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See also: About B Splines
Creates a bi-cubic spline curve entity.
A B Spline curve needs a set of control points, but does not necessarily pass through the points. However, it always passes through the first and last points.
B Splines are used for general curves where any abrupt changes of the control points will be smoothed.
At the start, the curve is tangential to a line between the first two control points and at its end is tangential to a line between the last two control points. If a single control point is moved, it only changes the curve in that locality - other regions of the curve are unaffected.
A feature of the B Spline is the 'degree' of the curve. The degree is specified as an integer between 1 and 10. Generally, the lower the degree, the closer the curve will follow the track lines (straight lines between the control points). A degree of 1 produces the track lines themselves. The higher the degree, the flatter the curve. A degree of between 2 and 5 is the most useful in practice, and the default value is 3.
Repeating a control point influences the curve by pulling it sharply towards that point while not reducing its (mathematical) smoothness. The shape of a curve may also be influenced by introducing a different weighting factor for each control point. Such a curve is called a rational B Spline. A curve created with EdgeCAM has a weighting of 1.0 assigned to each point and is therefore non-rational.
Tolerance - Specifies a value that alters the displayed smoothness of the curve. The smaller the tolerance value, the smoother the curve. Note that this is a display function only and does not alter the mathematically correct shape of the curve.
Degree - Specifies a control factor for the b-spline curve, usually 3. Degree can vary from 1-10 but must be less than the number of control points. High values create flatter curves but take longer.
Name - Specifies a name for the b-spline curve entity. Use this name later to select the entity.