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Image Synthesis

Image Synthesis. NPR – Non-photorealistic rendering. NP vs. NPR?. PR vs. NPR. Why NPR?. Reasons against photorealism?. Too much (unnecessary) information  maps, technical/medical illustrations Constraints Creativity  improper for caricatures, comics , art

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Image Synthesis

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  1. Image Synthesis NPR – Non-photorealistic rendering

  2. NP vs. NPR?

  3. PR vs. NPR

  4. Why NPR?

  5. Reasons against photorealism? • Too much (unnecessary) information maps, technical/medical illustrations • Constraints Creativity improper for caricatures, comics, art • Time consuming image generation (probably) not feasible for real-time applications • No room for the fantasy of the viewer „Photorealism, like pornography, leaves nothing to the imagination“- Cassidy Curtis

  6. Applications Art

  7. Applications Comics/ Cartoons

  8. Applications Architecture

  9. Applications Maps

  10. Applications Maps

  11. Applications Medicine

  12. Applications Medicine

  13. Applications Technical Illustrations

  14. Applications Archeology

  15. Basics

  16. Algorithms

  17. Toon Shading Toon/Cell Shading: Rendering technique to create cartoon like movies

  18. Toon Shading Motivation: Simpel and (semi-) automatic (mass-) production of comics • large homogenous regions • very few colors • enhanced silhouettes • simple geometry • reduction to important elements

  19. Toon Shading Color computation (object space): surface 1D texture

  20. Toon Shading Silhouettes (Screen Space) • generate Depth map • find discontinuities • generate normal map • find discontinuities

  21. Toon Shading Combination of both silhouette detections ideas: Technical Illustrations:

  22. Sketching Sketching: Automatic method to create computer images that look like and hand-made drawings

  23. Computer Sketching Motivation: • Ideal to present concepts (architecture) • Precise Depiction often looks very sterile Methods: • Use special output device • Image space post-processing • Object space 3D model modification

  24. Computer Sketching Example: Object space approach: • Pseudo-Randomly change length of lines • Cut lines into multiple sub-lines • Move line center

  25. Halftoning Halftoning: Reproduce (color/grayscale) images with a (very) limited amount of colors, usually only black/white “Historically”, a necessity to print images in newspapers

  26. Halftoning Algorithm: • Input: Gray scale image • Group pixles ( loss of image resolution) • Compute average intensity • Replace group by dither matrix

  27. Halftoning limited resolution of the human visual system

  28. Error Diffusion Floyd and Steinberg

  29. Screening • Bild Screening: Artisticvariationofthe halftoning algorithm Replacesthe simple dithermatrixbyoneoremorecompleximages

  30. Screening Screening with text

  31. Stippling Stippling: Construct an imageof a large numberofdots

  32. Pointillismus Georges Seurat - Ein Sonntagnachmittag auf der Insel La Grande Jatte

  33. Stippling • Motivation: • Results in very “clean/cold” illustrations • Very time-consuming to create manually • Applications: • Scientific and technical illustrations • Art • Print media

  34. Stippling • Stipple points simulate both tone and texture. • Usually a uniform distribution without any recognizable pattern is used

  35. Stippling Object space: • prioritized line textures

  36. Stippling • Other prioritized line textures

  37. Stippling

  38. Object / Image Space Stippling

  39. Object / Image Space Stippling Supersampling in screen space surface based anti-aliasing black-and-white stippling

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