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Aaron Hertzmann New York University
Fast Paint Texture Aaron Hertzmann New York University Pierce Groover CS 395 – NPR Thursday, January 22, 2004
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Overview Texture plays important part in visual appearance
Methods can take a long time Let’s build faster/easy algorithm to work with existing programs and hardware
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Overview
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Other work Simulated buildup of material Fixed texture maps
Cockshott et al. ’92, Curtis et al. 97 Processing time, fluid dynamics Fixed texture maps Bronskill, Litwinowicz, Meier, Markosian No paint mixing or building No consistent lighting on individual strokes
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Implementation - Overview
Raw color image (brush strokes) Height field is computed Height of the painted surface at each pixel Final painting generated by bump-mapping the raw image (Phong shading)
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Brush Strokes Hertzmann and Perlin 2000
Could be any type of stroke though Brush stroke specified by a smooth curve brush radius solid color. texture mapped Brush strokes are tesselated as triangle strips
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Brush Strokes Opacity Map
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Base Image Render a color image
Paint color for each pixel, without lighting Composite every brush stroke in back-to-front order Use opacity map and paint color
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Height Map Per-pixel height of the painted surface.
Initialized to black (zero height) Height determined by texture map, then… First strokes are drawn very dark, later strokes drawn lighter. Boundaries between the two appear as height discontinuities Note that the height map is not cumulative. Adding stroke heights difficult to prevent hidden strokes
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Height Map Height Field Texture Map
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Lighting Bump-map original flat image using directional derivatives from height map Phong shading Done!
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Results
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Results
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Results
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Results
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Future Work New types of stroke textures and new lighting functions
Hardware vertex shaders Paint textures have the shiny, static appearance of viscous oil paint More styles could probably be achieved with suitable stroke textures, height and opacity textures.
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Thank You Questions?
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