Transcript Painting folds using expansion textures

Painting folds using
expansion textures
Jean Combaz
Fabrice Neyret
iMAGIS is a joint project of CNRS - INPG - INRIA - UJF
http://www-imagis.imag.fr/Membres/Jean.Combaz/
iMAGIS-GRAVIR / IMAG
Motivations
More realistic images
More details
More complexity
• Drape and folds
– Cloth material
– Elastic surface + constraints
folds
iMAGIS-GRAVIR / IMAG
Motivations
• 2 solutions:
– Physical simulation
– Shape modeling
• But:
– We just want a plausible shape, not a physical one
– Physical parameters, initial conditions ?
– Fastidious task in a geometric modeler
iMAGIS-GRAVIR / IMAG
Motivations
• Goal:
– Add details on a surface
– High level of control
– Close to sculpture
iMAGIS-GRAVIR / IMAG
Plan
• Motivations
• Previous work
– Specifying the detailled shapes
– Representing the detailled shapes
• Expansion textures
– From the user’s point of view
– From the programmer’s point of view
• Results
• Conclusion
iMAGIS-GRAVIR / IMAG
Previous work: specifying the
detailled shapes
• Interactive tools
user
Details
editor
details
Modeler
Direct painting
[Hanrahan90]
FFD
[Sederberg86]
[Coquillart90]
Alias wavefrontMaya Artisan™
iMAGIS-GRAVIR / IMAG
Previous work: specifying the
detailled shapes
• Procedural tools
user
Details
generator
Generic generators
[Perlin85]
([Ebert94], [Fournier80], [Perlin89])
details
Specialized generators
[Fleischer95]
[Prusinkiewicz93]
([Badler90], [Wong97])
iMAGIS-GRAVIR / IMAG
Previous work: specifying the
detailled shapes
• Simulation tools
Physical
solver
user
Cloth material
[Breen94]
[Baraff98]
[Terzopoulos88]
details
Biological patterns
[Fowler92]
[Turk91]
[Witkin91]
iMAGIS-GRAVIR / IMAG
Plan
• Motivations
• Previous work
– Specifying the detailled shapes
– Representing the detailled shapes
• Expansion textures
– From the user’s point of view
– From the programmer’s point of view
• Results
• Conclusion
iMAGIS-GRAVIR / IMAG
Previous work: representing the
detailled shapes
• 3D surface encoding
Polygonal meshes
Voxels
Surfels
• Displacement mapping
[Guskov99]
([Wang00])
• Bump maps
([Blinn78])
iMAGIS-GRAVIR / IMAG
Previous work: representing the
detailled shapes
• Texels, hypertextures
[Kajiya89]
[Neyret98]
[Perlin89]
• Transitions
[Cohen98]
([Becker93], [Max86])
iMAGIS-GRAVIR / IMAG
Plan
• Motivations
• Previous work
– Specifying the detailled shapes
– Representing the detailled shapes
• Expansion textures
– From the user’s point of view
– From the programmer’s point of view
• Results
• Conclusion
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
Offline painting
• Expansion texture
Interactive painting
Procedural generation
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
– Location
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
– Location
– Orientation
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
– Location
– Orientation
– Magnitude of expansion
x 1.5
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
–
–
–
–
Location
Orientation
Magnitude of expansion
Style information
• Desired wavelength
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
–
–
–
–
Location
Orientation
Magnitude of expansion
Style information
• Desired wavelength
• Regularity
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
• Geometry: Triangular mesh
• Expansion texture
–
–
–
–
Location
Orientation
Magnitude of expansion
Style information
• Desired wavelength
• Regularity
– Constraints, attachments
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
user’s point of view
Example: Interactive painting of folds
iMAGIS-GRAVIR / IMAG
Plan
• Motivations
• Previous work
– Specifying the detailled shapes
– Representing the detailled shapes
• Expansion textures
– From the user’s point of view
– From the programmer’s point of view
• Results
• Conclusion
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
– Reference state
• Triangular mesh
• Rest length l0
• Rest curvature 0
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
– Reference state
• Triangular mesh
• l 0 , 0
– Expansion (or contraction)
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
– Reference state
• Triangular mesh
• l 0 , 0
– Expansion (or contraction)
→Update rest lengths
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
– Reference state
• Triangular mesh
• l 0 , 0
– Expansion (or contraction)
→Update rest lengths
– Mesh optimization
• According to the new rest lengths
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Algorithm
– Reference state
• Triangular mesh
• l 0 , 0
– Expansion (or contraction)
→Update rest lengths
– Mesh optimization
– Solver
→Displacements to decrease the stress
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
• Texture Expansion
• Physical model
• Solver
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Texture Expansion
An expansion tensor field
2x2 symetric matrix τ
2D vector u
Isotropic
expansion
Expansion
Anisotropic
unidirectional
expansion
new length
ut τ u
Anisotropic
expansion
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
Pysical model
3 kinds of forces:
Tangential response FT
FT = FE - (FE . N) N
FE is a elastic force (Green-Lagrange F.E.)
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
• Displacements
dP = .F
= .(FT + FN + F)
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
• Displacements
dP = .F
= .(FT + FN + F)
N
FT: tangential response
FT = FE - (FE . N) N
FE is a elastic force
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
• Displacements
dP = .F
= .(FT + FN + F)
N
FT: tangential response
FN: normal response
FN = (kp f(-0) + kpi) Ca N
to create folds
iMAGIS-GRAVIR / IMAG
Expansion textures:
programmer’s point of view
• Displacements
dP = .F
= .(FT+FN+F)
NN
FT: tangential response
FN: normal response
F: curvature control
F = - k (-0) N
to smooth folds
iMAGIS-GRAVIR / IMAG
Plan
• Motivations
• Previous work
– Specifying the detailled shapes
– Representing the detailled shapes
• Expansion textures
– From the user’s point of view
– From the programmer’s point of view
• Results
• Conclusion
iMAGIS-GRAVIR / IMAG
Results: Regular folds
Initial shape: square
Expansion rate: 1.5 (anisotropic)
Constraint:
left and right border attached
Real plastic cover
iMAGIS-GRAVIR / IMAG
Results: Non uniform expansion
Initial shape: square
Expansion rate: 1.0 1.5 (anisotropic)
Constraint:
all borders are attached
iMAGIS-GRAVIR / IMAG
Results: Coat folded in a ring area
Initial shape: square
Expansion rate: 1.5 (anisotropic)
Constraint:
all borders are attached
iMAGIS-GRAVIR / IMAG
Results: scrunchy
Initial shape: torus
Expansion rate: 2.5 (anisotropic)
Constraint:
a small torus inside the shape
iMAGIS-GRAVIR / IMAG
Results: scrunchy
Initial shape: torus
Expansion rate: 2.5 (anisotropic)
Constraint:
a small torus inside the shape
iMAGIS-GRAVIR / IMAG
Results: circumvolution shapes
isotropic expansion
iMAGIS-GRAVIR / IMAG
Results: circumvolution shapes
isotropic expansion
iMAGIS-GRAVIR / IMAG
Conclusion
• Expansion textures: a new paradigm
• High level of control
• Add thin details
• Close to a physical simulation solver
• Close to sculpture and painting from the user
point of view
iMAGIS-GRAVIR / IMAG
Future work
• To be improved
– Solver (computation time)
– Folds shape control
• Bump mapping
• Morphogenesis (huge expansion)
– Self-intersections
– Generation of procedural expansion textures
iMAGIS-GRAVIR / IMAG
Questions ?
iMAGIS-GRAVIR / IMAG