How to complete the following model?

Hi guys,
I want to create the following shape, something like a tap. Can you please show me the procedure step by step?
1.3dm (42.6 KB)

first clean the curves up, you have one tiny kinky extra curve. then join them that you have 4 arms. splitting them at exactly one spot. i would strongly suggest you work those curves further, you curvature is a real mess, also the curves do not hit the tangency of the cylinder.

anyway after that call up NetworkSrf and select those 4 curves plus the upper boundary of the cylinder you may need higher amount of interior curves for this to work nicely, after you cleaned up the kinks at the tip otherwise this will not work precise.

another option would be to split the cylinder boundary also in 4 curves and use sweep 2 then match them together

Hej Alex,

you can take half a sphere and simply transform its control points until you’re happy. This way, you also don’t have curvature continuity issues. It’s a single surface.

Horn.3dm (37.6 KB)


or use two rails and one profile with sweep2 to get somewhere close
then remove a few knots and tinker with the CV`s

I can’t understand what conditions are necessary for matching degree 2-9 point surfaces. Sometimes I get a clean match most times the matching surface becomes a polysurface. That’s without ticking the refine match option.

It is the fully-multiple knots that are causing matchsrf to break it up into multiple joined surfaces instead of a single surface. MatchSrf has always messed up with surfaces with fully multiple knots. If you are going to make surfaces with fully-multiple knots you will have to do the matching manually.

Here is one way using loose loft 1x.3dm (97.8 KB)

where did you catch all those fancy words? i had to google this up, though i knew its some kind of multi knot but thought at first this is a typo fully multiple knot. i would have thought RemoveMultiKnot would do this, but deleting the knots manually with RemoveKnot works.

i would recommend to use Rebuild if you dont want to loft it with new profiles.

RemoveMultiKnot specifically avoids fully (i.e. degree number of knots, = kinks) multiple knots.


Thanks. It just seems odd that I can use “merge smooth no” to get it back to a single surface.

@pascal I also assumed RemoveMultiKnot was designed to remove stacked surface knots. But just didn’t work.

Yes, you can do that, but it may not be a good idea. I think you will find the surface now has internal discontinuities that might cause future problems.
If you try offsetting the surface before merging, I think you will find the seams pulling apart on the offset surfaces.