ANATOMIC MODELING OF HUMAN BODIES USING PHYSICALLY-BASED MUSCLE

126 Pages·2001·1.47 MB·English

ANATOMIC MODELING OF HUMAN BODIES USING
PHYSICALLY-BASED MUSCLE SIMULATION
THÈSE No 0000 (1998)
PRESENTÉE AU DÉPARTEMENT D’INFORMATIQUE
ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE
POUR L’OBTENTION DU GRADE DE DOCTEUR ÈS SCIENCES
PAR
LUCIANA PORCHER NEDEL
MSc. In Computer Science, Federal University of Rio Grande do Sul, Brésil
de nationalité brésilienne
Lausanne, EPFL
1998
“You will make nothing but confusion in your
demonstration of the muscles and their positions,
beginnings and ends, unless first you make a demonstration
of the fine muscles by means of threads; and in this way you
will be able to represent them one above another as nature
has placed them; and so you will be able to name them
according to the member that they serve, that is, the mover
of the point of the big toe, and of the middle bone, or the
first bone, etc.
And after you have given these details you will show at the
side the exact shape and size and position of each muscle;
but remember to make the threads that denote the muscles
in the same positions as the central lines of each muscle and
in this way these threads will show the shape of the leg and
their distance in rapid movement and in repose.”
Leonardo da Vinci (1452-1519)
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Acknowledgments
First, I would like to thank my Thesis supervisor Prof. Daniel Thalmann for his
invaluable guidance and support. Many thanks also to Dr. Ronan Boulic for his help,
interest and collaboration during this research.
I would like to thank all the members of LIG for their collaboration, specially Thierry
Michellod for his interest and dedication to the design of the human body, Walter Maurel
for his suggestions and our fruitful discussions, Olivier Paillet for the design of the Body
Builder Plus interface, Jianhua Shen for the work on the development of Body Builder,
Ronan Boulic, Ik Soo Lim and Marcelo Kallmann for the manuscript review, Nathalie
Farenc for the abstract’s translation to French and for the informations exchanged about
Open Inventor libraries, Selim Balcisoy and Mireille Clavien for their help with video
equipment and Tom Molet for the help and support with the use of Bodylib. I would like
to thank also the colleagues Joaquim Esmerado, Marcelo Kallmann, Nathalie Farenc,
Soraia Musse, Elsa Schweiss, Cédric Delon, Tolga Çapin, Srikanth Bandi, Maja Jovovic,
Christian Miccio, Amaury Aubel and Luc Emering for their constant encouragement on
the last days. A special thanks also to Josiane Bottarelli, the secretary of LIG, for her
availability and precious help.
I would like to thank also the staff of MIRALab, especially Prof. Nadia Thalmann for
their collaboration and support.
Many, many thanks to my husband Niuton Zinn Severo for his invaluable support and
love and for the sacrifice of three years and a half of his own professional career to stay
with me in Switzerland. I also extend my thanks to all my family, mainly my parents and
sisters, for the encouragement and especially my mother for the hundreds of daily e-mails
that have helped to reduce the distance…
I would like to thank some friends that were very near (in reality or virtually) during this
3.5 years of “exile”: Val, Xuxu, Bruno, Rafa, Tila, Timo, Gérson, Lucianinha, Soraia,
Milton, Dê Bande, Rogério, Nara, Paulo, Sílvia, Vera and Cléo. Finally a would like to
thank all the friends in Lausanne for having, in same way, replaced my family: Paulo,
Elsa, Rafael, Rebeca, Raquel, Carlinhos, Fátima, João, Arturzinho, Chiquinha, Leandro,
Cristina, Luana, Liz, Viviane, Eytan, Pedro, Gabriel, Márcio, Rita, Mariana, André,
Alexandre, Leni, Olivier, Aroldo, Soraia, Milton, Diógenes, Lucia, Igor, Ivan, José Paulo,
Marcelo, Suzane, Pedone, Cecília, Joca, Nathalie, Manú, Nabih, Nezha, Amane, Kenza.
This work was supported by CAPES (Fundação Coordenação de Aperfeiçoamento de
Pessoal de Nível Superior), Brazil and by the Swiss National Foundation for Scientific
Research.
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Abstract
The simulation of the human being has been an important research goal in
Computer Graphics. Three main application classes justify this interest: the production of
films for entertainment; the simulation of situations where human beings are involved;
and the development of virtual environments with the embedding of real-time
representation of human participants.
The first goal of our work is the improvement of the realism of human motion.
Considering the complexity of the human body, we can say that the realism of motion
needs to be improved not only from the joint point-of-view, but also in relation to the
body deformation. We propose a method to simulate human beings based on anatomy
concepts, because we believe that the closer our model is from reality, the better will be
our results. Using this approach we have developed our human representation method,
divided into three layers: the rigid body conception from a real skeleton, the muscle
design and deformation based on physics concepts, and the skin generation.
Our skeleton model was designed in two levels. The first one consists in a
topological tree structure with generic information about the joints, their degree of
freedoms, their position, the limit angles of each articulation and so on. The second level
is the bones, that are attached to the joints for animation purposes. The global positions of
the joints are defined based on the reconstructed three-dimensional skeleton while the
limits of the joint angles are fixed from the observation of this skeleton animation.
The muscle representation was also assembled in two levels. In the same way as
the skeleton, we have developed a structure to represent the muscle actions and
attachment to the bones and another one to simulate the muscle shape. We present a
physically-based model to simulate fusiform muscles represented only by their external
surfaces. The deformation is performed with the data coming from the muscle action
structure and with the aid of a mass-spring model applied on the muscle surface.
The Body Builder Plus system is proposed to integrate the skeleton and the
muscles. Our goal in developing this system is to allow the construction of anatomically-
based humans, made exclusively of bones and reconstructed muscles. The combination of
bones and muscles with implicit surface primitives is also proposed in the system. A B-
spline surface is used to simulate the skin covering all the body.
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Résumé
La simulation de l’être humain est un important sujet de recherche en Infographie.
Trois principales catégories d’applications justifient cet intérêt: la production de film
d’animation, la simulation de situations impliquant la présence d’êtres humains, et le
développement d’environnements virtuels comportant la représentation des participants
en temps réel.
Le principal objectif de notre travail a été l’amélioration du réalisme du
mouvement humain. Etant donné la complexité du corps humain, on peut dire que le
réalisme du mouvement a besoin d’être amélioré non seulement du point de vue des
articulations mais aussi sur le plan de la déformation du corps. Nous proposons une
méthode basée sur des concepts anatomiques pour simuler les êtres humains en partant
du principe que, plus le modèle est proche de la réalité, meilleurs seront les résultats
obtenus. En utilisant cette approche nous avons développé notre méthode de
représentation humaine, divisée en trois couches : la conception de la partie rigide du
corps à partir d’un squelette réel, la conception et la déformation des muscles basées sur
des concepts physiques, et la génération de la peau.
Notre modèle de squelette a été conçu en deux parties. La première consiste en
une structure arborescente topologique avec des informations génériques concernant les
articulations, leurs degrés de liberté, positions , limites angulaires, etc. Le second niveau
est composé des os qui sont attachés aux articulations à des fins d’animation. Un
squelette tri-dimentionel en image de synthèse a permis de définir les positions globales
des articulations. Les limites des articulations ont été fixées à partir d’observations du
squelette en mouvement.
La représentation des muscles a également été définie en deux niveaux. De même
que pour le squelette, nous avons développé deux structures, une pour représenter les
actions des muscles et leurs attachements aux os et l’autre pour simuler la forme du
muscle. Nous présentons un modèle basé sur la physique pour simuler les muscles
fusiformes modélisés simplement par leur surface externe. La déformation est produite à
partir des données provenant des actions des muscles et d’un modèle masse-ressort
appliqué sur la surface du muscle.
L’application Body Builder Plus est proposée afin d’intégrer le squelette et les
muscles. Notre objectif en développant ce système est de permettre, soit la construction
de corps humains basés sur l’anatomie à partir exclusivement d’os et de muscles, soit la
combinaison des os et des muscles avec des primitives de surface implicite. Une surface
B-spline simule la peau sur tout le corps.
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Contents
ACKNOWLEDGMENTS.................................................................................................3
ABSTRACT.......................................................................................................................4
RÉSUMÉ............................................................................................................................5
CONTENTS.......................................................................................................................7
1. INTRODUCTION.......................................................................................................11
1.1. Motivation.............................................................................................................11
1.1.1. Importance and Relevance...............................................................................11
1.1.2. Problematics.....................................................................................................12
1.1.3. Applications.....................................................................................................12
1.2. Aims and Objectives.............................................................................................13
1.3. Organization.........................................................................................................15
2. REVIEW.......................................................................................................................17
2.1. Introduction..........................................................................................................17
2.2. Human Body Modeling and Animation.............................................................17
2.2.1. Evolution of Human Animation......................................................................17
2.2.2. Stick Figure Model..........................................................................................18
2.2.3. Surface Models................................................................................................18
2.2.4. Volume Models................................................................................................19
2.2.5. Multi-layered Models.......................................................................................20
2.3. Deformable Models..............................................................................................24
2.3.1. Geometric Deformation Methods....................................................................24
2.3.2. Physically-Based Methods...............................................................................29
2.3.3. Hybrid Methods...............................................................................................35
2.4. Conclusion.............................................................................................................37
3. ANATOMICALLY-BASED SKELETON DESIGN..............................................39
3.1. Introduction..........................................................................................................39
3.2. BODY Structure Description................................................................................39
3.3. Anatomic Template..............................................................................................41
3.4. Review of the BODY Degrees of Freedom (DOF).............................................43
3.4.1. DOFs of the Lower Body.................................................................................44
3.4.2. DOFs of the Upper Body: The Spine...............................................................46
3.4.3. DOFs of the Upper Body: Thorax and Arms...................................................49
3.4.4. Local Frame of the Hands................................................................................51
3.4.5. Local Frame of the Head..................................................................................51
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3.5. Why Representing Bones?...................................................................................52
3.6. Conclusion.............................................................................................................53
4. MUSCLE MODEL......................................................................................................55
4.1. Introduction..........................................................................................................55
4.2. Muscles Physiology and Anatomy......................................................................55
4.2.1. Structural Description......................................................................................56
4.2.2. Activation and Contraction..............................................................................56
4.2.3. Types of Contraction........................................................................................58
4.2.4. Skeletal Muscle Architecture...........................................................................59
4.2.5. Tendons and Ligaments...................................................................................59
4.3. Action Lines..........................................................................................................60
4.3.1. Muscle Force Modeling...................................................................................60
4.3.2. Our Approach...................................................................................................61
4.4. Muscle Shape Design............................................................................................63
4.4.1. Reconstructed Muscles....................................................................................63
4.4.2. From Ellipsoids to Muscles.............................................................................66
4.4.3. Manual Shape Input.........................................................................................67
4.4.4. Resampling Method.........................................................................................67
4.5. Deformation Model..............................................................................................69
4.5.1. Elasticity..........................................................................................................70
4.5.2. Curvature and Torsion.....................................................................................71
4.5.3. Geometric Constraints.....................................................................................73
4.6. Motion Simulation................................................................................................74
4.6.1. Numerical Integration Through Time..............................................................74
4.6.2. Our Implementation.........................................................................................75
4.7. Some Details about the Implementation............................................................77
4.7.1. How to Build a Deformable Muscle?..............................................................77
4.7.2. The Parameters.................................................................................................79
4.7.3. The Data Structure............................................................................................79
4.8. Animation Examples............................................................................................80
4.9. Conclusion.............................................................................................................83
5. BODY BUILDER PLUS, THE INTEGRATION TOOL........................................85
5.1. Introduction..........................................................................................................85
5.2. Overview...............................................................................................................85
5.2.1. Volume Primitives...........................................................................................86
5.2.2. The Extremities................................................................................................86
5.2.3. The Skin...........................................................................................................86
5.3. System Organization............................................................................................89
5.3.1. Architecture......................................................................................................89
5.3.2. Data Structure..................................................................................................90
5.3.3. The Motion Motor Algorithm..........................................................................91
5.4. How to Build an Anatomically-Based Body?.....................................................94
5.4.1. Skeleton Definition..........................................................................................94
5.4.2. Adding Bones..................................................................................................94
5.4.3. Creating Muscles.............................................................................................95
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5.4.4. Skin Generation...............................................................................................96
5.5. Results and Discussion.........................................................................................97
5.6. Conclusion.............................................................................................................99
6. CONCLUSIONS........................................................................................................101
6.1. Introduction........................................................................................................101
6.2. Contribution.......................................................................................................101
6.3. Potential Applications........................................................................................102
6.4. Future Work.......................................................................................................104
APPENDIX A: TEMPLATE DEFINITION FILES.................................................107
A.1. Template File (newton.tpl)................................................................................107
A.2. Joint Limits File (newton.jts)...........................................................................110
BIBLIOGRAPHY..........................................................................................................113
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