Boolean union fails with identical revolved surfaces

In my previous post, I had some revolutions where the axis was off. Merging faces caused Rhino to lock up.

In trying to correct that, I have taken the Red revolution and copied it around the center 120 and 240 degrees.

I can Boolean Union the Red and Purple to Black BUT I cannot do so with the blue. I cannot split black using blue either.

I am curious why this is the case.

Revolve Problem.3dm (3.4 MB)

try this one… _BooleanUnion then _MergeAllFaces should work.

Revolve Problem_J.3dm (3.6 MB)

(i didn’t really investigate what the exact problem is with your model… just modeled the nodes fresh (well, extracted the seam from one of yours then revolved it, aligned it with the larger object, then polar arrayed it)

I suspect it is to do with the isocurve lining up with your blue object (rotating the central element a bit solved the issue). Merge all faces still a problem though.

I am puzzled why yours worked in mine does not. I have been playing with all kinds of variations here and am unable to create one the does a union of some sorts.

See if this can help. The underlying problem is the nodes and their arrangement.

Revolve Problem.3dm (6.6 MB)

Thanks but I am puzzled by what is going on here to fix this.

Hi Jeff - yours is slightly different in that the center of the little revolves fall on the edge of the big circle - I noticed that Jim’s do not, quite. My guess of the moment is that the original placement makes the singularity of the spherical ends intersect the large revolve right on a knot-line, and in yours it misses. At any rate, bug noted for V6:

Jim, thanks for sending this in.


I did a test in moving the blue object just a minute distance (0.0001’) away from the center of the big object, not all the way to the edge, and the booleanUnion succeeded.