Rapid raster ellipsoid shading
Don Herbison-Evans · ACM SIGGRAPH Computer Graphics · 1980
The problems of coloring figures composed of 3-dimensional ellipsoids are discussed.The problem of identifying the ellipsoid that colors a particular pixel is considered First.The use of osculating rectangular boxes and spheres to reduce the number of quadratic equations that have to be solved are described, and their limitations evaluated.In the calculation of the color of a pixel, the u~e of the y (vertical) rather than z (longitudinal) component of the surface normal• is advocated as giving more natural pictures despite the absence of shadows° The use of moduli rather than squared components speeds the calculation and gives pictures that are perfectly acceptable.This is illustrated.