1. Relief: A Modeling by Drawing Tool David Bourguignon 1 Raphaëlle Chaine 2 Marie-Paule Cani 3 George Drettakis 4 1 Princeton University / INRIA Rocquencourt 2 LIRIS / CNRS / UCBL 3 GRAVIR / INP Grenoble 4 REVES / INRIA Sophia-Antipolis

2. Outline Motivation Previous Work Tool Workflow Reconstruction Adaptive Sampling & Depth Inference Tool Interface Results

3. On Users Most people draw –Writing alternative Few people sculpt –Play-Doh days long gone –Materials difficult to handle

4. Goals Use 2D tools to perform 3D operations

5. Goals Use 2D tools to perform 3D operations Model global and local surface

6. Goals Use 2D tools to perform 3D operations Model global and local surface Input: just plain strokes

7. Goals Use 2D tools to perform 3D operations Model global and local surface Input: just plain strokes Output: triangle mesh

8. Outline Motivations Previous Work Tool Workflow Reconstruction Adaptive Sampling & Depth Inference Tool Interface Results

9. Previous Work Depth painting [Williams, 1990] +

10. Previous Work Gradient editing [van Overveld, 1996]

11. Previous Work Maya 6.0 Artisan [Alias, 2004]

12. Outline Motivations Previous Work Tool Workflow Reconstruction Adaptive Sampling & Depth Inference Tool Interface Results

13. Tool Workflow First step: drawing input –Displacement map mid-grey = 0 white > 0 black < 0 Model of 3D sphere Pencil Brush

14. Tool Workflow First step: drawing –Displacement map –2D shape boundary (in green) defines drawing mask

15. Tool Workflow First step: drawing –Displacement map –2D shape boundary –Displacement regions (from 2 maps)

16. Tool Workflow Second step: modeling –Displace existing vertices

17. Tool Workflow Second step: modeling –Displace existing vertices –Create new surface patch

18. Tool Workflow Changing viewpoint Modeling by drawing Changing viewpoint

19. Reconstruction Based on evolving pseudo-manifold [Chaine, 2003]

20. Reconstruction Based on evolving pseudo-manifold [Chaine, 2003] Satisfy our requirements –Arbitrary number of connected components

21. Reconstruction Based on evolving pseudo-manifold [Chaine, 2003] Satisfy our requirements –Arbitrary number of connected components –Handle points off shape boundary

22. Reconstruction Based on evolving pseudo-manifold [Chaine, 2003] Satisfy our requirements –Arbitrary number of connected components –Handle points off shape boundary –Interactive (5k points per second)

23. 2D reconstruction Start: pseudo-curve lies on oriented edges of Delaunay triangulation

24. 2D reconstruction During: pseudo-curve evolves as long as oriented Gabriel criterion is not met

25. 2D reconstruction Stop: topologically consistent set of oriented edges

26. Sampling and Depth Adaptive sampling –Displacement map Pencil and brush data in color buffer Color buffer

27. Sampling and Depth Adaptive sampling –Displacement map –Approximate disp. map sampled at existing vertices

28. Sampling and Depth Adaptive sampling –Displacement map (D) –Vertex-Sampled disp. map (V) –Error map E = 1 – ABS(D – V) –Arbitrary error value

29. Sampling and Depth Adaptive sampling –Displacement map –Approximate disp. map –Error map –Sampling [Alliez, 2002]

30. Sampling and Depth Adaptive sampling Depth inference –Identify surface vertices Vertices ID buffer

31. Sampling and Depth Adaptive sampling Depth inference –Identify surface vertices –Assign depth values Depth buffer

32. Sampling and Depth Adaptive sampling Depth inference –Identify surface vertices –Assign depth values –Infer depth values from existing surface by depth propagation

33. Outline Motivations Previous Work Tool Workflow Reconstruction Adaptive Sampling & Depth Inference Tool Interface Results

34. Tool Interface Hole marks –Comic books production Hole marks Stone #3 (Avalon Studios)

35. Tool Interface Hole marks –Comic books production –Our system Hole mark

36. Tool Interface Video: Basic interface

37. Tool Interface Blobbing DrawingWhite shadingDistance fieldHeight fieldSurface

38. Tool Interface Depth modes (chosen by menu) Modeling “at depth”Depth inferenceFrisket mode

39. Video Modeling a tree Paper sketch3D model obtained with Relief

40. Outline Motivations Previous Work Tool Workflow Reconstruction Adaptive Sampling & Depth Inference Tool Interface Results

41. Models (1k to 4k points)

42. Discussion Intuitive shading convention

43. Discussion Intuitive shading convention Problems with drawing metaphor –No continuous visual feedback Provide two modes

44. Discussion Intuitive shading convention Problems with drawing metaphor –No continuous visual feedback –Difficult to obtain continuous shading Provide higher-level drawing tools

45. Conclusion Modeling by drawing, but imprecise

46. Conclusion Modeling by drawing, but imprecise Future work –Speedup with local 3D reconstruction

47. Conclusion Modeling by drawing, but imprecise Future work –Speedup with local 3D reconstruction –Improve depth inference

48. Conclusion Modeling by drawing, but imprecise Future work –Speedup with local 3D reconstruction –Improve depth inference –Image-space and object-space sampling

49. Acknowledgements This work has been performed while the first author was a visiting research fellow at Princeton University, supported by an INRIA post-doctoral fellowship. Many people have indirectly contributed to it. We would like to thank: Adam Finkelstein, Szymon Rusinkiewicz, Jason Lawrence, Pierre Alliez, Mariette Yvinec, Laurence Boissieux, Laure Heïgéas, Laks Raghupathi, Olivier Cuisenaire, Bingfeng Zhou.

52. Reconstruction Input: shape from strokes –2D reconstruction –3D reconstruction

53. Problems to be solved Provide appropriate drawing rep. –Shape from strokes

54. Tool Workflow Second step: modeling –Adaptive sampling

55. Tool Workflow Second step: modeling –Adaptive sampling –Depth inference

56. Our Approach Provide appropriate drawing rep. –Shape from strokes –Displacement from shading White/black metaphor for displacement Rafaello Sanzio

57. Our Approach Provide appropriate drawing rep. Provide appropriate surface rep. –Free-form appearance

58. Our Approach Provide appropriate drawing rep. –2D Shape from strokes

59. Our Approach Provide appropriate drawing rep. Provide appropriate surface rep. –Free-form appearance –Arbitrary topology changes

60. Outline Motivations Previous Work Contributions Results

61. Contributions Overview Curve and surface reconstruction

62. Contributions Overview Curve and surface reconstruction Adaptive sampling and depth inference

63. Contributions Overview Curve and surface reconstruction Adaptive sampling and depth inference Modeling by drawing interface

64. On Users Most people draw –Writing alternative

65. On Users Most people draw –Writing alternative –Minimal tool set

66. On Users Most people draw –Writing alternative –Minimal tool set –Since kindergarten

67. On Users Most people draw Few people sculpt –Play-Doh days long gone

68. Previous Work Wireframe reconstruction [Lipson, 1996]

69. Previous Work Gesture-based interfaces [Zeleznik, 1996][Igarashi, 1999]

70. Conclusion Modeling by drawing, but imprecise Future work –Speedup with local 3D reconstruction –Modeling alternative for “thin parts” CurrentAlternative“Thin parts”