2369	 Hidden Lines Elimination for a Rotating Object	 A method is presented of determining which parts of three-dimensional objects are visible and which are invisible when the objects are rotated about some axis. This paper describes a polygon comparison scheme in which the relationships of two polygons can be classified into tree types and also discusses how the relationship is changed for each pair of polygons under rotation about some axis. A rotation table is defined for each pair of polygons which remains fixed as long as rotation is about one axis and provides a means of rapidly determining the visible and hidden line relationship between two polygons. Additional work must be done to extend this approach to simultaneous rotation about several axes. hidden line problem display programming computer graphics displays graphics computer drawn picture
