| 摘要 |
PURPOSE:To quickly perform the approximating calculation of an ellipse by approximate representation of the ellipse in terms of two kinds of arc whose points of contact are intersections of tangents of the ellipse. CONSTITUTION:Data of two points on the major axis of the ellipse is given to a coordinate parameter operating part 1 and is held in a coordinate parameter register part 2 as a fundamental item required for final operation. The axis ration of the ellipse is given to a ratio parameter operating part 3 and is held in a ratio parameter register part 4. A mixture operating part 5 obtains center points of four pairs of arcs approximately expressing the ellipse and holds them in an output data register part 6. A CRT controller 8 calculates point strings of pertinent arcs and sends them to a display part 9 to display them. That is, center points of four pairs of arcs approximating the ellipse and start and end point data of arcs are converted to four commands by a command converting part 7 and are sent to the display part 9 to display them. |
