.
Non-Photorealistic Virtual Environments
Allison W. Klein, Wilmot Li, Michael M. Kazhdan, Wagner T. Correa, Adam Finkelstein, Thomas A. Funkhouser.
Proceedings of SIGGRAPH 2000, Kurt Akeley, pp. 527--534, July, ACM Press / ACM SIGGRAPH / Addison Wesley Longman,
2000. [BibTeX]
Texture Mapping for Cel Animation
Author(s): Wagner T. Correa, Robert J. Jensen, Craig E. Thayer, Adam Finkelstein.
Proceedings: Proceedings of SIGGRAPH 98, pp. 435--446, July,
1998.
[BibTeX] 
Abstract:
We present a method for applying complex textures to hand-drawn characters in cel animation. The method correlates features in a simple, textured, 3-D model with features on a hand-drawn figure, and then distorts the model to conform to the hand-drawn artwork. The process uses two new algorithms: a silhouette detection scheme and a depth-preserving warp. The silhouette detection algorithm is simple and efficient, and it produces continuous, smooth, visible contours on a 3-D model. The warp distorts the model in only two dimensions to match the artwork from a given camera perspective, yet preserves 3-D effects such as self-occlusion and foreshortening. The entire process allows animators to combine complex textures with hand-drawn artwork, leveraging the strengths of 3-D computer graphics while retaining the expressiveness of traditional handdrawn cel animation.