ZBrush Tip: Restore bilateral symmetry with Mirror And Weld in ZBrush

When symmetry breaks, Mirror And Weld is the fastest, cleanest way to restore perfect bilateral alignment and a sealed center seam.

Setup and preparation:

• Clear obstructions: Ctrl+drag on the canvas to clear masks; Ctrl+Shift+click on the canvas to show all.
• Verify the axis: Turn on Transform > Activate Symmetry (X) and the Floor to confirm the world axes.
• Center to world: Use Tool > Deformation > Unify sparingly (resizes to ZBrush units), or keep scale and zero the pivot with the Gizmo 3D (click the center icon) so the midline sits at X=0.
• Check mesh integrity: Tool > Geometry > Mesh Integrity > Check Mesh, then Fix Mesh if needed. Remove stray points before welding.
• Drop to lowest subdivision level before topology changes to avoid losing detail on higher levels.

Choosing the side to keep:

• Mirror And Weld copies from the negative side of the chosen axis to the positive side by default.
• If your “good” side is on +X, first run Deformation > Mirror (X), then run Mirror And Weld. This ensures the correct source side is used.
• Use the appropriate axis (X for characters, Y for vertical objects, Z for depth-oriented assets) depending on your model’s orientation.

Execute the weld:

• Go to Tool > Geometry > Modify Topology > Mirror And Weld.
• If a seam doesn’t close, adjust Weld Distance (Modify Topology > WeldDist) incrementally until the centerline fuses without collapsing nearby edges.
• If nothing happens, the mesh likely doesn’t cross the world center or you’re on the wrong side; re-center or use Deformation > Mirror and try again.

Preserving detail and UVs:

• Non-destructive approach: Duplicate the SubTool, ZRemesh with symmetry on to establish a clean centerline, Mirror And Weld, then Project All from the original to recover details.
• Perform Mirror And Weld before UV creation. Mirroring geometry after UVs typically invalidates or overlaps shells.

Handling polygroups and color:

• After welding, use Tool > PolyGroups > Group By Normals or Auto Groups to restore clean logical groups across the seam if needed.
• To mirror color information, use Tool > Polypaint > Mirror And Weld (mirrors from negative to positive on the chosen axis).

Troubleshooting and best practices:

• Visible seam after weld: Slightly Move brush the centerline, Smooth lightly, and apply Polish By Features for a uniform junction.
• Asymmetry without a clean cut: Try Deformation > Smart Resym. Mask the “good” half and run Smart Resym to transfer it to the other side without topology changes.
• Off-axis models: With the Gizmo 3D gear icon, use Reset Mesh Orientation, then re-check which axis to mirror on.
• Multiple SubTools: Fix each SubTool individually for consistent symmetry; SubTool Master can help batch visibility and duplication steps.

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