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When active, mirror mode causes all mesh geometry to be interepreted as one half of a shape symmetrically mirrored at the origin of the X axis. Either side of the X axis can be used as the "true" half of the model, and the "false" half will be calculated, drawn, and made interactive automatically. Any vertices positioned at exactly X=0 will not be mirrored, and will instead be shared by faces referencing them in both halves.

Mirrored faces are automatically reinterpreted in the opposite chirality as their unmirrored counterparts, preserving the definition of front and back sides. Surface normals (and tangents, where applicable) are also flipped on the X axis. All other vertex data is used as-is in the false half of the mirrored mesh.

This mode is intended to be used when modeling creatures or other objects that have perfect symmetry on one axis. This allows only the left or right half to be represented in mesh data, keeping the opposite half perfectly in sync with all geometry changes. Vertices, faces, and bones are mirrored automatically. Poses can separately reference each half of mirrored bones, allowing the mesh being posed to remain in mirror mode while applying an asymmetric deformation to it. [!todo]Currently, texture maps cannot separately reference each half of a mirrored mesh, requiring all texturing to be symmetrical. Asymmetric texturing of a mesh in mirror mode is planned as a future feature.

The [link=show_geometry_outline]geometry outline[/link], [link=show_mirrored_mouseover]mouseover highlight[/link], and geometry selection in the false half of mirrored geometry are shown in alternate colors to differentiate them from the true half. Mirrored geometry can be clicked to select it, but note that all adjustments take place in the coordinate system of the true half of the model. False half geometry is simply a proxy for the true half, and cannot be selected or manipulated separately.

See [link=mirror_clipping]Mirror Clipping[/link] for information on how editing mirrored geometry works when crossing mirror boundaries.

The false half of a mirrored mesh can be transformed into true geometry using the [link=operation_apply_mirror]Apply Mirror[/link] operation. This instantiates a copy of the true half of the mesh with mirror rules applied to it, allowing the two halves to subsequently be edited individually and asymmetrically. The opposite can be achieved with the [link=operation_slice]Slice[/link] operation, allowing all geometry on one half of the X axis to be discarded, after which the mesh can be placed into mirror mode for symmetrical editing.