non-photorealistic rendering
DESCRIPTION
Non-Photorealistic Rendering. Greg Turk College of Computing and GVU Center. Painterly Rendering for Animation Barbara Meier, SIGGRAPH 1996. Painterly Rendering Issues. Frame-to-frame coherence (maintain strokes across time) Idea: fix brush strokes in screen-space - PowerPoint PPT PresentationTRANSCRIPT
Non-PhotorealisticRendering
Greg TurkCollege of Computing and GVU Center
Painterly Rendering for Animation Barbara Meier, SIGGRAPH 1996
Painterly Rendering Issues
• Frame-to-frame coherence (maintain strokes across time)
• Idea: fix brush strokes in screen-space
• Problem: shower door effect
• Better idea: fix brush strokes to object
Painting Pipeline
Brushes (color & opacity):
Different Brushes and Orientation Fields
Draw Image in Layers
Video
Pen and Ink SketchesMike Salisbury, Michael Wong, John Hughesand David Salesin, SIGGRAPH 1997
Pen and Ink
• Given: grayscale image (e.g. photo)
• Make: pen-and-ink illustration
• Approach:
Gray scaleimage
Directionfield
BrushStrokes
FinalImage+ + =
Pen and Ink Sketches
ToneMap
OrientationField
Strokes
Pen and Ink Sketches
ToneMap
OrientationField
Strokes
Stroke Details
• Strokes are B-spline curves (similar to Bezier)
• Strokes clipped to silhouettes
• Stroke density controlled by blurred stroke image
• Strokes follow orientation field
Painting Orientation Field
Stroke Density
Strokes
BlurredStrokes
Stroke Density Varies with Drawing Size
Art-Based RenderingOf Fur, Grass andTrees
Kowalski, Markosian,Northrup, Bourdev,Barzel and Hughes,SIGGRAPH 2000
Approach
• Real-time rendering
• Use reference images for color and object ID
• Place “strokes” based on density
• Try to place same strokes on next frame
Reference Images: Hardware Rendering
Final Image
Stroke Drawing
“Illustrating Smooth Surfaces”Aaron Hertzmanand Denis ZorinSIGGRAPH 2000
Goals
• Create pen-and-ink strokes based on 3D geometry
• Show silhouettes
• Have cross-hatching
Issues
• Silhouette detection
• Orientation field (use curvature)
• Hatching
• Undercuts
Silhouette Detection
Orientation Field Smoothing
Orientation Field and Shading
Hatching
Hatching and Undercuts
Results
Results
Other NPR
• Cel Animation
• Painterly Video
• Cel Video
• ???
Painterly Video
“What Dreams May Come”
Cel Animation: Zelda Windwalker
Cel-Like Video
End