sculpting meshes with self-adaptive topology

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Freestyle

Lucian Stanculescu a,b , Raphaëlle Chaine a , Marie-Paule Cani b,c

a LIRIS, University of Lyon, Franceb LJK, University of Grenoble, Francec INRIA, France

Contents

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1. Introduction

2. Quasi-uniform mesh

3. Time evolution

4. Sculpting tools

5. Results

6. Conclusion and future work

7. Demo

1. Introduction

2. Quasi-uniform mesh

3. Time evolution

4. Sculpting tools

5. Results

6. Conclusion and future work

7. Demo

1. Introduction

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- Goal : Develop an intuitive sculpting system• professional artists and amateur users

- Digital sculpting : important tool for 3D content creation• animated movies, special effects, computer games

- Models behind professional applications :

• polygonal (no changes in topological genus)• ZBrush, Mudbox, Sculptris, Blender

• regular grids (surface extraction, no color)• 3D Coat

- Specific workflow• limitations

- Goal : Develop an intuitive sculpting system• professional artists and amateur users

- Digital sculpting : important tool for 3D content creation• animated movies, special effects, computer games

- Models behind professional applications :

• polygonal (no changes in topological genus)• ZBrush, Mudbox, Sculptris, Blender

• regular grids (surface extraction, no color)• 3D Coat

- Specific workflow• limitations

1. Introduction :: related work

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- Grid-based methods (Galyean and Hughes ‘91)• Deformation tools (Ferley et al. ‘01), virtual clay (Dewaele et al. ‘04)• Surface extraction

- Implicit methods : Blob Tree• Deformations by Warp Curves (Sugihara et al. ‘10)• Hierarchy of tools

- Particle systems (Pons and Boissonnat ‘07, Debard et al. ‘07)• topology changes, quality adaptive mesh – relaxation process slow

- Mesh-based• Model-based deformations : Laplacian editing (Sorkine et al. ‘04)• Space deformations (Angelidis et al. ‘04, von Funck et al. ‘06)• No change in topology

- Grid-based methods (Galyean and Hughes ‘91)• Deformation tools (Ferley et al. ‘01), virtual clay (Dewaele et al. ‘04)• Surface extraction

- Implicit methods : Blob Tree• Deformations by Warp Curves (Sugihara et al. ‘10)• Hierarchy of tools

- Particle systems (Pons and Boissonnat ‘07, Debard et al. ‘07)• topology changes, quality adaptive mesh – relaxation process slow

- Mesh-based• Model-based deformations : Laplacian editing (Sorkine et al. ‘04)• Space deformations (Angelidis et al. ‘04, von Funck et al. ‘06)• No change in topology

1. Introduction :: objective

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Enable topological changes in mesh models• Interactive

Why meshes ?

• No relaxation and complex reconstruction

• Large variety of tools

• Fast rendering on GPU

Enable topological changes in mesh models• Interactive

Why meshes ?

• No relaxation and complex reconstruction

• Large variety of tools

• Fast rendering on GPU

Main idea : manifold mesh with uniform sampling

Advantages :

• Simplify collision detection

• Easily handle changes in topology

• Simple tracking of surface deformations

Main idea : manifold mesh with uniform sampling

Advantages :

• Simplify collision detection

• Easily handle changes in topology

• Simple tracking of surface deformations

2. Quasi-uniform mesh

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D1. Δ tight mesh – closed manifold mesh M with edges < Δ

Constructed by splitting edges > Δ

Advantage: vertices reflect geometry (precision Δ : detail)

edge split

D1. Δ tight mesh – closed manifold mesh M with edges < Δ

Constructed by splitting edges > Δ

Advantage: vertices reflect geometry (precision Δ : detail)

edge split

2. Quasi-uniform mesh :: detail

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D2. Compliance with d • iterate over all edges• collapse if edge < d

! Favored for most edges but not guaranteed

edge collapse

D2. Compliance with d • iterate over all edges• collapse if edge < d

! Favored for most edges but not guaranteed

edge collapse

2. Quasi-uniform mesh :: mesh quality

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D3. Quasi-uniform mesh• d < Δ , closed manifold mesh M• compliance with d• restoration of Δ tightness.

d < Δ / 2d : better uniformity, increase in vertex creation-deletion events

D3. Quasi-uniform mesh• d < Δ , closed manifold mesh M• compliance with d• restoration of Δ tightness.

d < Δ / 2d : better uniformity, increase in vertex creation-deletion events

2. Quasi-uniform mesh

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Vertices displaced by deformation fields• Apply compliance with d• Restore Δ tightness• Handle topology

Difficulty Detect important events before :

• Loss in detail• Self-intersection

Vertices displaced by deformation fields• Apply compliance with d• Restore Δ tightness• Handle topology

Difficulty Detect important events before :

• Loss in detail• Self-intersection

3. Time evolution

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D4. Θ : minimum thickness supported by quasi-uniform mesh

Θ : minimum distance between two non-adjacent vertices.

Simple collisions : vertex-vertex

connecting 1-rings

D4. Θ : minimum thickness supported by quasi-uniform mesh

Θ : minimum distance between two non-adjacent vertices.

Simple collisions : vertex-vertex

connecting 1-rings

3. Time evolution

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D5. μ : maximum allowed displacement for a vertex.

4 μ ² ≤ Θ ² - Δ ² / 3

D5. μ : maximum allowed displacement for a vertex.

4 μ ² ≤ Θ ² - Δ ² / 3

3. Time evolution

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Difficulty : maintain manifold mesh

Neighbourhood cleanup

Handle degenerate cases

• Delete coinciding triangles (a)

• Split surface at coinciding vertices and edges (a, b)

a) b)

Difficulty : maintain manifold mesh

Neighbourhood cleanup

Handle degenerate cases

• Delete coinciding triangles (a)

• Split surface at coinciding vertices and edges (a, b)

a) b)

3. Time evolution

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Displacement fields

• Space deformationsvolume preserving

• Model dependentnormals, geodesic distance…

Deformation applied discretely

Large displacements• divided• max(norm) < μ

Displacement fields

• Space deformationsvolume preserving

• Model dependentnormals, geodesic distance…

Deformation applied discretely

Large displacements• divided• max(norm) < μ

4. Sculpting tools

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4. Sculpting tools :: space

Sweep deform (volume preserving) Sweep deform (volume preserving)

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4. Sculpting tools :: model

Inflate (normals) Inflate (normals)

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Object : 30k points

Collision detection – most time expensiveGPU implementation (x 30 speed-up, Le Grand, GPU Gems 3)

Interactive ~200k pointsno optimization (VBO regions, GPU collision)

Object : 30k points

Collision detection – most time expensiveGPU implementation (x 30 speed-up, Le Grand, GPU Gems 3)

Interactive ~200k pointsno optimization (VBO regions, GPU collision)

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deformation created deleted FPSsweep 19526 13398 15.09

sweep V 21821 17395 15.92inflate 19578 11239 185.82

deflate 9407 7333 238.69grow 14668 9522 43.12trim 422 582 56.13

5. Results

Handle arbitrary changes in topologysimple quasi-uniform framework

Intuitive model based on two physical properties of materialssurface detail and bulk thickness

Closer to real-life sculptingauto-refinementchanges in topology

Handle arbitrary changes in topologysimple quasi-uniform framework

Intuitive model based on two physical properties of materialssurface detail and bulk thickness

Closer to real-life sculptingauto-refinementchanges in topology

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6. Conclusions

• Sharp features

• Sculpting curves

• Fast approximate Boolean operations

• Surface painting

• Adaptive sampling (local quasi-uniform meshes)

• Further validation by professional and amateur users

• Sharp features

• Sculpting curves

• Fast approximate Boolean operations

• Surface painting

• Adaptive sampling (local quasi-uniform meshes)

• Further validation by professional and amateur users

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6. Future work

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7. Demo

Thank you !

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