Mirror Modifier

Control the Mirror Modifier in Blender – PART 2

Today we look at a more precise intuitive way of using the mirror modifier. See Part 1 for a description of the “default” way to use it.

Let’s take another look at our simple object, but this time we see that the face/plane we want to use for a mirror is not orthogonal, in fact it can be any inclination in any plane:

The mirror face/axis is not orthogonal

If we try to mirror this object using the previously discussed method, this is what happens:

This just mirrors across the Y axis which doesn’t give us the desired result

The best way to control a mirror operation is to mirror the object about another object. In this case we only have one object in the scene, so we need to construct a mirror object or plane. To mirror across the indicated face, the easiest approach is to construct a grid object on the plane.

Switch to Edit mode Tab Key and select Face mode by pressing 3 Key. Select the face we want to put the grid object onto:

Select this face

Now we change our view to look directly at the selected face orthogonally. We do this with Shift keyNumpad 7 key. Or we could use the Align View menu:

If you can’t remember the shortcut…

The view changes to this:

The view is now orthogonally aligned to the selected face

Next, we want to place the cursor onto that face. Type Shift keyS key:

Click Cursor to Selected

The cursor jumps to the middle of the face.

Now, switch back to Object mode Tab Key , and type Shift keyA key and insert a new Grid object:

Click Grid

After clicking Grid, the Add Grid panel appears. Change the Align parameter to View:

Click the Align drop-down arrow and choose View
The Grid object appears on the face

The wireframe view of the grid looks like this:

The Grid object (selected) and the original object (unselected)

We chose a grid object instead of a plane object because it is then very easy to confirm that it is correctly placed.

Now the mirror operation is very straightforward. Select the object to be mirrored. Add a Mirror modifier to it. Click in the Mirror Object box and select Grid from the dropdown.

Choose Grid for the Mirror Object or click the eyedropper and then click the grid.

While still in the Modifier panel, click each Axis box in turn and choose the appropriate axis. (In this case it will be Z) :

The mirrored object

The object is now mirrored using the Grid object as the mirror plane. This has the enormous advantage that the mirror is exact, and the original object does not have to move. The grid plane can, of course, be orthogonal, whereby you will get the same effect as the method described in Part 1 except that it will be more precise.

To finish up,

  • Apply the modifier
  • Delete the Grid Object
  • Delete the internal face.

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