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I'm trying to combine three spheres in a way that I can be able to modify the crease, like making the crease sharper or more round. I've tried using boolean but it doesn't come out quite right when I use subdivision modifier or when I use smooth shade. three spheres

three spheres using boolean and smooth shade

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3 Answers 3

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You might consider using metaballs for this.

You'll get a clean-ish quad based topology but may have limited control over bevel radius for the unions.

enter image description here

Go to Add > Metaball > Ball. In the Properties Window > Object Data tab, increase the detail by lowering the Resolution Viewport to a lower value like $0.05$, adjust Resolution Render accordingly.

Enter Edit Mode and from the Properties Toolshelf, under Item > Transform increase the Stiffness value to $10$ or above. Values higher than $10$ can apparently only be achieved by scaling in the viewport with S, typing in higher numbers doesn't seem to work.

Exit Edit Mode and duplicate the spheres using ⇧ Shift + D and place them at will.

Meta objects will naturally ensure a rounded bevel over the joints, and will also update live as you move them around. Topology will not naturally follow object shape though, like manual modelling would.

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    $\begingroup$ By "Metal" do you mean shading? $\endgroup$ Commented Jun 8, 2022 at 21:21
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    $\begingroup$ @MarkusvonBroady meta* :p $\endgroup$ Commented Jun 8, 2022 at 21:22
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    $\begingroup$ @MarkusvonBroady I meant internet slang for brutal and edgy like the music genre. :D Just kidding, silly typo, Thanks for the correction, Allen $\endgroup$ Commented Jun 8, 2022 at 21:44
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To get a clean Boolean, topology must line up exactly.

If you're doing that with UV spheres, figuring out how many rings, segments, tweaking scale and distance to get topology to match, can be a real pain. Geometry Nodes begins to bring parametric modelling to Blender, so it might be worth hacking together a tool like this..

enter image description here

.. which makes it much easier to adjust everything, while working under further Bevel and Subdivision Modifiers. If you set the Bevel 'Inner Miter' to 'Arc', you can get control over the central intersection by adjusting its spread.

enter image description here

The tool could be generalized.. supposing you were doing molecular modelling, or something, you could set the instancing framework as a parameter.. or the modifier could be kept in the bottom drawer and re-hacked for other one-off jobs.

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    $\begingroup$ That's an impressive approach I would not have thought of. The result looks really nice. Complicated to set up, yes, but really clean topology with a very low polygon count! $\endgroup$
    – Ben
    Commented Jun 9, 2022 at 13:41
  • $\begingroup$ Thanks, @Ben ! I've often built temporary jigs for accuracy, as snapping targets, etc., for geometric modelling, but now you can often build a re-usable modifier in about the same time. :) $\endgroup$
    – Robin Betts
    Commented Jun 9, 2022 at 17:37
  • $\begingroup$ I was thinking about geonodes, but didn't occur to me to make the axes parallel - seems obvious once you see the answer. Also, is boolean even needed? Isn't it topologically a cylinder with adjusted vertex positions? $\endgroup$ Commented Jun 9, 2022 at 22:00
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    $\begingroup$ @MarkusvonBroady This one does start with a cylinder ... agreed... the problem is rather niche :) $\endgroup$
    – Robin Betts
    Commented Jun 10, 2022 at 10:20
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    $\begingroup$ @RobinBetts Oh yeah, I meant the answer as opposed to the comment. $\endgroup$ Commented Jun 10, 2022 at 10:21
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You could try with an UV sphere or with a cube that you subdivide:

enter image description here

Then boolean and only keep 1/4th of the result, rework the topology a bit:

enter image description here

Give it a Mirror and a Subdivision Surface:

enter image description here

If you want the seam to be sharper you'll just need to add edge loops:

enter image description here

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