Draft CubicBezCurve

Description
The CubicBezCurve tool creates a Bezier Curve of third degree. This is one of the most commonly used Bezier curves. This tool allows you to create a big spline made of several 3rd-degree Bezier segments, in a way that is similar to the Bezier tool in Inkscape. A Bezier curve of any degree can be created with Draft BezCurve.

The Draft BezCurve and the Draft CubicBezCurve tools use to define the direction of the curve; on the other hand the Draft BSpline tool specifies the exact points through which the curve will go.



How to use

 * 1) Press the  button.
 * 2) Click a first point on the 3D view, and hold the mouse pointer.
 * 3) Drag the pointer to another point on the 3D view, and release the pointer.
 * 4) Move the pointer to another point on the 3D view to adjust the curvature of the spline, and click and hold on the point.
 * 5) Move the pointer to another point on the 3D view to adjust the final curvature of the spline, and then release the pointer. This creates a Bezier curve of 3rd degree, and continues drawing from the last point.
 * 6) Repeat the process of clicking, holding, dragging, and releasing to add points, and create further 3rd-degree Bezier segments.
 * 7) Press  or the  button, to complete the edition.

Scripting
Draft API and FreeCAD Scripting Basics.

See Draft BezCurve for the general information information. A cubic Bezier is created by passing the option  to.

For each cubic Bezier segment four points must be used, of which the two intermediate points are the control points.
 * If only 3 points are given, it creates a quadratic Bezier instead.
 * If only 2 points are given, it creates a linear Bezier, that is, a straight line.
 * If 5 points are given, the first 4 create a cubic Bezier segment; the fourth and the fifth points are used to create a straight line.
 * If 6 points are given, the first 4 create a cubic Bezier segment; the fourth and the other two points are used to create a quadratic Bezier segment.
 * If 7 points are given, the first 4 create a cubic Bezier segment; the fourth and the other three are used to create a second cubic Bezier segment.
 * That is, whenever possible, the last point in a cubic Bezier is shared withe following points.

Example: