Interactive Non-Photorealistic Technical Illustration
Author(s): Amy A. Gooch.
Master Thesis: Department of Computer Science, University of Utah, December,
1998.
[BibTeX] 
Abstract:
Current interactive modeling systems allow users to view models in wireframe or Phong-shaded images. However, the wireframe is based on the model's parameterization, and a model's features may get lost in a nest of lines. Alone, a fully rendered image may not provide enough useful information about the structure or model features. Human technical illustrators follow certain visual conventions that are unlike Phong-shaded or wireframe renderings, and the drawings they produce are subjectively superior to conventional computer renderings. This thesis explores lighting, shading, and line illustration conventions used by technical illustrators. These conventions are implemented in a modeling system to create a new method of displaying and viewing complex NURBS models. In particular, silhouettes and edge lines are drawn in a manner similar to pen-and-ink drawings, and a shading algorithm is used that is similar to ink-wash or air-brush renderings for areas inside the silhouettes. This shading has a low intensity variation so that the black silhouettes remain visually distinct, and it has a cool-to-warm hue transition to help accent surface orientation. Applying these illustration methods produces images that are closer to human-drawn illustrations than is provided by traditional computer graphics approaches.