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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 NPR – Non-photorealistic rendering
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
Applications Art
Applications Comics/ Cartoons
Applications Architecture
Applications Maps
Applications Maps
Applications Medicine
Applications Medicine
Applications Technical Illustrations
Applications Archeology
Toon Shading Toon/Cell Shading: Rendering technique to create cartoon like movies
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
Toon Shading Color computation (object space): surface 1D texture
Toon Shading Silhouettes (Screen Space) • generate Depth map • find discontinuities • generate normal map • find discontinuities
Toon Shading Combination of both silhouette detections ideas: Technical Illustrations:
Sketching Sketching: Automatic method to create computer images that look like and hand-made drawings
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
Computer Sketching Example: Object space approach: • Pseudo-Randomly change length of lines • Cut lines into multiple sub-lines • Move line center
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
Halftoning Algorithm: • Input: Gray scale image • Group pixles ( loss of image resolution) • Compute average intensity • Replace group by dither matrix
Halftoning limited resolution of the human visual system
Error Diffusion Floyd and Steinberg
Screening • Bild Screening: Artisticvariationofthe halftoning algorithm Replacesthe simple dithermatrixbyoneoremorecompleximages
Screening Screening with text
Stippling Stippling: Construct an imageof a large numberofdots
Pointillismus Georges Seurat - Ein Sonntagnachmittag auf der Insel La Grande Jatte
Stippling • Motivation: • Results in very “clean/cold” illustrations • Very time-consuming to create manually • Applications: • Scientific and technical illustrations • Art • Print media
Stippling • Stipple points simulate both tone and texture. • Usually a uniform distribution without any recognizable pattern is used
Stippling Object space: • prioritized line textures
Stippling • Other prioritized line textures
Object / Image Space Stippling Supersampling in screen space surface based anti-aliasing black-and-white stippling