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Page 1
Applications of Computer Graphics
in Cel Animation
Applications of Applications of Computer GraphicsComputer Graphics
in Cel Animationin Cel Animation
Adam FinkelsteinPrinceton University
COS 426 Spring 2003
Adam FinkelsteinAdam FinkelsteinPrinceton UniversityPrinceton University
COS 426 Spring 2003COS 426 Spring 2003
3-D and 2-D animation33--D and 2D and 2--D animationD animation
Homer 3-DHomer 3Homer 3--DD Homer 2-DHomer 2Homer 2--DD
Advantages of 3-DAdvantages of 3Advantages of 3--DD
• Complex lighting and shading• Reuse from scene to scene• Automatic in-betweening• Ease of camera motion• Realism• Texture mapping
•• Complex lighting and shadingComplex lighting and shading•• Reuse from scene to sceneReuse from scene to scene•• Automatic inAutomatic in--betweeningbetweening•• Ease of camera motionEase of camera motion•• RealismRealism•• Texture mappingTexture mapping
Advantages of 2-DAdvantages of 2Advantages of 2--DD
• Easier for traditional animators• Simple gestures convey emotion• Art form refined for 80 years
•• Easier for traditional animatorsEasier for traditional animators•• Simple gestures convey emotionSimple gestures convey emotion•• Art form refined for 80 yearsArt form refined for 80 years
Key ideaKey ideaKey idea
Use 3-D methods in 2-D animation!• Expressiveness of 2-D• Technical benefits of 3-D
Use 3Use 3--D methods in 2D methods in 2--D animation!D animation!•• Expressiveness of 2Expressiveness of 2--DD•• Technical benefits of 3Technical benefits of 3--DD
Related workRelated workRelated work
Automating cel animation pipeline[Fekete 95, Robertson 94,
Shantzis 94, Wallace 81]
Hybrid 2D/3D for cel animation[Rademacher 99, Williams 91]
Automating cel animation pipelineAutomating cel animation pipeline[[FeketeFekete 95,95, Robertson 94, Robertson 94,
ShantzisShantzis 94, 94, Wallace 81Wallace 81]]
Hybrid 2D/3D for Hybrid 2D/3D for cel cel animationanimation[[RademacherRademacher 99, Williams 9199, Williams 91]]
Page 2
Two forms of art workTwo forms of art workTwo forms of art work OverviewOverviewOverview
• Introduction• Multiperspective panoramas• Texture mapping• Shadows
•• IntroductionIntroduction•• Multiperspective Multiperspective panoramaspanoramas•• Texture mappingTexture mapping•• ShadowsShadows
Multiperspective Panoramasfor Cel Animation
Multiperspective Multiperspective PanoramasPanoramasfor for Cel Cel Animation Animation
[SIGGRAPH '98]
Daniel WoodAdam Finkelstein
John HughesCraig ThayerDavid Salesin
Daniel WoodDaniel WoodAdam FinkelsteinAdam Finkelstein
John HughesJohn HughesCraig ThayerCraig ThayerDavid David SalesinSalesin
University of WashingtonPrinceton UniversityBrown UniversityDisney Feature Animation
University of WashingtonUniversity of WashingtonPrinceton UniversityPrinceton University
Brown UniversityBrown UniversityDisney Feature Animation Disney Feature Animation
[Pinocchio, 1940][[PinocchioPinocchio, 1940], 1940]
Suggesting a moving cameraSuggesting a moving cameraSuggesting a moving camera
A multiperspective panoramaincorporates many perspectives intoa single locally coherent image.
A moving window slides across the panorama, selecting frames for the animation.
AA multiperspectivemultiperspective panoramapanoramaincorporates many perspectives intoincorporates many perspectives intoa single locally coherent image.a single locally coherent image.
A A moving windowmoving window slides across the slides across the panorama, selecting frames for the panorama, selecting frames for the animation.animation.
Page 3
ObjectiveObjectiveObjective
Given: 3D model and camera path
Create: Panorama and moving windowsuch that the 2D animationresembles the 3D animation
GivenGiven:: 3D model and camera path3D model and camera path
CreateCreate:: Panorama and moving windowPanorama and moving windowsuch that the 2D animationsuch that the 2D animationresembles the 3D animationresembles the 3D animation
1. 3-D scene and camera path1. 31. 3--D scene and camera pathD scene and camera path
2. Panorama and moving window2. Panorama and moving window2. Panorama and moving window 3. Illustrated panorama3. Illustrated panorama3. Illustrated panorama
4. Extracted frames4. Extracted frames4. Extracted frames 5. CG Elements5. CG Elements5. CG Elements
Page 4
Creating a panoramaCreating a panoramaCreating a panorama
• Take snapshots of 3D scene• Arrange snapshots in a plane• Merge snapshots into single image
•• Take snapshots of 3D sceneTake snapshots of 3D scene•• Arrange snapshots in a planeArrange snapshots in a plane•• Merge snapshots into single imageMerge snapshots into single image
Take snapshotsTake snapshotsTake snapshots
Arrange snapshotsArrange snapshotsArrange snapshots Merge snapshotsMerge snapshotsMerge snapshots
Arrange consecutive snapshotsArrange consecutive snapshotsArrange consecutive snapshots
1. Sample points from first snapshot2. Find corresponding points
on second snapshot 3. Align snapshots using a transform
1.1. Sample points from first snapshotSample points from first snapshot2.2. Find corresponding points Find corresponding points
on second snapshot on second snapshot 3.3. Align snapshots using a transformAlign snapshots using a transform
Find corresponding pointsFind corresponding pointsFind corresponding points
Page 5
Align snapshotsAlign snapshotsAlign snapshots
UntrimmedUntrimmedUntrimmed
TrimmedTrimmedTrimmed
LimitationsLimitationsLimitations
Panoramas cannot do it all(e.g., circling centerpiece of table)
Our method does not do it all(e.g., Beauty and the Beast library)
Panoramas cannot do it allPanoramas cannot do it all((e.g.e.g., circling centerpiece of table), circling centerpiece of table)
Our method does not do it allOur method does not do it all((e.g.e.g., , Beauty and the BeastBeauty and the Beast library)library)
HandHand--designeddesigned
AutomaticAutomatic
Page 6
StrengthsStrengthsStrengths
• Wide variety of camera motion• Easy experimentation• Easy CG integration • Illustrator creates detail• Hand-drawn artistic style
•• Wide variety of camera motionWide variety of camera motion•• Easy experimentationEasy experimentation•• Easy CG integration Easy CG integration •• Illustrator creates detailIllustrator creates detail•• HandHand--drawn artistic styledrawn artistic style
Texture Mapping for Cel Animation
Texture Mapping for Texture Mapping for CelCel AnimationAnimation
Wagner CorrêaRob Jensen
Craig ThayerAdam Finkelstein
Wagner Wagner CorrCorrêêaaRob Jensen Rob Jensen
Craig ThayerCraig Thayer
Adam FinkelsteinAdam Finkelstein
Princeton UniversityDisney Feature Animation
Princeton UniversityPrinceton University
Disney Feature Animation Disney Feature Animation
[SIGGRAPH '98]
Traditional cel animationTraditional cel animationTraditional cel animation Textured cel animationTextured Textured celcel animationanimation
The processThe processThe process Input of the warpInput of the warpInput of the warp
Page 7
model markermodel markermodel marker drawing markerdrawing markerdrawing marker
Marker curvesMarker curvesMarker curves Input of the warpInput of the warpInput of the warp
Output of the warp Output of the warp Output of the warp
PP QQ
A pair of marker curves A pair of marker curves A pair of marker curves
P Q
At parameter tAt parameter At parameter tt
M(t) D(t)
QPP
Many parameter values Many parameter values Many parameter values
Q
Page 8
Output of the warpOutput of the warpOutput of the warp Controlling the warpControlling the warpControlling the warp
• Weights• Viewing parameters• Extra markers
•• WeightsWeights•• Viewing parametersViewing parameters•• Extra markersExtra markers
Viewing parametersViewing parametersViewing parameters
upright upright upright
tilted tilted tilted
Extra markersExtra markersExtra markers
withwithwithwithoutwithoutwithout
VideoVideoVideo
LimitationsLimitationsLimitations
Page 9
StrengthsStrengthsStrengths
• Fits into current production pipeline• Little effort per frame• Avoids temporal artifacts• Combines strengths of:
2-D: gestures, timing, anticipation
3-D: texture, occlusion, foreshortening
•• Fits into current production pipelineFits into current production pipeline•• Little effort per frameLittle effort per frame•• Avoids temporal artifactsAvoids temporal artifacts•• Combines strengths of:Combines strengths of:
22--D: D: gestures, timing, anticipationgestures, timing, anticipation
33--D: D: texture, occlusion, foreshorteningtexture, occlusion, foreshortening
Shadows for Cel AnimationShadows for Shadows for
CelCel AnimationAnimation
Lena PetrovicBrian Fujito
Lance WilliamsAdam Finkelstein
Lena PetrovicLena PetrovicBrian Brian Fujito Fujito
Lance WilliamsLance Williams
Adam FinkelsteinAdam Finkelstein
Princeton UniversityDisney Feature Animation
Princeton UniversityPrinceton University
Disney Feature Animation Disney Feature Animation
[SIGGRAPH '00]
MotivationMotivationMotivation
backgroundbackgroundbackground
charactercharactercharacter
scenescenescene
MotivationMotivationMotivation
backgroundbackgroundbackgroundscenescenescene
charactercharactercharacter
MotivationMotivationMotivation
no shadowno shadowno shadow shadowshadowshadow
Shadow MattesShadow MattesShadow Mattes
cast shadows (red) - shadows on background
tone mattes (blue) - character shading
contact shadows (green) - darkness underfoot
cast shadowscast shadows (red)(red) -- shadows on backgroundshadows on background
tone mattes (blue)tone mattes (blue) -- character shadingcharacter shading
contact shadowscontact shadows (green)(green) -- darkness underfootdarkness underfoot
Page 10
Project GoalProject GoalProject Goal
backgroundbackgroundbackground
charactercharactercharacter
shadow mattesshadow mattesshadow mattes
Approach: 3D ModelsApproach: 3D ModelsApproach: 3D Models
2D2D2D 3D3D3D
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering • Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• Rendering Rendering •• CompositingCompositing
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering • Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• Rendering Rendering •• CompositingCompositing
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering• Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• RenderingRendering•• CompositingCompositing
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering• Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• RenderingRendering•• CompositingCompositing
Page 11
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering• Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• RenderingRendering•• CompositingCompositing
Process: OverviewProcess: OverviewProcess: Overview
• Background Construction• Character Inflation• Depth Specification• Specifying Lights• Rendering• Compositing
•• Background ConstructionBackground Construction•• Character InflationCharacter Inflation•• Depth SpecificationDepth Specification•• Specifying LightsSpecifying Lights•• RenderingRendering•• CompositingCompositing
Character InflationCharacter InflationCharacter Inflation
Inflate 3-D shapes using Teddy [Igarashi 99]Inflate 3Inflate 3--D shapes using Teddy [Igarashi 99]D shapes using Teddy [Igarashi 99]
character layercharacter layer 3D model3D model
• Two caveats: perspective & layers•• Two caveats: perspective & layersTwo caveats: perspective & layers
Character InflationCharacter InflationCharacter Inflation
character layercharacter layercharacter layer 3D model3D model3D model
First layerFirst layerFirst layer
Character InflationCharacter InflationCharacter Inflation
Adding a second layerAdding a second layerAdding a second layer
character layerscharacter layerscharacter layers 3D model3D model3D model
Character InflationCharacter InflationCharacter Inflation
Adding a third layerAdding a third layerAdding a third layer
character layerscharacter layerscharacter layers 3D model3D model3D model
Page 12
Character InflationCharacter InflationCharacter Inflation
Obtaining layersObtaining layersObtaining layers
layerslayerslayers 3D model3D model3D modelline artline artline art
Character InflationCharacter InflationCharacter Inflation
camera viewcamera viewcamera view off-angle viewoffoff--angle viewangle view
Depth SpecificationDepth SpecificationDepth Specification
Adjust depth while preserving silhouette Adjust depth while preserving silhouette Adjust depth while preserving silhouette
translationtranslationtranslation shearshearshear
Depth SpecificationDepth SpecificationDepth Specification
camera viewcamera viewcamera view off-angle viewoffoff--angle viewangle view
shearshearshear
CompositingCompositingCompositing
Tone matte (blue) modifies character color.
Other mattes (red & green) darken background.
Tone matte (blue) modifies character color.Tone matte (blue) modifies character color.
Other mattes (red & green) darken background. Other mattes (red & green) darken background.
VideoVideoVideo
33 frames33 frames33 frames 16-frame cycle
1616--frame frame cyclecycle
16-frame cycle
1616--frame frame cyclecycle
Page 13
LimitationsLimitationsLimitations
Manual creation of character layers
No aesthetic controls for:• shadow simplification• shadow stylization
Manual creation of character layers Manual creation of character layers
No aesthetic controls for:No aesthetic controls for:
•• shadow simplificationshadow simplification•• shadow stylizationshadow stylization
StrengthsStrengthsStrengths
• Less human effort than hand-drawn
• Plausible shadows
– even in complex scenes
• Lighting effects:
– animated lights, gobos
• Freedom to experiment with lights
•• Less human effort than handLess human effort than hand--drawndrawn
•• Plausible shadowsPlausible shadows
–– even in complex sceneseven in complex scenes
•• Lighting effects: Lighting effects:
–– animated lights, gobosanimated lights, gobos
•• Freedom to experiment with lightsFreedom to experiment with lights
ConclusionsConclusionsConclusions
3D methods may be used in 2D for:• reducing human effort• achieving new effects
Lines between 3D and 2D are blurring
3D methods may be used in 2D for:3D methods may be used in 2D for:
•• reducing human effortreducing human effort•• achieving new effectsachieving new effects
Lines between 3D and 2D are blurringLines between 3D and 2D are blurring
ConclusionsConclusionsConclusions
Lines between 3D and 2D are blurringLines between 3D and 2D are blurringLines between 3D and 2D are blurring