| 摘要 |
PURPOSE:To reduce the number of the execution times of commands necessary for the simplification of odd points calculation and for the control of horizontal plotting so as to paint out at high-speed. CONSTITUTION:A circular arc coordinate calculation means 2 calculates a quarter of coordinate on a periphery. An odd points address calculation means 3 is started from the circular arc coordinate calculation means 2 calculates a first address on the frame buffer of the respective points on the circular arc, calculates a second address on the frame buffer of a point which is symmetrical against the respective points on the circular arc with a vertical axis as the axis of symmetry and, furthermore, calculates a third address on the frame buffer of a point which is symmetrical against the respective points on the circular arc with a horizontal axis running the center of the circle as the axis of symmetry. A parallel horizontal drawing means 4 is started from the odd points address calculation means 3 and plots a straight line connecting the first/second addresses and a straight line which sets the third address to be a starting point and which is parallel with the straight line on a frame buffer 5. |
