion in Dinosaurs based on modem analogs. Proceedings ofthe American
Society ofBiomechanics Northwest Symposium, 3, 18.
Wills, E. D., & Stevens, K. A. (2007). Isolating functional degrees of freedom in limbs
during locomotion. Proceedings ofthe Symposium on Vertebrate Paleontology
and Comparative Anatomy, 55,46.
Stevens, K. A., Wills, E. D., & Ernst, S. W. (2006). 3D Visualization of allometric
changes in whole skeletons: Posture, proportion, and range of motion. Journal of
Vertebrate Paleontology, 26(Suppl. 3A), 128.
Stevens, K. A., Parrish, J. M., & Wills, E. D. (2005). Ontogenetic changes within the
tyrannosaurid skeleton. In R. Scherer (Chair), Tyrannosaur Symposium 2005.
Symposium conducted at the Burpee Museum of Natural History, Rockford, IL.
Stevens, K. A., & Wills, E. D. (2001). Gracile versus robust cervical vertebral designs in
sauropods. Journal of Vertebrate Paleontology, 21(Suppl. 3A), 104.
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ACKNOWLEDGEMENTS
I would like to express my sincere appreciation to my family and friends for their
support and advice throughout this process. Specifically, I would like to thank my caring
parents Dr. David and Laurie Wills, my dedicated and entertaining sister Dr. Megan
Wills Kullnat, and especially my loving, understanding, and beautiful wife Shelby Stair
Wills. I would like to thank my committee for their guidance and expertise, especially
Professor Kent A. Stevens, whose focused attention and patience over the last decade
have shaped me into the professional that I am today. This work was supported in part by
National Science Foundation grant 0093929.
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To my family and friends.
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TABLE OF CONTENTS
Chapter Page
I. INTRODUCTION 1

II. BACKGROUND AND RELATED WORK 9

Automatic Character Animation 11

Global Optimization 11

Local Controllers 21

Fragment Composition 31

Evolutionary Algorithms 41

Evolutionary Locomotion 45

Controller Evolution 46

Artificial Life 59

Robotics 69

Computational Gait Analysis 76

Summary 92

III. METHODS AND MATERIALS 95

Functional Degrees ofFreedom 95

Limb Ranges ofMotion 97

Bipedal Gait Reconstruction 101

Constraints 101

Reconstruction 107

Pipeline 115

Quadrupedal Gait Reconstruction 117

Constraints 117

Reconstruction 120

Pipeline 124

Gait Refinement. 126

Trackway Visualization 128

Scaling Model Elements 129

Models 129

Dog 130