‘Spline interpolation using not-a-knot end conditions. The interpolated value at a query point is based on a cubic interpolation of the values at neighboring grid points in each respective dimension.’
It does not appear to be the same as 'cubic'. According to the documentation, 'cubic' is currently the same as 'pchip'.
there are functions provided to export your surface to IGES. I don't think that you will need to change the order or the degree of the surface, and remember that a Bezier surface is a B-spline surface with knot vectors [0,...0,1,...,1] in the two parametric directions.
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