Computer Graphics Using Raytracing

Abstract

In the field of computer graphics, almost any technique for generating an output image can be viewed as a data transformation. The output image is a function of some input data set and the rendering algorithms used to generate that image are mapping functions. The source of the data set may be explicit, such as models and structures produced by an artist or designer, or be implicit, such as the result of a physical simulation or the surface of a fractal. There are many methods for transforming the input visual scene description into the target image. Rasterization, the process of converting an image described in vector for into a raster image [Foley 90] is a popular technique, particularly useful in modern, hardware accelerated systems. However, it tends to break down, losing its efficiency and attractiveness when scene complexity increases and geometric primitives shrink in size. Furthermore, since rasterization methods are often tuned to render simple geometry such as triangles, direct rasterization of implicit surfaces such as quadrics is not straight forward. In offline systems, a commonly used algorithm for the rendering of very fine geometry and implicit surfaces is the Reyes algorithm [Cook 87]. The Reyes algorithm, developed in the mid 1980s by a group that was to become Pixar, renders implicit geometry and smooth surfaces by recursively subdividing it into polygons until each facet becomes smaller than a single pixel. Each polygon is then rendered as a flat, single colored primitive.