Mystery - Why does Join give an Open Curve?


Join Fail.3dm (47.9 KB)

Can anyone work out why these curves join to give an open curve rather than a closed curve?

It joins into a closed curve here in Rhino 8 BETA.

1 Like

Thanks Martin, that is encouraging I’m running Rhino 7SR35 - anyone know what is going on there? does it fail in other Rhino 7’s?

This is an odd one. If you select all and join, it makes a bad object. However if you select some different subsets of the curves and join in several steps it sometimes makes a good closed object, and sometimes not. If you take the first bad object and explode and rejoin, it becomes a good, closed curve. There is some sort of weird tolerance thing going on.

Yes, V8 seems to have fixed that particular problem.

there is a small curve here

that is probably causing the issues. If you join that first to its neighbors, then join there rest to it, you get a closed curve.
I suspect this has been fixed in V8 by a tune-up that @chuck made to an issue found in CurveBoolean

1 Like

Good catch, I did a SelShortCrv with the 0.01 file tolerance and didn’t find anything… because that curve is 0.015 long. Though not necessarily good practice, in theory, that should still be acceptable.

Thank you @Gijs & @Helvetosaur It is good to understand what is going on here :slight_smile:

Is there any likelyhood of the tune up reach Rhino 7?

This geometry comes from one of our CNC customers (not sure how they generated it).

not very likely, no