1 / 53

Computer-Generated Watercolor

Computer-Generated Watercolor. Cassidy J. Curtis Sean E. Anderson Joshua E. Seims Kurt W. Fleischer David H. Salesin. Outline. Introduction Related work Background Overview Watercolor simulation Rendering Applications Results Conclusion. Introduction.

emerson-morin
Download Presentation

Computer-Generated Watercolor

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Computer-Generated Watercolor Cassidy J. Curtis Sean E. Anderson Joshua E. Seims Kurt W. Fleischer David H. Salesin

  2. Outline • Introduction • Related work • Background • Overview • Watercolor simulation • Rendering • Applications • Results • Conclusion

  3. Introduction • Various artistic effects of watercolor

  4. Related work • Simulating artists’ traditional media and tools • Watercolor : [David Small 1991] • Sumie : [Guo and Kunii 1991] • Commercial package • Fractal Design Painter

  5. Background • Properties of watercolor • Watercolor paper • Pigment • Binder • Surfactant

  6. Background • Watercolor Effects • a) dry-brush • b) Edge darkening • c) Backruns • d) granulation and separation of pigments • e) Flow patterns • f) color glazing

  7. Overview • Computer-generated watercolor 1. Fluid (and pigment) simulation for each glaze 2. Rendering Glaze: physical properties, area

  8. Fluid simulation • Three-layer model

  9. Fluid simulation • Paper Generation • Height field model ( 0 < h < 1 ) • Based on pseudo-random process • Fluid capacity c: proportional to h

  10. Moving Water For each time step Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Main loop

  11. Moving Water For each time step Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Main loop

  12. Moving Water Navier-Stoke Eq. Moving Pigments Viscous drag k Transferring Pigments Paper slope h Applying Capillary Flow Mass conserv. Flow outward Moving water • conditions of water 1. To remain within the wet-area mask 2. To flow outward into nearby region 3. To be damped to minimize oscillating waves 4. To be perturbed by the texture of the paper 5. To be affected by local changes 6. To present the edge-darkening effect

  13. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Configuration • Staggered grid i,j

  14. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Updating the water velocities • Governing Equation (2D Navier-Stoke Eqn.)

  15. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Derivation of Navier-Stoke Eqn.(1/5) • Basic Eqn.: • For unit volume:

  16. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Control volume solid fluid Fluid simulation • Derivation of Navier-Stoke Eqn.(2/5) • Two kind of measurements

  17. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Derivation of Navier-Stoke Eqn.(3/5) • Eulerian view

  18. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Derivation of Navier-Stoke Eqn.(4/5) • Governing Eq.: • Forces: • Gravity: • Viscosity: • Pressure:

  19. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Derivation of Navier-Stoke Eqn.(5/5) • Navier-Stoke Eqn. • For 2D case,

  20. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Updating the water velocities • Numerical integration for u

  21. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Updating the water velocities • Applying paper slope effect: • Applying Drag Force:

  22. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Mass conservation (1/3) • Divergence free condition

  23. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Mass conservation (2/3) • Relaxation (iterative procedure)

  24. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Mass conservation (3/3) • Relaxation (iterative procedure)

  25. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Edge darkening • To flow outward • Remove some water at the boundary

  26. Moving Water Moving Pigments 0 0 0 1 1 1 0 .1 .4 .6 .9 1 0 0 0 1 1 1 0 .1 .4 .6 .9 1 0 0 0 1 1 1 0 .1 .4 .6 .9 1 Transferring Pigments M M’ 0 0 0 .4 .1 0 Applying Capillary Flow 0 0 0 .4 .1 0 0 0 0 .4 .1 0 (1-M’)M Fluid simulation • Edge darkening dry wet

  27. Moving Water For each time step Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Main loop

  28. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Moving Pigments • To move as specified by the velocity field u,v

  29. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Moving Pigments • To move as specified by the velocity field u,v

  30. Moving Water For each time step Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Main loop

  31. Moving Water Moving Pigments Adsorption Transferring Pigments Applying Capillary Flow Desorption Fluid simulation • Transferring Pigments • Adsorption and desorption

  32. Moving Water For each time step Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Main loop

  33. Moving Water Moving Pigments Transferring Pigments Applying Capillary Flow Fluid simulation • Backruns • Diffusing water through the capillary layer • Spreading slowly into a drying region • Transfer water to its dryer neighbors until they are saturated

  34. Fluid simulation • Drybrush effect • By excluding any lower pixel than threshold

  35. Rendering • Optical properties of pigments • Optical composition – subtractive color mixing

  36. S backscattered absorbed K Rendering • Optical properties of pigments • Kubelka-Munk (KM) Model • To compute Reflectance R and Transmittance T using K and S unit length

  37. Rendering • Optical properties of pigments • Kubelka-Munk (KM) Model

  38. Rendering • Optical properties of pigments • Kubelka-Munk (KM) Model • For multiple layers

  39. Rendering • Optical properties of pigments • Kubelka-Munk (KM) Model We need S and K values Make user choose them intuitively

  40. Rendering • Optical properties of pigments • User selects Rw and Rb

  41. Rendering • Optical properties of pigments • User selects Rw and Rb

  42. Applications • 1. Interactive painting with watercolors • 2. Automatic image “watercolorization” • 3. Non-photorealistic rendering of 3D models

  43. Applications • 1. Interactive painting with watercolors

  44. Applications • 2. Automatic image “watercolorization” • Color separation • Brushstroke Planning

  45. Applications • 2. Automatic image “watercolorization” • Color separation • Determine the thickness of each pigment by brute-force search for all color combinations

  46. Applications • 2. Automatic image “watercolorization” • Brushstroke planning

  47. Applications • 3. Non-photorealistic rendering of 3D models • Using “photorealistic” scene of 3D model

  48. Results

  49. Results

  50. Results

More Related