Here is the Savitzky–Golay filter method that might help. (?)
"The method has been extended for the treatment of 2- and 3-dimensional data."

https://en.wikipedia.org/wiki/Savitzky%E2%80%93Golay_filter

The math looks tough, but might be comprehensible with much study.
3rd and 4th derivatives?
Looks like javascript would not be adequate for 3D. (?)
There are two Convolution Coefficient Calculator software packages available for free download.
No Idea how NURBS formulas would apply.

Found all kinds of weird names and topics with a search of Smoothing Curves.

- Brian

The other day, read article about why windshields have those dot/shading patterns, near edges.