Non-Photorealistic Computer Graphics Library

Real-Time Hatching

Author(s): Emil Praun, Hugues Hoppe, Matthew Webb, Adam Finkelstein.
Proceedings: SIGGRAPH 2001, 2001.
[BibTeX]

Abstract:
Drawing surfaces using hatching strokes simultaneously conveys material, tone, and form. We present a system for real-time rendering of hatching strokes over arbitrary surfaces, in a variety of non-photorealistic styles. During an automatic preprocess, we construct a sequence of mip-mapped hatch images corresponding to different tones, collectively called a tonal art map. Strokes within the hatch images are scaled to attain appropriate stroke size and density at all resolutions, and are organized to maintain coherence across scales and tones. At runtime, hardware multitexturing blends the hatch images over the rendered faces to locally vary tone while maintaining both spatial and temporal coherence. In order to render strokes over arbitrary surfaces, we build a lapped texture parametrization where the overlapping patches align to a curvaturebased direction field. By exploiting modern texture-mapping hardware, our scheme convincingly renders hatching strokes in real-time on a variety of complex surfaces.