Recently had an issue with the mirror modifier. I've searched around and tried a few things but nothing seems to be fixing my problem. A few days prior everything was working fine.

Tried resetting default settings and even reinstalling but the problem still remains.

Also tried all the suggestions in this video below: https://www.youtube.com/watch?v=-ioeQAhxkb8

enter image description here

So something as simple as trying to mirror this half roundcube the mirror doesn't apply automatically. I usually click the modifier and it should apply instantly and then I would add the clipping.

What could be the problem?

Any suggestions is much appreciated.

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1 Answer 1


Your mesh's vertices are placed in the negative Y direction. To mirror them to the positive Y direction, you have to set the Mirror modifier's Axis to Y, not X.

mirror axis

  • $\begingroup$ Thank you so much, didn't know it was effected that way. Is there a way to have it autodetect the mirror axis when pulled on certain Axis? $\endgroup$
    – lefthanded
    Jan 25 at 8:40
  • $\begingroup$ @lefthanded modifiers operate in Object Space. If you want to see what that orientation is, go to the Object tab > Viewport Display panel, and check 'Axis' . (The XYZ axes are always displayed at unit length, as scaled by any object-level transforms, so may be hidden inside the mesh) $\endgroup$
    – Robin Betts
    Jan 25 at 8:50
  • 1
    $\begingroup$ @RobinBetts Good point. Of course the mirror modifier in the question would have worked with X mirroring, if the object was rotated 90° on the Z axis without having the rotation applied. I was assuming the most simple case that the object had the same orientation as the world space which made the incorrect setting very obvious. $\endgroup$ Jan 25 at 8:54
  • $\begingroup$ @lefthanded You didn't know it was effected that way? But did you never wonder what the axes to choose from are for...? Anyway, no it's not autodetecting unless there exists an addon which does that (but I don't know of any), also how should that work? How should the modifier predict what you want to do? An object to mirror does not need to have a connection in the center. So you may have mesh lying solely in the -Y and -X and -Z area. Does that mean you want to mirror it on all 3 axes to the positive side? Not necessarily. And which axis/axes should the modifier choose then? $\endgroup$ Jan 25 at 15:28

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