Visible Light and X-Ray Ray Tracing of Generalized Cylinders

A new algorithm for ray tracing generalized cylinders whose axis is an arbit:rary three dimensional space curve and whose cross-sectional contour can be varied accortding to a general sweeping rule is presented. The only 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 ainy other reported ray tracer. It has been integrated into a general geometric modeling systenn that can render objects utilizing visible light as well as simulated X-rays. Generalized cylinders are often used in modeling systems because they cornpactly represent objects. Many commonly occurring objects including snakes, horses, airplanes, flower vases, and organ,s 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. Index Terms : computer-generated images; generalized cylinder; ray tracing; simulated X-ray images; radiograph;