drawing for illustration and annotation in 3d
DESCRIPTION
We present a system for sketching in 3D, which strives to preserve the degree of expression, imagination, and simplicity of use achieved by 2D drawing. Our system directly uses user-drawn strokes to infer the sketches representing the same scene from different viewpoints, rather than attempting to reconstruct a 3D model. This is achieved by interpreting strokes as indications of a local surface silhouette or contour. Strokes thus deform and disappear progressively as we move away from the original viewpoint. They may be occluded by objects indicated by other strokes, or, in contrast, be drawn above such objects. The user draws on a plane which can be positioned explicitly or relative to other objects or strokes in the sketch. Our system is interactive, since we use fast algorithms and graphics hardware for rendering. We present applications to education, design, architecture and fashion, where 3D sketches can be used alone or as an annotation of an existing 3D model.TRANSCRIPT
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