GRAPHIC METHOD AND APPARATUS FOR DRAWING CLOSED QUADRATIC CURVE POINT TO POINT BASIS

摘要

PURPOSE: To draw a completely closed quadratic curve with a continuous shifting single cursor by plotting a circle by a mode advancing continuously from an octant to a next octant and returning to the original place again. CONSTITUTION: The arc of a curve is drawn by repeating point-to-point correspondence plotting in a first octant by using the reference of a relative coordinate. Further, as the origin of the curve drawn in a second octant, the last point drawn in the first octant is adopted. The new U and V references of relative coordinate of the second octant as the function of the tangent drawn on the curve at this new origin and the direction of the displacement on the curve. By including the value of the last point drawn in the first octant in a register, the initial value related to this new U and Y reference for the picture in this second octant is calculated. The arc of the curve in the second octant is drawn by repeating point-to-point correspondence plotting by using the new reference of the relative coordinate. The work determining the reference of the relative coordinate and drawing in all the octants covered by the arc of the curve is restarted.