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Show CHAPTER 2 SHADING MODELS: PREVIOUS AND RELATED WORK Sophisticated shading models, coupled carefully with high quality display media, give computer graphics images dramatic vitality. However, the subtle aspects of illumination are not always considered critical to computer graphics applications. It can be difficult to justify computational costs or extensive database development for the generation of high quality images in cases where a shading model that conveys basic shape information is sufficient and much less expensive. Yet computer graphics applications in areas such as architecture, industrial design, or fashion require a sense of the aesthetic qualities of objects, requiring an accurate shading method. What follows is a brief encapsulation of shading models as they have developed in computer graphics. The shading models have become more complex as time has passed, but the focus - balancing computational cost versus shading realism - has not shifted. For the f9llowing description, an effort has been made to use formulas and terms in a consistent framework. All of the shading models in the following discussion can be extended for arbitrary numbers of light sources, but have been described for a single light source for clarity. To simplify the following equations, we define the following function: clamp (x ) = xu_1(x), (2.1) |
