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SIGG03-npr2d3d

Painters interface uses Digpaint (in-house 2D paint system) BG Painters use a set of reference layers prepared by TD (grey render, outlines ...

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SIGG03-npr2d3d

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  1. NPR - 2D to 3D, painting and rendering Daniel Teece Walt Disney Feature Animation daniel.teece@disney.com

  2. Introduction Coming up… • Background • 2D and 3D brush models • Animation problems and approaches • Examples of NPR used in film production • Sable

  3. NPR Characteristics What defines an NPR system? • “Natural Media Emulation” • 2D / 3D • Interactivity / Artistic direction • Brushes, strokes and marks • Complications - visibility … animation!

  4. NPR Cross-section 2D 3D automatic stroke renderers image processors 2D paint systems 3D paint / renderers interactive

  5. NPR Cross-section 2D 3D automatic Litwinowicz97 Hertzmann00 Hertzmann98 Meier96 Haeberli90 DeepCanvas Teece98 Kalnins02 interactive

  6. 2D Strokes 2D paint strokes and reference images • Images in, images out • Stamp-based, procedural or physically-based • Haeberli’s “Paint by Numbers” [Haeberli90] • Hertzmann’s subsequent improvements [Hertzmann98]

  7. Animating Strokes Finding frame to frame coherence • Stroke placement methods cause temporal artifacts • Locking strokes to canvas improves coherence but can look strange • Strokes should move smoothly, matching motion of subject

  8. Image Space Stroke Animation Optical flow techniques • “Processing images and video for an impressionist effect” [Litwinowicz97] • “Painterly rendering for video and interaction” [Hertzmann00] • Strokes moved, added or removed based on frame-to-frame optical flow data • Strokes retain two-dimensional nature

  9. Brush Models - 3D Strokes and Surfaces • Pixel (texture maps) • Geometry (points & matrices) • Procedure (paths & width vectors) From [Katanics,Lappas99]

  10. Painterly Rendering for Animation [Meier96] A 3D stroke renderer • Particles placed on geometry, based on surface area • Strokes placed at particle positions, with parameters driven by reference renders • Depth sorting and layering for visibility • Smooth stroke animation, with a painterly appearance

  11. 3D Expressive Paint A 3D interactive painting system • Strokes and marks in object space • Developed for animating painterly imagery • Fully interactive • Two types of stroke - 3D geometry and screen aligned

  12. 3D Expressive Paint 3D Strokes are painted interactively by ray-casting in to the stencil scene

  13. 3D Expressive Paint • Paint order / depth order (“clump buffer”) • Silhouettes - coherence & character [Kalnins02] • Brush model - lighting, textures etc. • Limited animation support (e.g. deforming surfaces) • Border or transition strokes between surfaces (back to 2D/3D relationship)

  14. DeepCanvas A 3D painting and rendering system • Painters interface uses Digpaint (in-house 2D paint system) • BG Painters use a set of reference layers prepared by TD (grey render, outlines …) • Strokes are stored in stroke script files, and mapped on to 3D geometry • Renderer ‘re-paints’ scene from new angle

  15. DeepCanvas From [Katanics,Lappas99] A 2D/3D painting and rendering system

  16. DeepCanvas From [Katanics,Lappas99] Simplified stroke representation - stroke spine and width vectors

  17. Sable A 2D/3D stroke renderer • Library of specifically scanned & processed strokes • Operates as a pipeline component with Inka • Stroke paths can be any Inka line type • Workflow designed to be driven by traditional animation

  18. Sable Requirements: • Match look of original artwork (stylized, flat, few strokes, black background) • Retain performance seen in pencil animation • Animate strokes smoothly & efficiently

  19. Sable First attempt - DeepCanvas brush • Utility to convert ink lines to stroke scripts • All pre-written software (except converter) • Problems achieving distinctive look • DeepCanvas procedural brush sensitive to segment distribution

  20. Sable © Disney Animated non-mapped DeepCanvas strokes

  21. Sable Brush model • Texture-based, extracted from example set • Library of textures and shapes • Stroke geometry is grown along spine curve • Sharp twists are problematic … splitting

  22. Sable © Disney

  23. Sable Animation Rigged curve set animated to match traditional animation © Disney

  24. Sable Results © Disney

  25. Sable Summary • Animate strokes smoothly & efficiently • Able to match appearance of strokes • Integration with other tools in pipeline • Animators able to work with a pencil

  26. Conclusions • Combining animation and NPR can be approached with 2D or 3D methods • With 2D, frame-to-frame coherence can be difficult to maintain • With 3D, some operations may detract from the painterly look • Brush models vary, but are important • Interaction and workflow are also important

  27. Acknowledgements • Mike Gabriel • George Katanics • Jack Brooks

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