We present a system that lets a designer directly annotate a 3D model with strokes, imparting a personal aesthetic to the non-photorealistic rendering of the object. The artist chooses a "brush" style, then draws strokes over the model from one or more viewpoints. When the system renders the scene from any new viewpoint, it adapts the number and placement of the strokes appropriately to maintain the original look.

We apply simple techniques from traditional artistic composition to the art-based rendering of interactive 3D scenes. A human scene-modeler makes choices about composition in a scene and our sys-tem dynamically adjusts the rendering attributes of objects in the scene to achieve the desired effects for a given view. We can selec-tively group scene elements through shared tone, color, and outline, so as to simplify and structure an image. This can be used, together with controlled level of detail, to emphasize important objects. Fi-nally, we show a technique for adaptively changing color or other attributes to control the contrast of adjacent elements in the pic-ture. We also briefly discuss ideas about larger-scale compositional issues.

Artists and illustrators can evoke the complexity of fur or vegetation with relatively few well-placed strokes. We present an algorithm that uses strokes to render 3D computer graphics scenes in a stylized manner suggesting the complexity of the scene without representing it explicitly. The basic algorithm is customizable to produce a range of effects including fur, grass and trees, as we demonstrate in this paper and accompanying video. The algorithm is implemented within a broader framework that supports procedural stroke-based textures on polyhedral models. It renders moderately complex scenes at multiple frames per second on current graphics workstations, and provides some interframe coherence. CR Categories and Subject Descriptors: I.3.3: Computer Graphics: Picture/Image Generation; line and curve generation; bitmap and frambuffer operations; I.3.5 Computer Graphics: Computational Geometry and Object Modeling: curve, surface, solid, and object representations; I.3.7: Three-Dimens...

Nonphotorealistic rendering (NPR) can help make comprehensible but simple pictures of complicated objects by employing an econ-omy 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 im-provements 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 re-quires 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 demon-strate the system with several nonphotorealistic rendering styles, all of which operate on complex models at interactive frame rates.