1. Aaron Hertzmann New York University
Fast Paint Texture
Aaron Hertzmann
New York University
Pierce Groover
CS 395 – NPR
Thursday, January 22, 2004

2. 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

3. Overview

4. 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

5. 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)

6. 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

7. Brush Strokes
Opacity Map

8. 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

9. 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

10. Height Map
Height Field
Texture Map

11. Lighting
Bump-map original flat image using directional derivatives from height map
Phong shading
Done!

12. Results

13. Results

14. Results

15. Results

16. 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.

17. Thank You
Questions?