Surface deformed after Boolean Union

After doing boolean union, the surface seems to get deformed.
There’s a streak of black area above the boolean union of two surfaces.
Even in rendering it stays that way.

Is there some don’ts in doing boolean operation?

Boolean_glass.3dm (783.5 KB)

It’s not the boolean operation that causes the problem. It’s the fact that your revolved cup is one single surface. I don’t know how it got that way, the profile has several sharp corners, so it should have been a polysurface. Single surfaces with kinks or internal tangent (G1) joints can cause meshing problems. If you run DivideAlongCreases with SplitAtKinks=Yes, the meshing problems will disappear. I also recommend you set SplitAtTangents=Yes in the same command.

This should not normally need doing, Rhino should split along creases automatically. Check the following setting - run the CreaseSplitting comand and see if SplitAlongCreases is set to Yes (default setting). If it is set to No, then that is the problem, set it back to Yes.

HTH, --Mitch

Than you for the reply.
I see. I did joined the curves just so moving them around was easier. I’ll group them from now on.
I’ll check the Creasesplitting command setting too.

Joined curves should normally not be a problem for Rhino as concerns sharp corners - these should be automatically split in any case (if CreaseSplitting is correctly set to Yes). If you revolve a group of unjoined curves, you will get unjoined surfaces.

For splitting or not at the internal G1 joints, that is set individually in each surfacing command - see the SplitAtTangents command line option in Extrude, Loft, Revolve, etc. I recommend to set that to Yes, unless you specifically need a single surface for mapping a texture or something.

–Mitch

Just to confirm, I should have a tick in the “Split Along Creases”?

I found that this was ticked off in the revolve command.

Thank you for the tip!