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Merge

In one sentence: Combine two or more separate mesh objects into a single Mesh::Feature containing all their triangles.

Overview

Workbench: Mesh
Menu: Mesh → Meshes → Merge
Command: Mesh_Merge
Shortcut: none

Combines two or more Mesh::Feature objects into a single mesh object. The meshes are appended into one data structure — they need not be touching or overlapping. The original mesh objects are retained.

Intuition

Merge is the mesh equivalent of "make a compound" in the Part workbench: it groups multiple separate mesh objects into one tree entry without altering their geometry or computing any intersection.

Merge Mesh Union
Combines objects Yes Yes
Computes topology No — appends triangles Yes — resolves intersections
Requires solid meshes No Yes
Result One object (may be multi-component) Single fused solid
Speed Instant Slower

Use Merge for organisation (one object instead of many). Use Union when you need a single topologically fused solid mesh.

When to use it

  • Combining scan fragments (separate files) into one mesh for analysis.
  • Grouping mesh components back together after separate processing.
  • Reducing the number of objects in the model tree.

When NOT to use it

  • Don't use it when you need a fused solid — use Mesh Union instead.

Step-by-step

  1. Select all meshes to merge (hold Ctrl to multi-select).
  2. Choose Mesh → Meshes → Merge.
  3. A new Mesh::Feature appears containing all triangles. The originals are retained.

Common mistakes and pitfalls

Merge does not fuse meshes

The merged object may contain multiple disconnected components. It is not a manifold solid. Use Mesh Union if you need a fused solid.

Python API

import Mesh
import FreeCAD as App

m1 = App.ActiveDocument.getObject("Mesh")
m2 = App.ActiveDocument.getObject("Mesh001")

combined = m1.Mesh.copy()
combined.merge(m2.Mesh)

merged = App.ActiveDocument.addObject("Mesh::Feature", "Merged")
merged.Mesh = combined
App.ActiveDocument.recompute()

See also