Boolean Union causes pipe to disappear


I am trying to BooleanUnion two stars together using a Pipe but when I do the Pipe disappears, leaves an indent in one star and nothing in the other one. I have checked about 20 previous posts and to try to resolve this I have:

  1. Moved the Pipe to make sure they Intersect, well think they do…
  2. Explode Pipe, removed end surfaces, Cap it and Join to create a polysurface rather than a Surface
  3. Checked the Boolean Intersection, although with this I was just left with the Pipe which curved shape either end which I am not sure is right or wrong.

I think the problem is with the Star itself, which has been created using Project on a Sphere, then Extrude to create the depth before Offsetting to create the solid followed by FilletSrf. However, not sure what the problem is so any help would be appreciated. Thanks

Star_0.3a_Check.3dm (7.0 MB)

What you didn’t check is to see if the polysurfaces were closed and valid or not. In your case both the stars are open and the normals are facing inwards. Boolean operations use the surface normals to determine which parts to keep and which to throw away. When things are open and inside-out, the operations may have unexpected results.

In your case everything’s pretty much a mess, the stars have a bunch of naked edges, the inside corners are too tight and have folds as well. You should probably consider remaking them from scratch (and radially symmetrical, which they are not).

I think you need to start with a clean lower star profile with a defined center, plus an arc profile of the top surface, revolve, extrude, offset, trim and join as necessary to get a clean solid. Then add the top fillet last. Check your result to make sure it’s good and closed. Then your Boolean operations should work.


There was me checking Select Bad object thinking that all was ok if nothing was found. LOL.

Will remake from scratch and thank you for reminder about naked edges, been a while since I’ve used Rhino and couldn’t remember term. Won’t forget it now! Thanks.