- use mirror when the option is enabled in editmode. - fliped group names are used when they exist. - only the setting that is edited will be applied to the mirrored verts group. - copy value is applied to all mirrored verts of the selection. - normalize normalizes all vgroups and mirrors. utility functions defvert_sync and defvert_sync_mapped, similar to defvert_copy but does not remove existing groups and optionally creates groups as needed. defvert_sync_mapped uses a an int array for mapping the flipped values.