user: How do I use Options in Blender? Include parameters, examples, warnings and best practices.

assistant: [[image reference removed]](../../../_images/modeling_modifiers_generate_mirror_panel.png)

The Mirror modifier.

Axis
:   The X, Y, Z axis along which to mirror, i.e. the axis perpendicular to the mirror plane of symmetry.

    To understand how the axis applies to the mirror direction, if you were to mirror on the X axis,
    the positive X values of the original mesh would become the negative X values on the mirrored side.

    You can select more than one of these axes. And will then get more mirrored copies.
    With one axis you get a single mirror, with two axes four mirrors, and with all three axes eight mirrors.

Bisect
:   If the mesh is already on both sides of the mirror plane, it is cut by that plane,
    and only one side (the “positive” one by default) is kept to perform the mirror process.

Flip
:   When *Bisect* is enabled on an axis, you can use this setting to switch the side kept and mirrored
    (i.e. when it is enabled, the “negative” side will be kept, instead of the “positive” one).

Mirror Object
:   An [Object Selector](../../../interface/controls/templates/data_block.html#ui-data-id) to select an object (usually an empty),
    which position and rotation will be used to define mirror planes
    (instead of using the ones from the modified object).

    You can animate it to move the mirror axis.

Clipping
:   Prevents vertices from moving through the mirror plane(s) when you transform them in Edit Mode.

    If it is enabled but vertices are beyond the mirror plane and outside of the *Merge Distance*,
    the vertices will not be merged. But as soon as the vertices are within *Merge Distance*
    they are snapped together and cannot be moved beyond the mirror plane.

Merge
:   Where a vertex is in the same place (within the *Merge Distance*) as its mirror
    it will be merged with the mirrored vertex.

    Merge Distance
    :   The maximum distance between a vertex and its mirror copy at which they are merged together
        (being snapped on the mirror plane). Needs *Merge* to be enabled.

Bisect Distance
:   Distance from the bisect plane within which vertices are removed.

### Data

Flip UV
:   With this option you can mirror the UV texture coordinates across the middle of the image.

    E.g. if you have a vertex with UV coordinates of (0.3, 0.9),
    its mirror copy will have UV coordinates of (0.7, 0.1).

UV Offsets
:   Amount to shift mirrored UVs on the U/V axes.

    It’s useful for baking (as overlapping UVs can cause artifacts to appear in the baked map),
    so the UVs can be moved outside the image and not used for baking, but still be used for display.

Vertex Groups
:   Try to mirror existing vertex groups, with the following specific prerequisites:

    - The vertex groups you want to mirror must be named following the usual left/right pattern
      (i.e. with suffixes like “.R”, “.right”, “.L”, etc.).
    - The mirror side vertex group must already exist (it will not be created automatically).
      It must also be completely empty (no vertices assigned to it).

Flip UDIM
:   Mirror the texture coordinates around each tile center.