Creating parametric curves

Press the curve tool button in order to create parametric curves, which are defined by three or more control points. The menu appears at the right end of the menu bar. The menu items, as shown below, consist of options to select the type of the curve, i.e., cubic spline, B-spline, Bezier, parabola and polyline. The . marked option is used for creation of parametric curves. The option can be changed by selecting the menu item before or while control points being entered. The shape of the curve is formed as the control points are consecutively entered. There is no limit to the number of control points on a curve. In order to terminate entering the control points and complete a curve, click the last control point once again, or press key (Windows : key).

> Cubic Spline

While this option is checked, a cubic spline curve is created by entering four or more points. When the first and the second point are entered, a straight line is drawn, connecting these two points. The third point makes a parabola. A cubic spline curve is formed after the fourth and the consecutive points are entered. The shape of the curve is continuously varied as the control points are added, and finalized only when the last control point is entered.

< Progress of creating cubic spline >

> B-Spline

While this option is checked, a B-spline curve is created by entering three or more control points. When the first and the second point are entered, a straight line is drawn, connecting these two points. A B-spline curve is formed when the third and the consecutive points are entered. The process of creating B-spline curves is similar to that of creating cubic spline curves. A closed B-spline curve is obtained by overlapping the last control point over the first one.

> Bezier

While this option is checked, a Bezier curve is created by entering three or more c o n t rol points. A Bezier curve is formed when the third and the consecutive points are entered. The process of creating Bezier curves is similar to that of creating cubic spline curves.

> Polynomial

While this option is checked, a polynomial curve is created by entering three or more control points. A polynomial curve represented by Laplacian parameters is formed when the third and the consecutive points are entered.

> Polyline

While this option is checked, a polyline is created by entering three or more control points. A polyline is represented by line segments connecting consecutive two points. A polygon is obtained by overlapping the last control point over the first one.

< Parametric curves >