Visible Light and X-Ray Ray Tracing of Generalized Cylinders

Abstract

A new algorithm for ray tracing generalized cylinders whose axis is an arbitrary three-dimensional space curve and whose cross-sectional contour can be varied according to a general sweeping rule is presented. The main restriction placed on the class of generalized cylinders that can be ray-traced is that the sweeping rule of the generalized cylinder must be invertible. This algorithm handles a broader class of generalized cylinders than any other reported ray tracer. It has been integrated into a general geometric modeling system that can render objects utilizing visible light as well as simulated X rays. Generalized cylinders are often used in modeling systems because they compactly represent objects. Many commonly occurring objects including snakes, horses, airplanes, flower vases, and organs of the human abdomen such as the stomach and liver can be described naturally and conveniently in terms of one or more generalized cylinder primitives. By extending the class of generalized cylinders that can be conveniently modeled, the presented algorithm enhances the utility of modeling systems based on generalized cylinders. X-ray images of the internal bone structure of a knee joint and a visible light image of a fan blade assembly are presented.