Symmetry allows users to apply mirrored actions across a chosen axis simplifying the creating of symmetrical objects. Once Symmetry is enabled, any operations performed in the component modes (vertex, edge, polygon) such as selecting polygons or deforming edges will be likewise mirrored across the chosen axis. However, prior to enabling symmetry, users will need to make sure the model itself is perfectly symmetrical as modo applies symmetry operations to corresponding vertex positions. Users also need to ensure that the model is located perfectly centered at the item layers world origin (0,0,0 location). This can be accomplished by applying one of the Center commands available in the toolbox of the two modeling layout tabs, or in the menu bar under the "Edit > Center Selected" menu. Additionally, users can use the Symmetry Tool to force a models topology to match symmetrically across an axis, resolving any issues that may cause symmetry to break.
Symmetry can be enabled using the Symmetry pop-up on the modo Modes Toolbar or within the menu bar under "Edit > Symmetry" and choosing an axis to mirror across. Symmetry always works in model space, by default, in relation to the Center position of the item layer. The user can edit the settings of Symmetry using the 'Symmetry Options' available in the menu bar under "Edit > Symmetry Options...".
Active: Enabled/Disables the symmetry function.
Axis: Choose which planar axis that Symmetry works over or 'Arbitrary' to define your own custom axis.
Arbitrary Axis: The symmetry axis is defined by a vector and center position, 'Arbitrary Axis' allows the user to set a custom axis vector.
Offset: Defines a symmetry position away from the origin, parallel to the base symmetry plane.
Workplane: When 'Enabled, symmetry will respect the Work Plane, but keep in mind as the Work Plane position is modified, the mesh must still have corresponding symmetrical geometry.
UV Active: Enabled/Disables the application of symmetry in the UV Viewport
UV Axis: Choose which axis that Symmetry works across, 'U' is vertical, 'V' is horizontal.
UV Offset: Defines a symmetry position away from the UV origin.
TIP: In certain instances of extreme asymmetry on a model, a quick and dirty way to make certain a model is symmetrical is to simply delete half of the model (making sure symmetry is disabled for this operation) and then use the Mirror command with an Action Center set to 'Origin'.
