Posted on

The Right CAD Curve

The Right CAD Curve

Bezier Curves, Not Splines, Are Truly Smooth Curves

by David Golber

Originally published in American Lutherie #72, 2002 and Big Red Book of American Lutherie Volume Six, 2013

Bezier curves, as opposed to splines, have been known since the 1970s. They are supported by AutoCAD and AutoCAD LT, but not by many other popular CAD packages. What are they, and why do we care?

It’s easiest to start with an example. Fig. 1 shows the outline of a harpsichord. Look at the curved side. The coordinates of the points are from Kielklaviere,1 which describes the curved side of the instrument by listing the coordinates of points along the side. The curve in Fig. 1 is the ordinary spline through those points. Fig. 2 shows that one of the points is erroneous enough that it clearly makes the curve bumpy.

Become A Member to Continue Reading This Article

This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

If you are already a member, login for access or contact us to setup your account.