imagis-gravir / imag drawing for illustration and annotation in 3d david bourguignon*, marie-paule...
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iMAGIS-GRAVIR / IMAG
Drawing for Illustration andAnnotation in 3D
David Bourguignon*, Marie-Paule Cani* and George Drettakis**
*iMAGIS, INRIA Rhône-Alpes, France
**REVES, INRIA Sophia-Antipolis, France
iMAGIS-GRAVIR / IMAG
Motivation•Drawing
– Scene complexity in an effective manner– Indication of uncertainty– Limitation to single
viewpoint
•Applications– Fine arts– Teaching– Early stages of design
Human heart
iMAGIS-GRAVIR / IMAG
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
EyeBack
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
Previous Work[Akeo et al., 1994][Pugh, 1992]
2D drawing is converted to 3D
Specify hidden parts by hand
iMAGIS-GRAVIR / IMAG
Previous Work
[Lipson and Shpitalni, 1996] [Eggli et al., 1997]
No free-form drawing Limited number of primitives
iMAGIS-GRAVIR / IMAG
Previous Work
[Cohen et al., 1999] [Tolba et al., 1999]
3D curves design,no drawing
2D drawings reprojected,no visibility changes
iMAGIS-GRAVIR / IMAG
Previous Work
[Igarashi et al., 1999][Zeleznik et al., 1996]
Limited to a given gestural interface
Closed strokes only
iMAGIS-GRAVIR / IMAG
Previous Work
[Cohen et al., 2000]
Drawing modes adapted to landscaping only,no 3D model reconstruction in billboard mode
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
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)
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG
Silhouette Stroke – Modeling• Infer local surface
– 3D circles from vectors of curvature– Local Bézier surface
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
Silhouette Stroke – Rendering• New silhouette from new viewpoint
– Efficient silhouette approximation using clipping planes
– Good for local surfaces associated with strokes
iMAGIS-GRAVIR / IMAG
Silhouette Stroke – Rendering•Represent uncertainty
– Use stroke texture– Color stroke as desired
Front(original view)
Side (30°)
Side (90°)
Strokealpha texture
iMAGIS-GRAVIR / IMAG
Silhouette Stroke – Rendering•Manage occlusion
– Use occluder texture for soft occlusion– Various drawing styles
Occluderalpha texture
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
Interface for Drawing
•Two types of strokes– Line stroke– Silhouette stroke
•Two drawing modes– In empty space– Relatively to other objects
On one objectBetween two objects
iMAGIS-GRAVIR / IMAG
Overview
• Previous work
• Contributions– Silhouette stroke modeling
– Silhouette stroke rendering
– Interface for drawing
• Results
iMAGIS-GRAVIR / IMAG
Applications• Illustration in 3D
iMAGIS-GRAVIR / IMAG
Applications•Annotation of a 3D scene
iMAGIS-GRAVIR / IMAG
Applications•"Guided design"
iMAGIS-GRAVIR / IMAG
Video
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG
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
iMAGIS-GRAVIR / IMAG