Drawing for Illustration and Annotation in 3D

1
Drawing for Illustration andAnnotation in 3D

• David Bourguignon, Marie-Paule Cani and George
  Drettakis
• iMAGIS, INRIA Rhône-Alpes, France
• REVES, INRIA Sophia-Antipolis, France

2
Motivation

• Drawing
• Scene complexity in an effective manner
• Indication of uncertainty
• Limitation to single
  viewpoint
• Applications
• Fine arts
• Teaching
• Early stages of design

3
Motivation

• Goal drawing in 3D
• Augment strokes to true 3D entities
• Free-form drawing
• Annotation of existing 3D models
• Many viewpoints
• Problems to be solved
• Silhouette stroke modeling
• Silhouette stroke rendering from different
  viewpoints

Eye
Back
4
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

5
Previous Work
Akeo et al., 1994
Pugh, 1992
Specify hidden parts by hand
2D drawing is converted to 3D
6
Previous Work
Lipson and Shpitalni, 1996
Eggli et al., 1997
No free-form drawing
Limited number of primitives
7
Previous Work
Cohen et al., 1999
Tolba et al., 1999
3D curves design, no drawing
2D drawings reprojected, no visibility changes
8
Previous Work
Igarashi et al., 1999
Zeleznik et al., 1996
Closed strokes only
Limited to a given gestural interface
9
Previous Work
Cohen et al., 2000
Drawing modes adapted to landscaping only, no 3D
model reconstruction in billboard mode
10
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

11
Our Approach

• Strokes
• 2D drawing on the screen plane
• Line stroke for 1D details
• Silhouette stroke for view-dependent
  information
• Problems to be solved
• Inferring local surface from silhouette
• Representing uncertainty
• Managing occlusions

Silhouette stroke
Line stroke (3D spline)
12
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

13
Silhouette Stroke Modeling

• Infer local surface
• Fit Bézier curve to 2D user input
• Evaluate local curvature
• Process curvature vectors
• Clamp relatively to inflexion points
• Set consistent in/out orientation

14
Silhouette Stroke Modeling

• Infer local surface
• Fit Bézier curve to 2D user input
• Evaluate local curvature
• Process curvature vectors
• Clamp relatively to inflexion points
• Set consistent in/out orientation

15
Silhouette Stroke Modeling

• Infer local surface
• Fit Bézier curve to 2D user input
• Evaluate local curvature
• Process curvature vectors
• Clamp relatively to inflexion points
• Set consistent in/out orientation

16
Silhouette Stroke Modeling

• Infer local surface
• 3D circles from vectors of curvature
• Local Bézier surface

17
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

18
Silhouette Stroke Rendering

• New silhouette from new viewpoint
• Efficient silhouette approximation using clipping
  planes
• Good for local surfaces associated with strokes

19
Silhouette Stroke Rendering

• Represent uncertainty
• Use stroke texture
• Color stroke as desired

Front (original view)
Side (30)
Side (90)
Stroke alpha texture
20
Silhouette Stroke Rendering

• Manage occlusion
• Use occluder texture for soft occlusion
• Various drawing styles

Occluder alpha texture
21
Silhouette Stroke Rendering

• Multipass algorithm
• (Previously render scene and line strokes)
• First pass Rendering silhouette strokes
• With stroke texture
• With stroke color
• Second pass Soft occlusion by local surfaces
  (set depth)
• With occluder texture
• Third pass Soft occlusion by local surfaces
  (achieve blend)
• With occluder texture
• With occluder color

22
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

23
Interface for Drawing
On one object
Between two objects

• Two types of strokes
• Line stroke
• Silhouette stroke
• Two drawing modes
• In empty space
• Relatively to other objects

24
Overview

• Previous work
• Contributions
• Silhouette stroke modeling
• Silhouette stroke rendering
• Interface for drawing
• Results

25
Applications

• Illustration in 3D

26
Applications

• Annotation of a 3D scene

27
Applications

• "Guided design"

28
Video
29
Conclusion

• System for drawing in 3D
• View-dependent strokes with occlusion
• Useful for drawing simple scenes in 3D
• Useful for annotations
• Future work
• Handling tubular objects
• Real world test using it to teach anatomy

30
Acknowledgements

• Eric Ferley for feedback throughout the project
• Laurence Boissieux for creating some of the
  drawings, Marc Pont for help with models
• Frédo Durand for advice on the paper
• iMAGIS is a joint project of CNRS, INPG, INRIA
  and UJF

31
(No Transcript)