Trim wrong and strange

See attached.
Trim fail.3dm (45.0 KB)

I want to trim the inside of the ring by the 2 lines.
While the command runs:
Where do the edges in the preview come from?

Final result:
Not ok.
A detail:

The trim works ok when I extrude the 2 lines first.

Hi Charles - as is the object has large edge tolerances (_What command) - how was the existing trim on the surface created? If you untrim this, your new trim works as expected (here).


Tried and seems the trim fails if the trim lines are not joined.
Joined ones work ok.

Hi Pascal:
The srf was made by Sweep1 a profile.
It has the large tolerance because Rhino decided to make it so.
Now I see it as well:

You are right, with the joined lines, it works.
I wonder why I didn’t try this.
Thank you.

As Rhino knows both trim objects, regardless if joined or not, shouldn’t it do the same in both cases?

It should work in both cases. or Trim command should give error that forces user to use joined curves.

Hi Charles - the surface is OK, but there’s a trim in it as the file opens my question was about this trim - I could not reproduce the high edge tolerance here, starting from an untrimmed version of the surface and trimming again, so I was curious to know what the trimming object was for that initial trim- (seems to be the source of the out-of-tolerance…)


Hi Pascal

I’m not aware of an initial trim.
‘Of course’ I can’t retrace the exact situation.

As said, the srf was made with V6 Sweep1, but when I try this now, it is in tolerance.

See attached.
InitialA.3dm (35.3 KB)

This is what I initially have.
Perhaps you can show a way how to model this in a non-cumbersome way without 156 steps to go?

Thank you

Hi Charles, - all I am saying is that as the file opens the object is already trimmed at least once:

This trim appears to have cause the out of tolerance edges, I’m just wondering if the trimming objects for that trim are available - I completely understand if they are not, but if they are, I’d like to have them so that I could reproduce the whole mess from scratch, which might help troubleshooting.