A Painting Interface for Interactive Surface Deformations

1
A Painting Interface for Interactive Surface
Deformations

• Jason Lawrence
• Thomas Funkhouser
• Princeton University

2
Motivation

• Many objects are hard to model

3
Challenges

• Complex Surfaces
• Scale
• User Control

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Challenges

• Complex Surfaces
• Scale
• User Control

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Challenges

• Complex Surfaces
• Scale
• User Control

Museth et al.
6
Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

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Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

8
Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

9
Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

10
Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

11
Existing Interfaces

• Control lattice
• Free-form deformations
• NURBS surface control points
• Physical Simulation
• Deformable Models
• Level Set Editing Operators
• Sculpting interfaces
• Voxel-based sculpting
• Surface sculpting

Maya Artisan Sculpt Surface Tool
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Key Observation

• Directly painting and then interactively
  simulating is a more controllable, powerful way
  to locally deform surfaces.

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Our Approach

• The user paints directly onto the surface of an
  object.
• Paint is interpreted as the instantaneous surface
  velocity.
• User simulates velocity until the desired effect
  is achieved.

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Our Approach

• The user paints directly onto the surface of an
  object.
• Paint is interpreted as the instantaneous surface
  velocity.
• User simulates velocity until the desired effect
  is achieved.

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Our Approach

• The user paints directly onto the surface of an
  object.
• Paint is interpreted as the instantaneous surface
  velocity.
• User simulates velocity until the desired effect
  is achieved.

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Overview of Talk

• Introduction
• Method
• Applying Paint
• Defining Paint
• Simulating Paint
• Results

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Overview of Talk

• Introduction
• Method
• Applying Paint
• Defining Paint
• Simulating Paint
• Results

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Applying Paint

• Directly inject paint into scene.
• Use 2D brush bitmaps to modulate intensity
  Hanrahan90.

Various Brushes
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Applying Paint
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Applying Paint
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Overview of Talk

• Background
• Method
• Applying Paint
• Defining Paint
• Simulating Paint
• Results

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Defining Paint

• What is paint?
• Paint describes surface velocity

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Surface Velocity

• Surface velocity can capture useful modeling
  operations
• Propagating organic, blobby deformations
• Advective spiky, discontinuous
• Curvature-dependent diffusion

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Surface Velocity

• We define surface velocity at some point along
  the models surface x, with surface normal n, as
  the linear combination of three terms
• v(x) vprop(x) vadv(x) vcurv(x)

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Propagating Velocity

• Propagating velocity causes the surface to move
  in the direction of its current surface normal,
  producing blobby, organic deformations
• vprop(x) an

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Propagating Velocity
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Advective Velocity

• Advective velocity causes the surface to move
  at a constant speed in a constant direction
• vadv(x) ßp

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Advective Velocity
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Curvature-Dependent Velocity

• Curvature-dependent velocity causes the surface
  to move at a speed proportional to its mean
  curvature, ?, in the direction of its surface
  normal.
• vcurv(x) ??n

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Curvature-Dependent Velocity
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Specify Paint

• Total velocity of a point on the models surface
• v(x) an ßp ??n

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Specify Paint

• The paint IS the values of a, ß, and ?.
• The direction of advective motion, p, determined
  by current viewing direction, surface normal, or
  arbitrary direction.

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Overview of Talk

• Background
• Method
• Applying Paint
• Defining Paint
• Simulating Paint
• Results

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Simulating Paint

• Goal move surface according to velocity user has
  painted.

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Dynamic Surface

• We need a surface representation that supports
• Interactive update rates.
• Associate paint with surface.
• Editing at multiple scales.
• Created prototype system with two
  representations
• Level Sets
• Dynamic Triangle Mesh

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Triangle Mesh

• Represent surface as triangle mesh where the
  vertices are free to move in space.
• Store paint at each vertex.

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Adaptive Refinement

• Our implementation provides two types of mesh
  refinement
• Temporal refine mesh during deformation to
  accurately sample the dynamic surface.
• Brush-Dependent refine mesh depending on
  location and orientation of brush to accurately
  sample the brush.

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Temporal Refinement

• Explicitly maintain an even distribution of
  vertices over the surface by refining mesh.

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Temporal Refinement

• Explicitly maintain an even distribution of
  vertices over the surface by refining mesh.

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Adaptive Refinement

• Our implementation provides two types of mesh
  refinement
• Temporal refine mesh during deformation to
  accurately sample the dynamic surface.
• Painting refine mesh depending on location and
  orientation of brush to accurately sample the
  brush.

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Brush-Dependent Refinement
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Overview of Talk

• Background
• Method
• Applying Paint
• Defining Paint
• Simulating Paint
• Results

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Results
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Results

• Painting interface meets challenges
• Complex Surfaces
• Scale
• User Control

Modeling Time 20 min.
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Results

• Painting interface meets challenges
• Complex Surfaces
• Scale
• User Control

Modeling Time 20 min.
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Results

• Painting interface meets challenges
• Complex Surfaces
• Scale
• User Control

Modeling Time 3 min.
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Conclusion

• We have found that this painting metaphor gives
  the user direct, local control over surface
  deformations for several applications
• Creating new models
• Removing noise from existing models
• Adding geometric texture to an existing surface
  at multiple scales

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Limitations

• Covers limited class of objects.
• Self-intersections.
• Topological changes.

David Breen, et. al.
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Limitations

• Covers limited class of objects.
• Self-intersections.
• Topological changes.

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Limitations

• Covers limited class of objects.
• Self-intersections.
• Topological changes.

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Limitations

• Covers limited class of objects.
• Self-intersections.
• Topological changes.

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Future Work

• Adaptive level sets.
• Transfering geometric texture from one part of a
  model to another.
• Expressing geometric content as paint for
  compression applications.
• Time-dependent pigment vectors (e.g. spline
  curves on a sphere).

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Acknowledgements

• Ross Whitakers VISPACK
• Daniel Aliaga

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Applying Paint Level Sets
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Level Sets Details

• Level Set Theory tells us how to change the
  samples to induce some desired change in the
  embedded surface.

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Level Sets Details

• Fundamental result from LS theory.
• F() is the speed of the surface at position x in
  the direction of its normal vector!

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Mesh Refinement

• Maintain desired edge length.
• f actual/desired
• f lt 0.5 collapse
• f gt 1.5 split
• Swap to maximize minimum interior angle.

Markosian, et. al.