computer generated watercolor
DESCRIPTION
Computer Generated Watercolor. Curtis, Anderson, Seims, Fleisher, Salesin SIGGRAPH 1997. Presented by Yann SEMET Universite of Illinois at Urbana Champaign Universite de Technologie de Compiegne. Background. NPR Purpose : aesthetic rather than technical Artificial art ?. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/1.jpg)
Computer Generated Watercolor
Curtis, Anderson, Seims, Fleisher, Salesin
SIGGRAPH 1997
Presented byYann SEMET
Universite of Illinois at Urbana ChampaignUniversite de Technologie de Compiegne
![Page 2: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/2.jpg)
Background
NPR Purpose : aesthetic rather than
technical Artificial art ?
![Page 3: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/3.jpg)
Harold Cohen – 80’s
![Page 4: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/4.jpg)
Haeberli - 1990
![Page 5: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/5.jpg)
Meier - 1995
![Page 6: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/6.jpg)
Litwinowicz - 1997
![Page 7: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/7.jpg)
Hertzmann – 1998, 2001
![Page 8: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/8.jpg)
Gooch - 2001
![Page 9: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/9.jpg)
Today : Curtis et al. - 1997
![Page 10: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/10.jpg)
Overview Particularities of Watercolor Computer simulation
Fluid simulation Kubelka-Munk rendering
Applications Discussion
![Page 11: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/11.jpg)
Like no other medium
Beautiful textures and patterns Reveals the motion of water Luminous, glowing
![Page 12: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/12.jpg)
Blake (1757-1827)
![Page 13: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/13.jpg)
Turner (1775-1851)
![Page 14: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/14.jpg)
Constable (1776-1837)
![Page 15: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/15.jpg)
Cezanne (1839-1906)
![Page 16: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/16.jpg)
Kandinski (1866-1944)
![Page 17: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/17.jpg)
Klee (1879-1940)
![Page 18: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/18.jpg)
Carter (1955-)
![Page 19: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/19.jpg)
Watercolor materials
Paper Pigments
![Page 20: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/20.jpg)
Watercolor effects
a) Dry brushb) Edge darkeningc) Back runs
d) Granulatione) Flowf) Glazing
![Page 21: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/21.jpg)
Simulation..
![Page 22: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/22.jpg)
Fluid simulation I 3 layers :
![Page 23: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/23.jpg)
Fluid simulation II Parameters of the simulation :
Wet-area mask : M Velocities : u,v Pressure : p Concentration : gk
Height of paper : h Physical properties : density, staining
power, granularity, etc. Fluid properties : saturation, capacity, etc.
![Page 24: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/24.jpg)
Paper simulation Supposedly : shape of every fiber
matters A simpler model : a height field Generation : Perlin’s noise and
Worley’s cellular textures
![Page 25: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/25.jpg)
Main loop For each time step
Move Water Update velocities Relax Divergence Flow Outward
Move Pigment Transfer Pigment Simulate Capillary Flow
![Page 26: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/26.jpg)
Conditions for realism Flow must be constrained so water
remains within M Surplus of water causes flow outward Flow must be damped to minimize
oscillating waves Flow is perturbed by texture of paper Local changes have global effects Outward flow to darken edges
![Page 27: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/27.jpg)
Rendering : Kubelka-Munk For each pigment, 2 coeff. Per RGB
layer : K : absorbtion S : scattering
Supposedly : K and S are measured Here : user provides Rw and Rb
![Page 28: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/28.jpg)
Types of paints Opaque (e.g. Indian Red) Transparent (e.g. Quinacridone
Rose) Interference (e.g. Interference
Lilac) Different hues (e.g. Hansa Yellow)
![Page 29: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/29.jpg)
Optical compositing Compute R and T :
Then compose :
Weight relatively to relative thicknesses
![Page 30: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/30.jpg)
Discussion of the KM model Assumptions partially satisfied :
Identical refractive indices Random orientation of pigments Diffuse illumination 1 wavelength at a time No chemical interaction
Works surprisingly well ! OK, because we’re looking for
appearance, not actual modeling
![Page 31: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/31.jpg)
Application I Interactive painting :
![Page 32: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/32.jpg)
Application II Watercolorization :
![Page 33: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/33.jpg)
Application III 3D models :
![Page 34: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/34.jpg)
Future work
Other effects Automatic rendering Generalization Animation
![Page 35: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/35.jpg)
Summary
A particular painting technique A physically based simulation
Fluid motion Optical compositing
Application and results
![Page 36: Computer Generated Watercolor](https://reader035.vdocument.in/reader035/viewer/2022062518/56814924550346895db65e59/html5/thumbnails/36.jpg)
Conclusion and discussion
Efficiency issues and long term interest
Border between art, physics and computer science