[1] [2] 
Real-Time Nonphotorealistic Rendering
Author(s): Lee Markosian, Michael A. Kowalski, Samuel J. Trychin, Lubomir D. Bourdev, Daniel Goldstein, John F. Hughes.
Proceedings: ACM Siggraph 97, Annual Conference Series 1997, pp. 415--420, August,
1997.
[BibTeX] 
Abstract:
Nonphotorealistic rendering (NPR) can help make comprehensible but simple pictures of complicated objects by employing an economy of line. But current nonphotorealistic rendering is primarily a batch process. This paper presents a real-time nonphotorealistic renderer that deliberately trades accuracy and detail for speed. Our renderer uses a method for determining visible lines and surfaces which is a modification of Appel’s hidden-line algorithm, with improvements which are based on the topology of singular maps of
a surface into the plane. The method we describe for determining visibility has the potential to be used in any NPR system that requires a description of visible lines or surfaces in the scene. The major contribution of this paper is thus to describe a tool which can significantly improve the performance of these systems. We demonstrate the systemwith several nonphotorealistic rendering styles, all of which operate on complex models at interactive frame rates.
Statistical Techniques for the Automatic Generation of Non-Photorealistic Images
S. M. F. Treavett, Min Chen.
Proc. 15th Eurographics UK Conference, March,
1997. [BibTeX]