D animation. Advantages of 3-D3. Advantages of 2-D2. Related work. Key idea. Applications of Computer Graphics in Cel Animation.

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1 Applications of Computer Graphics in Cel Animation 3-D D and 2-D 2 D animation Adam Finkelstein Princeton University Homer 3-D3 Homer 2-D2 Advantages of 3-D3 Complex lighting and shading Reuse from scene to scene Automatic in-betweening Ease of camera motion Realism Texture mapping Advantages of 2-D2 Easier for traditional animators Simple gestures convey emotion Art form refined for 80 years Key idea Use 3-D3 D methods in 2-D2 D animation! Expressiveness of 2-D2 Technical benefits of 3-D3 Related work Automating cel animation pipeline [Fekete 95, Robertson 94, Shantzis 94, Wallace 81] Hybrid 2D/3D for cel animation [Rademacher 99, Williams 91] Page 1

2 Two forms of art work Overview Introduction Multiperspective panoramas Texture mapping Shadows Multiperspective Panoramas for Cel Animation Daniel Wood Adam Finkelstein John Hughes Craig Thayer David Salesin University of Washington Princeton University Brown University Disney Feature Animation [SIGGRAPH '98] [Pinocchio,, 1940] Suggesting a moving camera A multiperspective panorama incorporates many perspectives into a single locally coherent image. A moving window slides across the panorama, selecting frames for the animation. Page 2

3 Objective Given: 3D model and camera path Create: Panorama and moving window such that the 2D animation resembles the 3D animation 1. 3-D 3 D scene and camera path 2. Panorama and moving window 3. Illustrated panorama 4. Extracted frames 5. CG Elements Page 3

4 Creating a panorama Take snapshots of 3D scene Arrange snapshots in a plane Merge snapshots into single image Take snapshots Arrange Arrange snapshots snapshots Merge Merge snapshots snapshots Arrange consecutive snapshots Sample Sample points points from from first first snapshot snapshot Find Find corresponding corresponding points points on on second second snapshot snapshot Align Align snapshots snapshots using using aa transform transform Find corresponding points Page 4

5 Untrimmed Trimmed Align snapshots Limitations HandHanddesigned Panoramas Panoramas cannot cannot do do it it all all ((e.g., e.g., e.g., circling circling centerpiece centerpiece of of table) table) Our Our method method does does not not do do it it all all ((e.g., e.g., e.g., Beauty Beauty and and the the Beast Beast library) library) Automatic Page 5

6 Strengths Wide variety of camera motion Easy experimentation Easy CG integration Illustrator creates detail Hand-drawn drawn artistic style Texture Mapping for Cel Animation Wagner Corrêa Rob Jensen Princeton University Craig Thayer Disney Feature Animation Adam Finkelstein [SIGGRAPH '98] Traditional cel animation Textured cel animation The process Input of the warp Page 6

7 Marker curves Input of the warp model marker drawing marker Output of the warp A pair of marker curves P Q P Q At parameter t Many parameter values P Q P Q M(t) D(t) Page 7

8 Output of the warp Controlling the warp Weights Viewing parameters Extra markers Viewing parameters Extra markers upright tilted without with Limitations Video Page 8

9 Strengths Shadows for Cel Animation Fits Fits into into current current production production pipeline pipeline Little Little effort effort per per frame frame Lena Petrovic Avoids Avoids temporal temporal artifacts artifacts Brian Fujito Lance Williams Combines Combines strengths strengths of: of: Princeton University Disney Feature Animation Adam Finkelstein 22-D: -D: gestures, gestures, timing, timing, anticipation anticipation 33-D: -D: texture, texture, occlusion, occlusion, foreshortening foreshortening [SIGGRAPH '00] Motivation Motivation character character scene scene background background Motivation Shadow Mattes cast cast shadows shadows (red) (red) -- shadows shadows on on background background tone tone mattes mattes (blue) (blue) -- character character shading shading contact contact shadows shadows (green) (green) -- darkness darkness underfoot underfoot no shadow shadow Page 9

10 Project Goal Approach: 3D Models character 2D 3D background shadow mattes Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Page 10

11 Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Process: Overview Background Construction Character Inflation Depth Specification Specifying Lights Rendering Compositing Character Inflation Inflate 3-D3 D shapes using Teddy [Igarashi 99] Two caveats: perspective & layers Character Inflation First layer character layer 3D model character layer 3D model Character Inflation Adding a second layer Character Inflation Adding a third layer character layers 3D model character layers 3D model Page 11

12 Character Inflation Character Inflation Obtaining Obtaining layers layers line art layers 3D model camera view Depth Specification Depth Specification shear Adjust Adjust depth depth while while preserving preserving silhouette silhouette translation off-angle view off off-angle shear camera view Compositing off-angle view off off-angle Video Tone Tone matte matte (blue) (blue) modifies modifies character character color. color. Other Other mattes mattes (red (red & & green) green) darken darken background. background. 33 frames Page frame frame cycle 16-frame frame cycle

13 Limitations Manual creation of character layers No aesthetic controls for: shadow simplification shadow stylization Strengths Less human effort than hand-drawn drawn Plausible shadows even in complex scenes Lighting effects: animated lights, gobos Freedom to experiment with lights Conclusions Conclusions 3D methods may be used in 2D for: reducing human effort achieving new effects Lines between 3D and 2D are blurring Lines between 3D and 2D are blurring Page 13