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 present a technique for rendering animations in a painterly style.The difficulty in using existing still frame methods for animation is getting the paint to "stick" to surfaces rather than randomly change with each frame, while still retaining a hand-crafted look.We extend the still frame method to animation by solving two major specific problems of previous techniques.First our method eliminates the "shower door" effect in which an animation appears as if it were being viewed through textured glass because brush strokes stick to the viewplane not to the animating surfaces.Second, our technique provides for frame-to-frame coherence in animations so that the resulting frames do not randomly change every frame.To maintain coherence, we model surfaces as 3d particle sets which are rendered as 2d paint brush strokes in screen space much like an artist lays down brush strokes on a canvas.We use geometric and lighting properties of the surfaces to control the appearance of brush strokes.This powerful combination of using 3d particles, surface lighting information, and rendering 2d brush strokes in screen space gives us the painterly style we desire and forces the brush strokes to stick to animating surfaces.By varying lighting and choosing brush stroke parameters we can create many varied painterly styles.We illustrate the method with images and animated sequences and present specific technical and creative suggestions for achieving different looks.

Color is used in computer graphics to code information, to call attention to items, to signal a user, and to enhance display aesthetics, but using color effectively and tastefully is often beyond the abilities of application programmers because the study of color crosses many disciplines, and many aspects, such as human color vision, are not completely understood. We compiled a comprehensive set of guidelines for the proper use of color, but even these guidelines cannot provide all of the aesthetic and human factors knowledge necessary for making good color selections. Furthermore, programmers may misinterpret or ignore the guidelines. To alleviate some of these problems, we have implemented ACE, A Color Expert system which embodies the color rules and applies them to user interface design. The goal of the implementation was to test whether an automated mechanism would be a viable solution to the problem of choosing effective and tasteful colors.Our implementation is written in OPS5, a production system programming language, which allowed us encode rules in a similar fashion to our existing set of guidelines. ACE takes a user interface specification and uses our color rules as constraints to determine the best colors for particular items. While ACE is only a prototype, we learned that an expert system is a viable method for choosing an initial set of colors that can be “tweaked” by a human expert. We also learned that much more research needs to be performed in the areas of visual color relationships and how they can be used to provide the most effective user interface.