Greg M. Johnson wrote in message <39D1E46B.CDB2D1A6@my-dejanews.com>...
......
>a,a,b,a  gives very different results from a,b,a,a
>
>Shouldn't any a-b-a be the same?


Not with cubic splines in general, as it requires FOUR control points to
determine the location of any point on the curve.  a-b-a does not give
sufficient information to determine a cubic spline curve.  As to what is
happening to your curve, check the documentation:

*Cubic splines can be calculated in the range between the second and last
but one argument. In the remaining parts linear splines are used.

This means that when you shift the control points, different types of
splines are being used between the same point locations, and thus different
appearances.  Thus you are actually only losing part of your "cubicness"
...the "cubicness" between the second and third points...when you change the
order number on your points (but gaining "cubicness" on the new second and
new third points).  I hope my explanation is clear enough to help......

Quadhall

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