Hi Martin, it looks like the sweep is having a problem with the miter joint.

When you do a 1-rail sweep along a path that has a sharp corner in it, the sweep will place a miter joint between the 2 different segments of the path where they meet at a sharp kink type area.

That's done by a process of extending the surfaces and then intersecting them with one another. When the rail is a swoopy 3D curve instead of a 2D curve it can be pretty difficult for the pieces to completely intersect with one another and you can get just the extensions coming through which I believe is the artifact that you're seeing there.

For a 3D swoopy path curve you may want to make sure that the rail is totally smooth and does not have any sharp kink areas in it, for a smooth path it won't try to do mitering or if you do want to do a path with a sharp kink in it you may need to do the sweep in different sections for each separate segment instead of having a joined rail with a kink in it, and possibly have profiles positioned at the start and end of the segments so that you can control how the pieces meet up.

But yeah what you show there can be the result of trying to get a mitered corner at sharp junctures on a swoopy 3D path curve.


EDIT: 12/5/2018 - added makeExternalThreadv4.zip fixes some missing end tags that caused problems in MoI v4.


- Michael