抄録
The authors have been developing KETpic as a bundle of macro packages for Computer Algebra Systems (CASs) to draw fine TEX-pictures. Recently we have developed a new method of the surface drawing using KETpic. We have obtained the equation to characterize the points on the ridgelines of surface. Also the technique of hidden line elimination has been used. Since the graphics drawn by using KETpic are monochrome and are composed of lines, they must be useful when they are used in the mass printed teaching materials.
