Arc-spline update

The input for the first version of the Arcspline function required the coordinates of the centre of each arc, as well as the angle of the tangents at each end of the arc.  I have now added a new version with simplified input in a 4 column range.

The new file may be downloaded from:

The required inputs are:

  • Row 1: XY coordinates of the start point
  • For each arc: XY  coordinates of the intersection point of the tangents at the ends of the arc, the arc radius, and the number of segments for each arc
  • Last row: XY coordinates of the end point


  • If the spline is a closed curve the end point may be omitted.
  • If the spline is not closed,  set the optional second argument (Closearc) to False.  In this case the end point must be provided.
  • The default return array is the coordinates of the spline curve.  If the third argument (Out) = 1, details of each arc will be returned (see screen shot below for details).

Since the new function input will usually be much more convenient than the original version, it has been named ArcSpline, and the original function has been renamed ArcSpline2.

Input and output for an asymmetric I section with varying radius fillets:

Output with Out = 1:

This entry was posted in Coordinate Geometry, Excel, Maths, Newton, UDFs, VBA and tagged , , , , . Bookmark the permalink.

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