i've made a mistake - modeled a complex (consisting of a number of meshes) object without a mirror modifier.

and now i came to unwrapping and decided to use mirror modifier. but stuck. i don't know how to split this object into halves, because tools i know (knife, edge loop, bisect) won't do it.

i was adviced to use boolean modifier first with a cube. it seems to work, but may be there is some simplier way?

EDIT: boolean worked only on somehow simple objects, but failed on something more complex.

here is the image: enter image description here it is perfectly symmetrical. it not always has edges in the middle, but i think it's not a problem (faces there are flat)?

here is the blend: http://www.pasteall.org/blend/43072

  • $\begingroup$ Does the geometry have a straight edges at the center,where the cut would be made? $\endgroup$
    – Omar Emara
    Aug 11, 2016 at 7:41
  • $\begingroup$ It largely depends on the object. Can you add an image to your question? $\endgroup$
    – Timaroberts
    Aug 11, 2016 at 7:42
  • $\begingroup$ and is your model totally symmetrical ? $\endgroup$
    – lemon
    Aug 11, 2016 at 7:42
  • $\begingroup$ Could you split the object into multiple, boolean that and recombine them? $\endgroup$
    – Bradman175
    Aug 11, 2016 at 9:45
  • $\begingroup$ The knife tool would work for this. Follow my answer, but also press Z before making the cut. $\endgroup$
    – David
    Aug 11, 2016 at 15:25

2 Answers 2


'Knife project' works well here :

  • Add a plane
  • Place one of its edges along the middle (at the exact center)
  • You may work in a ortho view and along the axis (here top ortho)
  • Stretch it so that it covers your mesh
  • Select your mesh (keeping the plane selected) and enter edit mode
  • Hit 'knife project' and make sure the option is 'cut through'
  • Select the half to remove and add the mirror modifier

enter image description here

  • $\begingroup$ wow! cool! thank you! i have never used this tool and thought it something identical to simple knife, lol $\endgroup$ Aug 11, 2016 at 10:14

In Blender 2.83 I've had success using the knife tool but it's a little different than above. This will only work with symmetrical objects.

  1. Switch to whichever ortho view you want
  2. Select the knife tool.
  3. Click the most top and most middle edge, close to where half would be. You should then see some key functions show up in the bottom bar of the screen.
  4. Press Z to toggle the cut-through option. This will cut through the whole object. By default this is off and it would only cut the viewable faces.
  5. Hold Ctrl to snap to the middle of edges. You should notice the first vertex where you clicked shift slightly to the center (or maybe not at all if you were perfect).
  6. Continue holding Ctrl and move the mouse to the most bottom middle edge and click. Then double click again on that vertex to close the cut.

Check out the cut in mesh mode to make sure it went all the way through, then press Enter to finish the cut. You can now split the object at this line for two perfect halves.


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