Boolean Union- ONE MORE TIME

I’ve tried everything (that I know) and I can’t get this groove closed. I have two good polysurfaces (according to ‘what’), verified that they are solids. but BU fails every time! Any ideas/tips?


no any idea. :no_good_man:
would be very useful to share the file or, at least a screenshot of them.
the best would be to share both.


boolean union works with the intersection, if the intersect command shows more than a single closed curve en each area, the program doesn’t know what to do. the common case of this is when you have multiple coincident surfaces.

I attached the file that contains both objects.

Don’t the two solids have to overlap to enable the union? I.E. to plug a hole.

File attached again Hmm, for some reason it quits ~halfway through. It’s 148MB. Is there a limit? I’ll try zipping it. Zip is 40MB, but it still won’t load. I tried uploading & drag & drop. No joy.

Are those 2 solids the only objects in your file? If not, perhaps try creating a new file where you only save those 2 objects to decrease file size.

Yup, everything else deleted.

Let’s try a pruged version! WOWUnion-fail-P.3dm|attachment (2.1 MB)

I tried another version where the filler was exactly the same size as the groove. Same result. :nauseated_face: Revised model attached.Union-fail-2P.3dm (2.1 MB)

Hello - it is not clear to me what you’re trying to accomplish with a Boolean here - If you wan to remove that groove, ExtractSrf the surfaces that make up the groove, plus the flat face that it is cut into and delete these surfaces, then run Cap on the remainder - does that do what you need?

Union-fail-2P_PG.3dm (1.0 MB)


if you run the intersect command, this is the result :

a bunch of open curves. that’s why the boolean fails

I don’t understand why they are open, both were created by revolve which resulted in a uniform closed poly surface.

Yest that does what I want, but I still don’t understand why union didn’t work with two overlapping solids.

Hello - it is also a much better way to accomplish what you need - dealing with Rhino objects as surfaces is often a much cleaner way to work than as solids - Rhino is primarily a surface modeler after all. As to why your attempts failed, Boolean operations depend upon getting clean curves of intersection. When surfaces on the objects involved are coincident or nearly coincident, getting those clean curves is made much more difficult and subject to error. Generally you’ll want objects with clear, clean intersections as inputs.