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Medicine is a discipline where visualization is an essential component of learning. However, the three-dimensional, dynamic structure of the human body poses difficult teaching challenges. There is a need for truly interactive computer tools that will enable students to create and manipulate computer models, not just watch them. We propose dierent approaches with that goal in mind. We were first interested in interactive physically-based animation of anisotropic elastic materials. One possible application scenario is an anatomy course on heart physiology where students can build interactive samples of cardiac muscular tissue. To achieve this, our model exhibits two key features. The first one is a low computational cost that results in high frame rates; the second one is an intuitive system image that ensures easy control by the user. Next, we were interested in interaction in three dimensions using two-dimensional input, either for annotating existing models, or for creating new models; taking advantage of the fact that drawing practice is still considered a fundamental learning method by some anatomy teachers in the French medical school curriculum. Our 3D drawing system has a stroke representation that enables drawing redisplay when the viewpoint changes. Moreover, this representation can be mixed freely with existing polygonal surfaces for annotation purposes. In contrast, our modeling by drawing tool uses information from both stroke geometry and the drawn image, to allow three-dimensional modeling without explicit depth specification.
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iMAGIS-GRAVIR / IMAG
Animation interactive et modélisation par le dessin
Applications pédagogiques en médecine
David Bourguignon
Doctorat de l’INPGSpécialité : modèles et instruments en médecine et biologie
Préparé au sein du laboratoire GRAVIRSous la direction de Marie-Paule Cani
M.C. Escher
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Burgeoning field
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Burgeoning field
•Biology and medicine are visual disciplines– Three-dimensional shapes
Frog tomography data
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Burgeoning field
•Biology and medicine are visual disciplines– Three-dimensional shapes– Dynamic phenomena
Dynamic imagingleft ventricle human heart
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Burgeoning field
•Biology and medicine are visual disciplines– Three-dimensional shapes– Dynamic phenomena
•Problems for teaching using real organisms– Practical availability
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Burgeoning field
•Biology and medicine are visual disciplines– Three-dimensional shapes– Dynamic phenomena
•Problems for teaching using real organisms– Practical availability– Practical feasibility
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)
http://www.netanatomy.com
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)– Multimedia documents
http://www.froguts.com
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)– Multimedia documents
http://www.froguts.com
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)– Multimedia documents
http://www.froguts.com
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)– Multimedia documents
•Drawbacks– No editing tools available
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Current solutions– Anatomical databases (images, 3D models)– Multimedia documents
•Drawbacks– No editing tools available– Teacher and students in observer role
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools– User-centered
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools– User-centered– Understand shape and function of organs
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools– User-centered– Understand shape and function of organs– Create, edit, animate models
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools
•Two interdisciplinary collaborations– MENRT research action “Beating heart”
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools
•Two interdisciplinary collaborations– MENRT research action “Beating heart”– Anatomy laboratory CHU Grenoble
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools
•Two interdisciplinary collaborations
•Two pedagogical scenarios– Physiological anatomy course
• Build interactive samples
• Experiment
iMAGIS-GRAVIR / IMAG
Information Technology in Teaching
•Need for truly interactive teaching tools
•Two interdisciplinary collaborations
•Two pedagogical scenarios– Physiological anatomy course– Structural anatomy course
• Draw or annotate
• Create or edit
iMAGIS-GRAVIR / IMAG
Our Contributions
•Part 1: Interactive physically based animation– Animating anisotropic elastic materials
[Bourguignon and Cani, EGCAS 2000]
•Part 2: Interaction in 3D using 2D input– Drawing in 3D [Bourguignon et al., EG 2001]– Modeling by drawing
iMAGIS-GRAVIR / IMAG
Our Contributions
•Part 1: Interactive physically based animation– Animating anisotropic elastic materials
[Bourguignon and Cani, EGCAS 2000]
•Part 2: Interaction in 3D using 2D input– Drawing in 3D [Bourguignon et al., EG 2001]– Modeling by drawing
iMAGIS-GRAVIR / IMAG
Motivation
•Manipulate interactive samples
Part 1
iMAGIS-GRAVIR / IMAG
Motivation
•Manipulate interactive samples
•Biological materials– Dynamics– Nonlinear elasticity– Anisotropy– Incompressibility
Part 1
Computer model ofcardiac geometry andmuscle fiber (McCulloch, UCSD)
iMAGIS-GRAVIR / IMAG
Motivation
•Manipulate interactive samples
•Biological materials– Dynamics– Nonlinear elasticity– Anisotropy– Incompressibility
Human liver (Epidaure, INRIA)
Part 1
iMAGIS-GRAVIR / IMAG
Motivation
•Manipulate interactive samples
•Biological materials
• Intuitively and efficiently
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Continuous Models– Large deformations [O’Brien and Hodgins, 1999]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Continuous Models– Large deformations [O’Brien and Hodgins, 1999]– Multiresolution [Debunne et al., 2001]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Continuous Models– Large deformations [O’Brien and Hodgins, 1999]– Multiresolution [Debunne et al., 2001]– Physical nonlinearities and transversal isotropy
[Picinbono et al., 2001]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Continuous Models– Large deformations [O’Brien and Hodgins, 1999]– Multiresolution [Debunne et al., 2001]– Physical nonlinearities and transversal isotropy
[Picinbono et al., 2001]
•Problems– Incompressibility
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Continuous Models– Large deformations [O’Brien and Hodgins, 1999]– Multiresolution [Debunne et al., 2001]– Physical nonlinearities and transversal isotropy
[Picinbono et al., 2001]
•Problems– Incompressibility– Parameters setting
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Discrete Models– Large deformations
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Discrete Models– Large deformations– Physical nonlinearities [Lee et al., 1995]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Discrete Models– Large deformations– Physical nonlinearities [Lee et al., 1995]
•Problems– No multiresolution [Debunne et al., 2001]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Discrete Models– Large deformations– Physical nonlinearities [Lee et al., 1995]
•Problems– No multiresolution [Debunne et al., 2001]– Anisotropy [Ng and Fiume, 1997]
Part 1
iMAGIS-GRAVIR / IMAG
Previous Work
•Discrete Models– Large deformations– Physical nonlinearities [Lee et al., 1995]
•Problems– No multiresolution [Debunne et al., 2001]– Anisotropy [Ng and Fiume, 1997]– Incompressibility
Part 1
iMAGIS-GRAVIR / IMAG
Mass-Spring Systems
• Mesh geometry influences material behavior– Undesired anisotropy
– Incorrect behavior in bending
Tetrahedral mass-spring system
Part 1
iMAGIS-GRAVIR / IMAG
Mass-Spring Systems
• Mesh geometry influences material behavior– Undesired anisotropy
– Incorrect behavior in bending
Part 1
Tetrahedral mass-spring system
iMAGIS-GRAVIR / IMAG
Our Approach
•Goal– As simple and efficient as mass-spring system– Speed vs precision tradeoff– Anisotropy– Incompressibility
Part 1
iMAGIS-GRAVIR / IMAG
Our Approach
•Goal– As simple and efficient as mass-spring system– Speed vs precision tradeoff– Anisotropy– Incompressibility
•Choice– Discrete model– Uncouple forces directions and mesh geometry
[Barzel, 1992]
Part 1
iMAGIS-GRAVIR / IMAG
Our Approach
•Data: Geometry
Surface mesh
Part 1
iMAGIS-GRAVIR / IMAG
Our Approach
•Data: Geometry
Surface mesh
Part 1
Volume mesh
iMAGIS-GRAVIR / IMAG
Our Approach
•Data: Vector field
Surface mesh
Part 1
Volume mesh
Vector field
iMAGIS-GRAVIR / IMAG
Our Approach
•Elements
Surface mesh
Part 1
Volume mesh
Vector field
Barycenter
Axes of interest(mechanical characteristics)
iMAGIS-GRAVIR / IMAG
Our Approach
•Elements
Surface mesh
Part 1
Volume mesh
Vector field
Barycenter
Axes of interest(mechanical characteristics)
For each element:1. Element deformation2. Local frame deformation3. Forces applied to local frame4. Forces applied to nodes
iMAGIS-GRAVIR / IMAG
Forces Calculations
Stretch:Axial damped spring forces (each axis)
Shear:Angular spring forces(each pair of axes)
f1
I1’
I1
e1
f1’
f3
I1’
I1 e1
e3
I3
I3’f1
f1’
f3’
Part 1
iMAGIS-GRAVIR / IMAG
Volume Conservation• Soft constraint [Lee et al., 1995]
• Conserve sum of barycenter-vertices distances
fC
fB
fD
fA
Part 1
iMAGIS-GRAVIR / IMAG
Volume Conservation
•Comparison with mass-spring systems
With volume conservationforces
Mass-spring system
Without volume conservationforces
Part 1
iMAGIS-GRAVIR / IMAG
Results• Comparison with mass-spring systems
– No more undesired anisotropy
– Correct behavior in bending
Orthotropic material (as muscle fiber)Same parameters in the 3 directions
Part 1
iMAGIS-GRAVIR / IMAG
Results• Comparison with mass-spring systems
– No more undesired anisotropy
– Correct behavior in bending
Part 1
Orthotropic material (as muscle fiber)Same parameters in the 3 directions
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Horizontal
Part 1
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Diagonal
Part 1
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Part 1
Hemicircular
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Part 1
Concentric Helicoidal
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Part 1
Concentric Helicoidal (top view)
iMAGIS-GRAVIR / IMAG
Results• Different anisotropic behaviors with same tetrahedral mesh
Part 1
Random
iMAGIS-GRAVIR / IMAG
Validations
• Emerging behavior [Boux de Casson, 2000]– Define a behavior at the element level
– Measure the emerging behavior at the object level
Part 1
iMAGIS-GRAVIR / IMAG
Validations
• Emerging behaviorObject level behavior
Part 1
f1
I1’
I1
e1
f1’
Element level behavior (data points fit) +
iMAGIS-GRAVIR / IMAG
Validations
• Multiresolution behavior [Debunne, 2000]
Part 1
iMAGIS-GRAVIR / IMAG
Validations
• Multiresolution behavior [Debunne, 2000]
Mass-spring system Our model
Part 1
iMAGIS-GRAVIR / IMAG
Conclusion and Future Work
•Conclusion: Pedagogical application– Build interactive samples of biological materials
• Nonlinear, anisotropic behaviors
• Soft constraint for volume conservation
• Efficient
Part 1
iMAGIS-GRAVIR / IMAG
Conclusion and Future Work
•Conclusion: Pedagogical application– Build interactive samples of biological materials
• Nonlinear, anisotropic behaviors
• Soft constraint for volume conservation
• Efficient
– Experiment by varying model parameters• Intuitive system image [Norman, 1988]
Part 1
iMAGIS-GRAVIR / IMAG
Conclusion and Future Work
•Conclusion: Pedagogical application
•Future work: “Animated sketches”– Draw sample
Part 1
iMAGIS-GRAVIR / IMAG
Conclusion and Future Work
•Conclusion: Pedagogical application
•Future work: “Animated sketches”– Draw sample– Specify parameters by drawing
Part 1
iMAGIS-GRAVIR / IMAG
Conclusion and Future Work
•Conclusion: Pedagogical application
•Future work: “Animated sketches”– Draw sample– Specify parameters by drawing
Animate!
Part 1
iMAGIS-GRAVIR / IMAG
Our Contributions
•Part 1: Interactive physically based animation– Animating anisotropic elastic materials
[Bourguignon and Cani, EGCAS 2000]
•Part 2: Interaction in 3D using 2D input– Drawing in 3D [Bourguignon et al., EG 2001]– Modeling by drawing
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw– Writing alternative
• Faster
• More convenient
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw– Writing alternative– Minimal tool set
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw– Writing alternative– Minimal tool set– Since kindergarten
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw
•Few people sculpt– Materials difficult to handle
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw
•Few people sculpt– Materials difficult to handle– Simpler with computer ?
• Scanning
• Modeling
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Most people draw
•Few people sculpt
•Drawing application: Teaching– Example: Pr. Jean-Paul Chirossel, anatomy
laboratory CHU Grenoble
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Drawing characteristics– Visual abstraction
Human heart
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Drawing characteristics– Visual abstraction– Indication of uncertainty
Leonardo da Vinci
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Drawing characteristics– Visual abstraction– Indication of uncertainty– Limitation to single viewpoint
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Drawing characteristics– Visual abstraction– Indication of uncertainty– Limitation to single viewpoint
•Problems– Drawing with multiple viewpoints
Part 2
iMAGIS-GRAVIR / IMAG
Motivation
•Drawing characteristics– Visual abstraction– Indication of uncertainty– Limitation to single viewpoint
•Problems– Drawing with multiple viewpoints– Modeling by drawing
Part 2
iMAGIS-GRAVIR / IMAG
Our Contributions
•Part 1: Interactive physically based animation– Animating anisotropic elastic materials
[Bourguignon and Cani, EGCAS 2000]
•Part 2: Interaction in 3D using 2D input– Drawing in 3D [Bourguignon et al., EG 2001]– Modeling by drawing
Part 2.1
iMAGIS-GRAVIR / IMAG
Previous Work
•2D-to-3D drawing: 3D Strokes– Input stroke and its shadow [Cohen et al., 1999]
• 3D curves design, no drawing
Part 2.1
iMAGIS-GRAVIR / IMAG
Previous Work
•2D-to-3D drawing: 3D Strokes– Input stroke and its shadow [Cohen et al., 1999]– Deep canvas [Disney, 1999]
• Need a 3D model
Part 2.1
iMAGIS-GRAVIR / IMAG
Previous Work
•2D-to-3D drawing: 3D Strokes– Input stroke and its shadow [Cohen et al., 1999]– Deep canvas [Disney, 1999]– Billboard, terrain, etc., stroke [Cohen et al., 2000]
• Drawing modes adapted to landscaping only
Part 2.1
iMAGIS-GRAVIR / IMAG
Previous Work
•2D-to-3D drawing: 3D Strokes
•2D-to-3D drawing: 3D Objects– Reconstruction [Lipson and Shpitalni, 1996]
• No free-form drawing
Part 2.1
iMAGIS-GRAVIR / IMAG
Previous Work
•2D-to-3D drawing: 3D Strokes
•2D-to-3D drawing: 3D Objects– Reconstruction [Lipson and Shpitalni, 1996]– Sketching interface [Igarashi et al., 1999]
• Closed strokes only
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D– Augment strokes to true 3D entities
• Line stroke: Space curve (view-independent)
Eye
Edgar Degas
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D– Augment strokes to true 3D entities
• Line stroke: Space curve (view-independent)
• Silhouette stroke: Surface contour (view-dependent)
Back
Edgar Degas
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D– Augment strokes to true 3D entities– Annotation of existing 3D models
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D– Augment strokes to true 3D entities– Annotation of existing 3D models– Illustration in 3D
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D
•Choices– Represent line stroke as space curve
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Approach
•Drawing in 3D
•Choices– Represent line stroke as space curve– Represent silhouette stroke using local surface
• Infer local surface from user input
• New silhouette from new viewpoint
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
• Infer local surface from user input– Simplest: same local curvature in 3D as in 2D
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
• Infer local surface from user input– Simplest: same local curvature in 3D as in 2D– Modulate width as if fitting circles along curve
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
• Infer local surface from user input– Simplest: same local curvature in 3D as in 2D– Modulate width as if fitting circles along curve– Resulting surface
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
•New silhouette from new viewpoint– Approximate silhouette
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
•New silhouette from new viewpoint– Approximate silhouette– Represent uncertainty away from viewpoint
Part 2.1
iMAGIS-GRAVIR / IMAG
Silhouette Stroke
•New silhouette from new viewpoint– Approximate silhouette– Represent uncertainty away from viewpoint– Manage occlusion with background color
Part 2.1
iMAGIS-GRAVIR / IMAG
Interface for Drawing
•Two drawing modes– In empty space
Part 2.1
iMAGIS-GRAVIR / IMAG
Interface for Drawing
•Two drawing modes– In empty space– Relatively to other objects
Part 2.1
iMAGIS-GRAVIR / IMAG
Interface for Drawing
•Video
Part 2.1
iMAGIS-GRAVIR / IMAG
Applications
•Annotation
Part 2.1
iMAGIS-GRAVIR / IMAG
Applications
• Illustration
Part 2.1
iMAGIS-GRAVIR / IMAG
Conclusion
•System for drawing in 3D– View-dependent strokes
Part 2.1
iMAGIS-GRAVIR / IMAG
Conclusion
•System for drawing in 3D– View-dependent strokes– Useful for drawing simple scenes in 3D
Part 2.1
iMAGIS-GRAVIR / IMAG
Conclusion
•System for drawing in 3D– View-dependent strokes– Useful for drawing simple scenes in 3D– Useful for annotations
Part 2.1
iMAGIS-GRAVIR / IMAG
Conclusion
•System for drawing in 3D
•Limitations– Switching between stroke types
Part 2.1
iMAGIS-GRAVIR / IMAG
Conclusion
•System for drawing in 3D
•Limitations– Switching between stroke types– Plane positioning can be tedious
Part 2.1
iMAGIS-GRAVIR / IMAG
Our Contributions
•Part 1: Interactive physically based animation– Animating anisotropic elastic materials
[Bourguignon and Cani, EGCAS 2000]
•Part 2: Interaction in 3D using 2D input– Drawing in 3D [Bourguignon et al., EG 2001]– Modeling by drawing
Part 2.2
iMAGIS-GRAVIR / IMAG
Motivation
• Input: Just plain strokes…– Silhouette, sharp features ?– Texture, shading ?– Open, closed, self-intersecting ?
Part 2.2
iMAGIS-GRAVIR / IMAG
Motivation
• Input: Just plain strokes…
•Output: Manifold polyhedral surface
Part 2.2
iMAGIS-GRAVIR / IMAG
Motivation
• Input: Just plain strokes…
•Output: Manifold polyhedral surface
•Pen-and-paper for sculptors– Painter and sculptor shading
Michelangelo BuonarrotiRembrandt van Rijn
Part 2.2
iMAGIS-GRAVIR / IMAG
Previous Work•Painting depth as luminance [Williams, 1990]
Part 2.2
+
iMAGIS-GRAVIR / IMAG
Previous Work•Silhouette inflation [Williams, 1991]
Part 2.2
iMAGIS-GRAVIR / IMAG
Previous Work•Editing gradient by shading [van Overveld, 1996]
Part 2.2
iMAGIS-GRAVIR / IMAG
Previous Work•Bump map inference [Johnston, 2002]
Part 2.2
iMAGIS-GRAVIR / IMAG
Previous Work•Direct manipulation interface
Artisan [Alias|wavefront, 2002]
ZBrush [Pixologic, 2002]
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes2Ddiscontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes
Geometry
2Ddiscontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes
Geometry Constrained triangulation
2Ddiscontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes
Geometry Constrained triangulation
Non-convex hull
2Ddiscontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes
Geometry
Image
Constrained triangulation
Non-convex hull
2Ddiscontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Overview
Strokes
Geometry
Image
Constrained triangulation
Non-convex hull
Height field
2Ddiscontinuous
2.5Dcontinuous
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D•Find a non-convex hull
– Original drawing (polylines)
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D•Find a non-convex hull
– Original drawing (polylines)– Constrained Delaunay triangulation
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D•Find a non-convex hull
– Original drawing (polylines)– Constrained Delaunay triangulation– Non-convex hull [Watson, 1997]
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D•Hole marks
– In comics books production
Stone #3, Avalon Studios
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D•Hole marks
– In comics books production– In our system
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field
– Large features have large inflations
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field
– Large features have large inflations– Use geometry information to build it
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field
– Large features have large inflations– Use geometry information to build it– Use texture information to modulate it
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: First step
– Euclidean distance transform
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: First step
– Mapping to unit sphere [Oh et al., 2001]
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: First step
– Adaptive low pass filter [Williams, 1991]
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: Second step
– Use same filter for image
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: Third step
– Use previous height field as matte for image
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D• Infer a height field: Result
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Fast polygonal height field approximation [Garland and Heckbert, 1995]
Part 2.2
iMAGIS-GRAVIR / IMAG
From 2D to 2.5D
•Result: Manifold polyhedral surface
Part 2.2
iMAGIS-GRAVIR / IMAG
Results
•A simple sketch of a human heart
iMAGIS-GRAVIR / IMAG
Conclusion
•System for modeling by drawing– Plain strokes as input– Manifold polyhedral surface as output– Using sculptor shading convention
Part 2.2
iMAGIS-GRAVIR / IMAG
Conclusion
•System for modeling by drawing– Plain strokes as input– Manifold polyhedral surface as output– Using sculptor shading convention
•Limited to a single viewpoint
Part 2.2
iMAGIS-GRAVIR / IMAG
Future Work
•From 2.5D to 3D: Iterative modeling process
Modeling by drawing
Changing viewpoint
Part 2.2
iMAGIS-GRAVIR / IMAG
Future Work
•Relief metaphor– From low to high relief– From painting to sculpture
Fourth century B.C.
First century B.C.
Fifteenth century
Part 2.2
iMAGIS-GRAVIR / IMAG
General Conclusion
•Animation of anisotropic material– Intuitive– Efficient
iMAGIS-GRAVIR / IMAG
General Conclusion
•Animation of anisotropic material
•Three-dimensional drawing system– Use drawing characteristics– Good geometric detail vs modeling speed tradeoff
iMAGIS-GRAVIR / IMAG
General Conclusion
•Animation of anisotropic material
•Three-dimensional drawing system
•Modeling by drawing from a single viewpoint
iMAGIS-GRAVIR / IMAG
General Future Work
•Evaluation according to ergonomics methods
•“Drawing as a front-end to everything” [Gross and Do, 1996]
iMAGIS-GRAVIR / IMAG
Merci de votre attention
iMAGIS-GRAVIR / IMAG