Nonphotorealistic Rendering

Computer graphics is concerned with the production of images in order to convey visual information. Historically, research in computer graphics has focused primarily on the problem of producing images which are indistinguishable from photographs. But graphic designers have long understood that photographs are not always the best choice for presenting visual information. A growing body of research in computer graphics has addressed the problem of producing nonphotorealistic imagery, but usually at the expense of long rendering times (e.g., [MEIE96][WINK96]). Recent work by the Center has achieved attractive nonphotorealistic imagery at interactive frame rates [MARK97].

Over the next few years we will develop improved algorithms for producing non-photorealistic renderings at interactive rates. Our goals are to support a broader range of rendering styles (going beyond simple line drawings) and to develop more general methods for maintain ing both frame-to-frame coherence and a given level of detail of imagery in screen space. To exploit more interesting possibilities of nonphotorealistic rendering, such as rendering complex organic forms (e.g., plants or fur), we will develop techniques for defining higher-level "procedural textures." These will be distinguished from conventional procedural textures (e.g., shaders in Pixar's Renderman) in that they will not operate on a per-pixel basis. Rather, they will build pictures out of higher-level picture elements such as hash marks and brush strokes. Key challenges are to control qualities of the final image such as tone and level-of-detail in real-time.

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[MARK97] L. Markosian, M.A. Kowalski, S.J. Trychin, L.D. Bourdev, D. Goldstein, J.F. Hughes. Real-Time Nonphotorealistic Rendering, To appear in proceedings of SIGGRAPH '97, August 1997.

[MEIE96] B. Meier. Painterly Rendering for Animation. In proceedings of SIGGRAPH '96, pp. 477-484, August 1996.

[WINK96] G. Winkenbach and D. Salesin. Rendering parametric surfaces in pen and ink. In proceedings of SIGGRAPH '96, pp. 469-476, August 1996.