I wrote:
> Due to the maths involved, there is no known way to calculate the exact
> length of a cubic spline.  The best method is usually to sum the linear
> distances between a number of steps along the spline - obviously, the more
> steps, the more accurate the result (at the cost of speed)...

Fabian BRAU <Fab### [at] umhacbe> wrote:
> If you know the exact form of the function (the spline) you
> can calculate the length of the spline, this involve a simple integrale.
> Actually this is what you do approximately by using straight line
> between point.

Yes, it seems obvious that you could integrate the spline function to find
the exact length.  But like I said, there is simply no known way *to*
integrate the function.  To create my Spline Macro File I searched and
re-searched the web for the right formulas, and also started from first
principals to derive the functions myself, before attempting (without
success) the necessary integration in MathCAD.  I guess it shows that there
are limits to our knowledge of mathematics....

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