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  • 1. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand An Interactive Artificial Ant Approach to Non-Photorealistic Rendering Y. Semet 1 , U.-M. O’Reilly 2 , F. Durand 2 1: INRIA, France 2: Massachusetts Institute of Technology
  • 2. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Roadmap
    •   Non-Photorealistic Rendering
    •   A local agents metaphor
    •   Individual behaviors, collective outcome
    •   Results: reproduction of 2 traditional NPR styles and more:
      •   Painterly rendering
      •   Pencil Sketching
      •   …
    •   A new take on interactivity
  • 3. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Non-Photorealistic Rendering
    •   Photorealism isn’t always effective or superior
    •   Serving depiction purposes
    •   Taking perception into account
    •   Mimicking artistic media or styles
    •   Applications:
      •   Technical illustration, medical imaging
      •   Entertainment industry
  • 4. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Technical Illustration Example: Phong vs. NPR (Gooch, 98)
  • 5. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Pen & Ink (Winkenbach and Salesin, 96)
  • 6. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand More systematicity and interactivity (Durand, Grabli et al.)
  • 7. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Artificial Life for Graphics
    •   Interactive Artificial Evolution is a good tool for Computer Graphics
    •   Provides convenient and creative exploration
    •   Karl Sims (SIGGRAPH 91)
    •   Artificial Ants and Digital Image Habitats (Ramos, 00)
  • 8. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Rationale
    •   Picture production as a gradual adaptive process of successive trials and errors
    Picasso, The Bull
  • 9. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Rationale (cont.)
    •   Divide and conquer: no global exhaustive, deterministic planning but elementary localized behavior
    •   Drawing primitives (what ants do locally): building blocks
    •   Global pictorial outcome: search space
    •   Browsing this space mediating:
      • Automation
      • User Guidance
      • Emergent Novelty
  • 10. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand How it works
    • Load a picture and an empty canvas
    • Preprocessing: computing environmental maps (gradient, importance, etc.) -> information for ants
    • Colony: tweak global parameters through GUI (# of ants, brush params., etc.)
    • Ants: agents that wander around picture and deposit ink on canvas
    • Interaction loop until user satisfied
    •  
  • 11. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Environmental Maps: luminance and importance
    •   Luminance measures visual impact:
    • L= 0.299r + 0.587g + 0.114b
    •   Importance:user-fed subjective information
  • 12. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Environmental Maps: Gradient
    •   Sobel filtering
    •   Two 3x3 convolutions
    •   Two key edge information:
      •   Magnitude
      •   Orientation
  • 13. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Setting Up a Colony
    •   A colony=a group of ants
    •   Holds global, style tuning parameters:
      •   Navigation parameters (gradient thresholds, angles, jumping policy, etc.)
      •   Marking parameters (brush sizes, stroke length, etc.)
    •   Initialization: ants are randomly placed across the picture
    Suivant Précédent Mettre fin au diaporama
  • 14. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Individual Ants
    •   Localized agent:
      •   Position
      •   Velocity (angle+magnitude)
      •   Memory
    •   Sensing capabilities: source image + 4 maps
    •   Behavior: navigation and marking
    •   Ants = convenient metaphor, not ACO
  • 15. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Behaviors and interaction loop
    •   Simple behaviors: a pair (N,M)
      •   N: Navigation strategy: following edges, moving straight ahead, staying.
      •   M: Marking strategy: smudge, hatch, draw.
    •   Composite behaviors: map local conditions to simple behaviors
      •   IF C THEN (N1,M1) ELSE (N2,M2)
      •   e.g. IF high gradient THEN follow edge and draw black lines ELSE move ahead and draw hatches
    •   Behaviors are mapped to keystrokes
  • 16. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Gradual Interaction
    • Press key K -> ants behave and put ink on empty canvas
    • Observe output:
      • Bad: press Erase key
      • Good but not enough: press K again
      • Good and enough, do something different:
        • Modify parameters, press K again
        • Press other key (e.g. M )
    • Go back to 2 until satisfied
  • 17. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Following edges
    •   Following gradient trails
    •   Starts if gradient if sufficiently high (G(x,y)>T_0)
    •   Continues if trail remains sufficiently strong (G(x,y)>T_1)
    •   If trail vanishes: jump ahead
    •   Memory helps avoiding sharp turns
    •   Typical marking: black lines
    •  
  • 18. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Filling Flat Zones
    •   Typically applied if gradient is low (large flat zones)   Marking: Hatching for light zones, cross-hatching for dark ones   Navigation: straight ahead until underlying color doesn’t correspond anymore
  • 19. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Smudging
    •   Simulation of rubbing one’s finger over a portion of the picture.
    •   Outcome is a blurry, more uniform zone
    •   Navigation: usually none
    •   Uses luminance (or color) averaged over a small neighborhood as ink color for round brush strokes
  • 20. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Painterly rendering: state of the art Haeberli, 90 Meier, 96 Hertzmann, 98
  • 21. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Painterly rendering: our heuristics
    •   Large and thick strokes first to cover whole canvas   Gradually finer strokes to reach smaller details   Smudging to blur boundaries between strokes
    •   No edge marking
  • 22. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Painterly Rendering: Sample Output
  • 23. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Other Examples
  • 24. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Pencil Sketching (Sousa&Buchanan)
  • 25. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Pencil Sketching: our heuristic
    •   Strokes that decrease in size while they increase in contrast: simulating the sketching process
    •   Very light or no filling
    •   Hatching/Cross-Hatching
    •   Smudging
  • 26. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Pencil Sketching: Sample Output
  • 27. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand
  • 28. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Other Examples
  • 29. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Combining Styles
  • 30. GECCO'04 - Interactive Ants for NPR - Semet, O'Reilly,Durand Conclusions
    •   A convenient and creative agent-based interactive system
    •   Reproduces 2 existing NPR styles and more.
    •   Ahead: stigmergic communication, genetic browsing.
    •   A new take on interactive adaptive design