公开(公告)号：CA1309523C

公开(公告)日：1992-10-27

申请号：CA565450

申请日：1988-04-29

Applicant: IBM

Inventor： CLARK DAVID A ,  FARR ROBERT W E

IPC: G06T11/00 ,  G06T11/20 ,  G09G1/08 ,  G09G5/20 ,  G09G1/14

Abstract: UK9-85-011 CURVE GENERATION IN A DISPLAY SYSTEM A curve generator for a display system comprises arc generation means for generating an arc of a circle from data defining the locations of two end points and an intermediate point on the arc. The arc generation means comprises initialisation means for calculating the angle subtended between a first vector, from a first of the end points to the intermediate point and a second vector from the second of the end points to the intermediate point and arc plotting means for defining a succession of further vectors from said first end point and for calculating, for each further vector, its point of intersection with a counterpart vector, from the second end point, with which it subtends said angle, whereby a succession of further points are plotted on the circular arc. The plotting logic thus plots the points of the arc with respect to a given point on the arc itself by generating vectors from that given point and enables the computation of the arc to be performed substantially within the system co-ordinate space in which the arc exists, which reduces the number of places of accuracy needed in order to accurately compute the arc.