System and method for specifying elliptical parameters

摘要

An interactive elliptical arc control system and method are disclosed. Three control points are provided-a center control point and two foci control points-that a user can interactively manipulate in order to specify and change the elliptical parameters involved. The center control point can control the radius of the ellipse in the x direction, while keeping constant the ratio of the radius of the ellipse in the y direction to the radius of the ellipse in the x direction. The center control point can also control the relationship of the sweep flag to the large arc flag involved. The two foci control points can control the ratio of the radius of the ellipse in the y direction to the radius of the ellipse in the x direction, the angle from the x-axis of the coordinate system to the x-axis of the ellipse, and the value of the sweep flag.