Remove knot from NURBS curve or Surface, like command "RemoveKnot" or "RemoveMultiKnot"

I am doing geometry modification of a wind turbine, it has too many control points in the loft surfaces. If I use rebuild, it will directly change the geometry of the leading edge which has high curvature. So could I use any library to remove knot of NURBS curve or surface before or after I loft curves in grasshopper? I couldn't find it in Rhinocommon library.

By the way, I get help from insert knot in "http://www.grasshopper3d.com/forum/topics/list-and-insertknot-in-grasshopper?commentId=2985220%3AComment%3A1106674&xg_source=activity". So is here any similar function for knot removing?

Replies to This Discussion

Permalink Reply by Stephen Maher on October 19, 2014 at 10:06pm

According to this post on the Rhino.Python Programmer's Reference site, [RemoveSurfaceKnot] is not a command in rhinoscriptsyntax yet.

I suggest rebuilding the curve prior to lofting. You can use the [RemoveCurveKnot] command in the rhinoscriptsyntax library or simply rebuild the curve in Grasshopper.

This is a fairly broad answer. If you post the file and/or an image of the geometry, I (or someone else) might be able to address your specific needs.

Cheers,

/SPM

Permalink Reply by Austin Herrema on October 23, 2014 at 11:58am

Hi Stephen,

Thanks for your reply. I'm working with Chenglong on this project and can provide some imagery to better describe our problem. We have a set of airfoil profiles that are defined by a large number (about 400) control points (getting an accurate curvature is very important). These profiles, with accompanying control points, can be seen below:

We have experimented with rebuilding these curves, as shown below:

However, such a rebuild too greatly changes the profile in areas of high curvature. Thus, we would like to be able to remove the knots (in GH, not afterwards in Rhino) around the part of the profile that has low curvature (i.e. the top and bottom segments), whilst leaving the knots at the front unchanged (or only very slightly reduced).

Ultimately, we are lofting these profiles so any solution that would achieve this kind of focused resolution either pre- or post-loft would be acceptable. Any help and/or suggestions you (or someone else!) can provide would be great.

Thank you!

Austin

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