ToNurbs - Starpoint-Repair

After SubD → ToNurbs Starpoints and N-Gons might not have satisfying quality.
As mentioned several times, a nice typology might help / improve the results.

But did someone establish a nice technique to “repair” the starpoints in the resulting Polysurface ?

There is already a lot of details / background info in this topic:

@gustojunk is showing some nice sphere trim + (x-nurbs) patch to replace some critical areas.
did you make any progress to automate this in Grasshopper ?

@spb mentions a similar approach for fillets “atomic bomb” here.

My approach today was to do a 4-side trim and insert a single span Degree 5,5 Surface.
followed with multiple sequences of _matchSrf and manual _insertKnot
for the trim i skipped the moste acute / pointed angle Face.
I am not super happy with the result - but maybe a startingpoint ?

any ideas of how to improve Starpoints after ToNurbs ?
(and maybe we’ll get a command for this ?)

starpoint_repair.3dm (153.0 KB)

kind regards -tom

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that was a crazy idea I had at that time, but it was too hacky. Our workflow now is a bit more complex but more reliable: we do all our conversions in either one PC still running Rhino 5 and Tsplines, or in Fusion 360. The quality is good enough to make tootable parts.


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there is this old topic about matching

did you ever get an answer on this ?

there also seam to be some scientific stuff - just as an entripoint:
Towards untrimmed NURBS: CAD embedded reparameterization of trimmed B-rep geometry using frame-field guided global parameterization

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