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

4. Challenges • Complex Surfaces • Scale • User Control

5. 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

7. 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

12. Key Observation Directly “painting” and then interactively simulating is a more controllable, powerful way to locally deform surfaces.

13. 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.

14. 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.

15. 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.

16. Overview of Talk • Introduction • Method • Applying Paint • Defining Paint • Simulating Paint • Results

17. Overview of Talk • Introduction • Method • Applying Paint • Defining Paint • Simulating Paint • Results

18. Applying Paint • Directly inject paint into scene. • Use 2D brush bitmaps to modulate intensity [Hanrahan90]. Various Brushes

19. Applying Paint

20. Applying Paint

21. Overview of Talk • Background • Method • Applying Paint • Defining Paint • Simulating Paint • Results

22. Defining Paint • What is paint? • Paint describes surface velocity

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

24. Surface Velocity • We define surface velocity at some point along the model’s surface x, with surface normal n, as the linear combination of three terms: v(x) = vprop(x) + vadv(x) + vcurv(x)

25. Propagating Velocity • “Propagating” velocity causes the surface to move in the direction of its current surface normal, producing blobby, organic deformations: vprop(x) = αn

26. Propagating Velocity

27. Advective Velocity • “Advective” velocity causes the surface to move at a constant speed in a constant direction: vadv(x) = βp

28. Advective Velocity

29. Curvature-Dependent Velocity • “Curvature-dependent” velocity causes the surface to move at a speed proportional to its mean curvature, κ, in the direction of its surface normal. vcurv(x) = γκn

30. Curvature-Dependent Velocity

31. Specify Paint • Total velocity of a point on the model’s surface: v(x) = αn + βp + γκn

32. Specify Paint • The paint IS the values of α, β, andγ. • The direction of advective motion, p, determined by current viewing direction, surface normal, or arbitrary direction.

33. Overview of Talk • Background • Method • Applying Paint • Defining Paint • Simulating Paint • Results

34. Simulating Paint • Goal: move surface according to velocity user has “painted.”

35. 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

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

37. 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.

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

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

40. 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.

41. Brush-Dependent Refinement

42. Overview of Talk • Background • Method • Applying Paint • Defining Paint • Simulating Paint • Results

43. Results

44. Results • Painting interface meets challenges: • Complex Surfaces • Scale • User Control Modeling Time: 20 min.

45. Results • Painting interface meets challenges: • Complex Surfaces • Scale • User Control Modeling Time: 20 min.

46. Results • Painting interface meets challenges: • Complex Surfaces • Scale • User Control Modeling Time: 3 min.

47. 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

48. Limitations • Covers limited class of objects. • Self-intersections. • Topological changes. David Breen, et. al.

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

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