Hi Igor - to do that, first select your object and run Edit/Separate on it to break it into individual surfaces.

That is necessary because to remove a trimming boundary any edge of the boundary cannnot be a joined edge between 2 different surfaces, which is what you will have in that case with the upper and lower caps part joined to the cylinder part.

Once you have the cylinder part as an individual object, select one of its edges, then do Ctrl+A to select all edges, then hit Delete. That will remove the boundary and erase the hole like you want.

If you still can't get that to work, could you please post the 3DM model file so I can take a look at it?

Basically, when you have a hole that crosses a seam like that, the seam is actually part of the outer trimming boundary. For example with a surface like this:




If you could look at the entire outer trimming boundary of that surface in UV space, you would see it looks like this:



So note there that the different portions of "seam" edges and also the top and bottom edge are all part of that outer trimming boundary in this case. I hope that may help explain what the full boundary is for this kind of case.

I would like to tune up the untrim mechanism in the future so that it could be smarter and not need to necessarily have the entire boundary selected to work, but for now you need to select all edges that make up a boundary for an untrim to work.

- Michael

Hi igor, just one more note:

> I was able to delete a trim curve on the backside of the
> cylinder,

Yup, that was because it was an interior "hole" boundary, so just that one edge defined an entire trim loop.


> but curve in front got splitted by seam edge of the cylinder and no
> matter what I try it refuses to be deleted))

That's because you were probably not selecting the entire trim boundary, the seam is basically like one of the "outermost" natural edges of the surface, when something intersects it, it becomes part of a longer loop for the exterior trim boundary rather than an interior hole trim.

To remove a boundary you need to select all of its edges (and they must not be attached to any other surface), so in this case with the piece that intersects the seam you must select the seam edges, and the top/bottom edges as well since they are all part of that trim boundary.

- Michael

One method :)
Close the seam by a line
Select this line and one half circle : Net Work
Same for other side

The half arcs circle must be not in one arc line so trim it in 2 arc lines
Network ABCDL in one time dont works!

Another solution :)
Copy rotate the hole circle
Trim keep Cylinder by this new circle
Rotate the new little circle
Union all ;)

Everyone, Thanks!
I was avoing to select all curves as was thinking it will erase my entire shape so i selected only those which formed hole.. - for inner trims it worked but not for the outer boundary trims

I'd better ask no more questions so that Michael had more time for MoI and possibly creating instances feature;))