How to avoid Mesh Distortion when Curves cutting themselves, especially with Subsurface Modifier?

Question

I am failing on a embarrassing challenge. I am trying to create an actually pretty simple form, but I cant finish my work without distortion on my mesh.

This is the object I am working on.

So far I tried different strategies, but I have always the same issue:

As you can see, the Boolean modifier and all my other attempts failed.

The problem is the overlapping mesh obviously, but I don't know how to fix it. My best attempt so far was to make the whole object from only 1 curve:

But then my Circle looks a not really symmetrically. And if you look closely enough you can still see a little shadow/distortion on the point where the curve hits herself.

Is there a common known workflow or something to help me finishing my project?

Answer 1

As you're talking about booleans it looks like you're open to do it with mesh (rather than only curve), so here is a solution:

• Create a torus (Major Segments: 24/Minor Segments: 8).
• Duplicate one of its circle, make it another object, extrude on the Z axis.
• Boolean the 2 objects.
• In Top Ortho view cut in half with the knife, then mirror the whole object.
• Use the knife to add some topology: K to activate, Z to cut through, C to cut orthogonally.
• Give your object a Subsurf and Shade Smooth to test the result.
• Use the same technic and also the Spin tool for the top of the object.