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Method of Determining the Octant of a Point on an Ellipse

IP.com Disclosure Number: IPCOM000060515D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08

Publishing Venue

IBM

Related People

Authors:
Makowka, CD [+details]

Abstract

A technique is described whereby one point on an ellipse is determined to be in an octant based on the slope of the tangent to the ellipse at that point. The octants are defined by an analogy to a circle. In the utilization of a computer graphics display raster or the printer output from a computer, techniques of representing an ellipse or a circle require knowledge of the octant of a beginning or an ending point on the ellipse. The octants for a circle would be numbered as shown in the drawing. Using the same analogy, the octants for the ellipse are similarly defined, such that the range of slopes for the tangents correspond to similar tangents of the same range of slopes for the circle.