A Raster scan visibility algorithm for parametric surfaces

Abstract

A raster scan visibility algorithm is presented for contouring on parametric surfaces. The algorithm entails three-dimensional aspects of coloring, shading, and visibility of points. The approach uses parametric interpolation functions as the primary basis in computations. This technique along with a predictor-corrector method makes contour line tracing on each element more accurate. Continuous color variations on each surface are produced through the use of interpolation functions. The color at every display point can be assigned in proportion to the value of the quantity of interest at that pixel. Shading is included involving several possibilities of the shading rule. They may include ambient light, diffuse reflection, specular reflection, shadows, or transparency. A combination of these may also be included. All of the graphics generated using this algorithm can be displayed on color graphics, as well as, non-color graphics display terminals, and line printers. The algorithm could be used as a segment of a complete computer graphics package.