computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group NP vs.
NPR?
Slide 3
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group PR vs.
NPR
Slide 4
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Why NPR?
Science: Convey information more efficiently by reduction,
abstraction, accentuation Art: create novel artistic, creative
imagery
Slide 5
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group 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
Slide 6
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Art
Slide 7
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Comics/ Cartoons
Slide 8
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Architecture
Slide 9
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Maps
Slide 10
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Maps
Slide 11
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Medicine
Slide 12
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Medicine
Slide 13
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Technical Illustrations
Slide 14
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Applications Archeology
Slide 15
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Basics
Object Space Screen Space 3D 2D Geometry processing Image
processing Object PrecisionScreen Precision Pseudo code: for each
Object do Pseudo code: for each Pixel do Usually does not require
recomputation on affine transformations Recomputation every time
the image changes ( no frame-to-frame coherence Shower Door
Effect)
Slide 16
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Algorithms
Toon/Cell ShadingSketchingHalftoningScreeningStippling
Slide 17
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Toon
Shading Toon/Cell Shading: Rendering technique to create cartoon
like movies
Slide 18
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Toon
Shading -large homogenous regions -very few colors -enhanced
silhouettes -simple geometry -reduction to important elements
Motivation: Simpel and (semi-) automatic (mass-) production of
comics
Slide 19
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Toon
Shading Color computation (object space): precompute 2-3 shades for
each color (Light-/ Shadow- color) and store them in a 1D texture
assignment of final color by 1D texture lookup 1D texture
surface
Slide 20
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Toon
Shading Silhouettes (Screen Space) generate Depth map generate
Depth map find discontinuities find discontinuities generate normal
map generate normal map find discontinuities find
discontinuities
Slide 21
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Toon
Shading Combination of both silhouette detections ideas: Technical
Illustrations :
Slide 22
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Sketching
Sketching: Automatic method to create computer images that look
like and hand-made drawings
Slide 23
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group 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
Slide 24
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Computer
Sketching Example: Object space approach: Pseudo-Randomly change
length of lines Cut lines into multiple sub-lines Move line
center
Slide 25
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group 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
Slide 26
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Halftoning
Algorithm: Input: Gray scale image Group pixles ( loss of image
resolution) Compute average intensity Replace group by dither
matrix294618 735
Slide 27
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Halftoning
limited resolution of the human visual system
Slide 28
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Error
Diffusion Floyd and Steinberg
Slide 29
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Screening
Bild Screening: Artistic variation of the halftoning algorithm
Replaces the simple dither matrix by one ore more complex
images
Slide 30
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Screening
Screening with text
Slide 31
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Stippling
Stippling: Construct an image of a large number of dots
Slide 32
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Pointillismus Georges Seurat - Ein Sonntagnachmittag auf der Insel
La Grande Jatte
Slide 33
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Stippling
Motivation: Results in very clean/cold illustrations Very
time-consuming to create manually Applications: Scientific and
technical illustrations Art Print media
Slide 34
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Stippling
Stipple points simulate both tone and texture. Usually a uniform
distribution without any recognizable pattern is used
Slide 35
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Stippling
Object space: prioritized line textures
Slide 36
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Stippling
Other prioritized line textures
Slide 37
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group
Stippling
Slide 38
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Object /
Image Space Stippling
Slide 39
computer graphics & visualization Image Synthesis WS 07/08
Dr. Jens Krger Computer Graphics and Visualization Group Object /
Image Space Stippling black-and-white stippling Supersampling in
screen space surface based anti-aliasing
