３Ｄ physics-based brush model for painting

Tokyo Institute of TechnologyTokyo Institute of Technology

Suguru Saito, Masayuki NakajimaSuguru Saito, Masayuki Nakajima

Tokyo Institute of TechnologyTokyo Institute of Technology

Suguru Saito, Masayuki NakajimaSuguru Saito, Masayuki Nakajima

Contents

BackgroundBackground

Related workRelated work

PurposePurpose

Explanation of our brush modelExplanation of our brush model

Experiment & Painting resultExperiment & Painting result

Conclusion & Future workConclusion & Future work

BackgroundBackground

Related workRelated work

PurposePurpose

Explanation of our brush modelExplanation of our brush model

Experiment & Painting resultExperiment & Painting result

Conclusion & Future workConclusion & Future work

Background

Picasso

Musashi Miyamoto

Background

Expressive strokes are important Expressive strokes are important

•strong, sharp, soft, smoothstrong, sharp, soft, smooth

Real brushes can answer feelings of Real brushes can answer feelings of painterspainters

Expressive strokes are important Expressive strokes are important

•strong, sharp, soft, smoothstrong, sharp, soft, smooth

Real brushes can answer feelings of Real brushes can answer feelings of painterspainters

Background

Limit of stroke shape by disc base method Limit of stroke shape by disc base method Limit of stroke shape by disc base method Limit of stroke shape by disc base method

Major drawing technique Major drawing technique

Disc based methodsDisc based methods

•merit of calculationmerit of calculation

– fast, easy algorithmfast, easy algorithm

•limit of Stroke shapelimit of Stroke shape

– Turning point, finishing point Turning point, finishing point

Major drawing technique Major drawing technique

Disc based methodsDisc based methods

•merit of calculationmerit of calculation

– fast, easy algorithmfast, easy algorithm

•limit of Stroke shapelimit of Stroke shape

– Turning point, finishing point Turning point, finishing point

Background

Related Work

For input of variety and expressive strokesFor input of variety and expressive strokes

•fatten center curve algorithmfatten center curve algorithm– Strassmann et.al.[1986]Strassmann et.al.[1986]

– limit of stroke shapelimit of stroke shape•texture mapping based algorithmtexture mapping based algorithm

– Hus et.al.[1994]Hus et.al.[1994]

– different input style to real brushdifferent input style to real brush

For input of variety and expressive strokesFor input of variety and expressive strokes

•fatten center curve algorithmfatten center curve algorithm– Strassmann et.al.[1986]Strassmann et.al.[1986]

– limit of stroke shapelimit of stroke shape•texture mapping based algorithmtexture mapping based algorithm

– Hus et.al.[1994]Hus et.al.[1994]

– different input style to real brushdifferent input style to real brush

Related Work

For input of variety and expressive strokesFor input of variety and expressive strokes

•physics-based brush modelphysics-based brush model– Lee[1999]Lee[1999]

– tuft’s footprint becomes a line segment…tuft’s footprint becomes a line segment…

For input of variety and expressive strokesFor input of variety and expressive strokes

•physics-based brush modelphysics-based brush model– Lee[1999]Lee[1999]

– tuft’s footprint becomes a line segment…tuft’s footprint becomes a line segment…

Purpose

Is to propose a new input technique for Is to propose a new input technique for interactive paintinginteractive painting

1) allows to draw expressive strokes1) allows to draw expressive strokes

2) enables intuitive and direct operation2) enables intuitive and direct operation

Is to propose a new input technique for Is to propose a new input technique for interactive paintinginteractive painting

1) allows to draw expressive strokes1) allows to draw expressive strokes

2) enables intuitive and direct operation2) enables intuitive and direct operation

Purpose

For 1)For 1)• Three dimensional Three dimensional physics-based tuft modelphysics-based tuft model

For 2)For 2)

• Use of a pen tablet deviceUse of a pen tablet device

For 1)For 1)• Three dimensional Three dimensional physics-based tuft modelphysics-based tuft model

For 2)For 2)

• Use of a pen tablet deviceUse of a pen tablet device

Proposed brush model

•Physical modelingPhysical modeling

•Spine curve & Footprint Spine curve & Footprint

•Liquid movementLiquid movement

•Physical modelingPhysical modeling

•Spine curve & Footprint Spine curve & Footprint

•Liquid movementLiquid movement

Simple structureSimple structureSimple structureSimple structure

Physical modeling

Solve the joint’s angle forSolve the joint’s angle forthe minimum system energythe minimum system energy

•Bending energy of the jointBending energy of the joint

•kinetic energy of the masskinetic energy of the mass

•potential energy of the mass potential energy of the mass

•frictional energyfrictional energy

Posture and PositionPosture and Position

Newton-Raphson technique

Proposed brush model

•Physical modelingPhysical modeling

•Spine curve & FootprintSpine curve & Footprint

•Liquid movementLiquid movement

•Physical modelingPhysical modeling

•Spine curve & FootprintSpine curve & Footprint

•Liquid movementLiquid movement

A spine curve is defined as Bezier curve by 3 coA spine curve is defined as Bezier curve by 3 control pointsntrol pointsA spine curve is defined as Bezier curve by 3 coA spine curve is defined as Bezier curve by 3 control pointsntrol points

Spine curve & Footprint

Then the footprint is derivedThen the footprint is derivedThen the footprint is derivedThen the footprint is derived

Proposed brush model

•Physical modelingPhysical modeling

•Spine curve & Footprint Spine curve & Footprint

•Liquid movementLiquid movement

•Physical modelingPhysical modeling

•Spine curve & Footprint Spine curve & Footprint

•Liquid movementLiquid movement

Virtual structureVirtual structure Virtual structureVirtual structure

Liquid movement

Calculation of movementCalculation of movementdirection in pipe fromdirection in pipe from

•Gravity to liquidGravity to liquid

•absorption force from paperabsorption force from paper

•absorption force from the tuft absorption force from the tuft

Experiment

The relation between the handle posture and The relation between the handle posture and the spine curvethe spine curve

easy control by the handle motioneasy control by the handle motion

The relation between the handle posture and The relation between the handle posture and the spine curvethe spine curve

easy control by the handle motioneasy control by the handle motion

Experiment

Changing footprint shapeChanging footprint shape

Natural response to the handle postureNatural response to the handle postureDynamic drip shapesDynamic drip shapes

Changing footprint shapeChanging footprint shape

Natural response to the handle postureNatural response to the handle postureDynamic drip shapesDynamic drip shapes

SystemHardware: Pentium 450MHzHardware: Pentium 450MHzOS: LinuxOS: LinuxGraphics system: X window systemGraphics system: X window systemGraphic library: gtk+Graphic library: gtk+Input device: wacom pen tabletInput device: wacom pen tablet

Hardware: Pentium 450MHzHardware: Pentium 450MHzOS: LinuxOS: LinuxGraphics system: X window systemGraphics system: X window systemGraphic library: gtk+Graphic library: gtk+Input device: wacom pen tabletInput device: wacom pen tablet

Additional model information for paint tool

Paint model: based on Kubelka-Munk theoryPaint model: based on Kubelka-Munk theory

=> color calculation by=> color calculation by

– paint density, layer thicknesspaint density, layer thickness

=>easy color mixture=>easy color mixture

Paper model: cell arrayPaper model: cell array

cell size = pixel sizecell size = pixel size

cell’s paint capacity: defined by scanned paper texturecell’s paint capacity: defined by scanned paper texture

Paint model: based on Kubelka-Munk theoryPaint model: based on Kubelka-Munk theory

=> color calculation by=> color calculation by

– paint density, layer thicknesspaint density, layer thickness

=>easy color mixture=>easy color mixture

Paper model: cell arrayPaper model: cell array

cell size = pixel sizecell size = pixel size

cell’s paint capacity: defined by scanned paper texturecell’s paint capacity: defined by scanned paper texture

Painting results

Japanese character “kana”Japanese character “kana”Japanese character “kana”Japanese character “kana”

Characteristic drawing at Finishing point,Turning pointCharacteristic drawing at Finishing point,Turning pointexpression of user’s peculiarityexpression of user’s peculiarity

Painting results

A Japanese character ‘kanji’A Japanese character ‘kanji’A Japanese character ‘kanji’A Japanese character ‘kanji’

Tao

Painting results

A Japanese style pictureA Japanese style pictureA Japanese style pictureA Japanese style picture

4 strokes’ painting

Painting results

A Japanese style pictureA Japanese style pictureA Japanese style pictureA Japanese style picture

flowers

Conclusion

A new brush model is proposedA new brush model is proposed

3D physics-based brush model3D physics-based brush model•highly expressive strokehighly expressive stroke

– dynamic change of footprint shape dynamic change of footprint shape

– subtlety gradation by paint liquid quantitysubtlety gradation by paint liquid quantity

•interactiveinteractive　　– direct and intuitive operationdirect and intuitive operation

– natural manner similar to real paintingnatural manner similar to real painting

A new brush model is proposedA new brush model is proposed

3D physics-based brush model3D physics-based brush model•highly expressive strokehighly expressive stroke

– dynamic change of footprint shape dynamic change of footprint shape

– subtlety gradation by paint liquid quantitysubtlety gradation by paint liquid quantity

•interactiveinteractive　　– direct and intuitive operationdirect and intuitive operation

– natural manner similar to real paintingnatural manner similar to real painting

Future work

More complex liquid movementMore complex liquid movement

– scratch stroke, blotting strokescratch stroke, blotting stroke

Visualization of paint quantity in brushVisualization of paint quantity in brush

Improvement of the transformation pressure Improvement of the transformation pressure to ‘z’ valueto ‘z’ value

Complete paint toolComplete paint tool

More complex liquid movementMore complex liquid movement

– scratch stroke, blotting strokescratch stroke, blotting stroke

Visualization of paint quantity in brushVisualization of paint quantity in brush

Improvement of the transformation pressure Improvement of the transformation pressure to ‘z’ valueto ‘z’ value

Complete paint toolComplete paint tool