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Mesh Workbench

In one sentence: The Mesh workbench works with triangulated surface meshes — importing and exporting STL/OBJ/OFF files, analysing mesh quality, repairing defects, applying boolean operations, cutting meshes with planes or polygons, and converting between meshes and parametric solids.

What is a mesh?

A mesh is a collection of triangular facets that approximate a surface. Each triangle is defined by three vertices and a normal direction. Meshes are the simplest and most portable geometry format — used in 3-D printing (STL), game assets (OBJ), and scan data (PLY, OFF).

Meshes vs B-rep solids:

Property Mesh B-rep solid (Part/Part Design)
Geometry Triangles Exact surfaces (NURBS, planes, spheres)
Accuracy Approximate (depends on mesh resolution) Exact to floating-point precision
File size Can be very large (millions of triangles) Compact (topological description)
Editing Vertex, edge, facet level Feature-level (pad, pocket, fillet)
Primary use 3-D printing, scan data, game assets Engineering design, manufacturing

What is the Mesh workbench for?

The Mesh workbench serves several use cases:

  1. Importing scan data (photogrammetry, structured light, CT scans) in STL, OBJ, or PLY format for reference or reverse engineering.

  2. Preparing STL for 3-D printing — analyzing and repairing non-manifold geometry, filling holes, harmonizing normals.

  3. Converting solids to meshes — generating a triangulated mesh from a Part Design solid for export to STL.

  4. Working with mesh geometry — boolean operations, cutting, smoothing, decimating, segmenting.

  5. Unffolding flat meshes — the optional MeshPart Flatten tools produce flat layouts from curved mesh surfaces (requires flatmesh).

Key concepts

Manifold geometry

A manifold mesh is a watertight, connected surface where every edge is shared by exactly two triangles and no triangle intersects another. Non-manifold defects cause problems:

Defect Description Effect on 3-D printing
Open boundary Edge with only one adjacent triangle Holes in the surface
Non-manifold edge Edge with 3+ adjacent triangles Ambiguous inside/outside
Self-intersection Triangles penetrate each other Slicer errors
Inconsistent normals Mixed inward/outward facing triangles Inside-out geometry
Duplicate vertices Two points at the same position Disconnected facets

Inside vs outside (normal direction)

Every triangle has a normal that points "outward". For a closed solid, all normals must point away from the enclosed volume. If some normals point inward, the mesh is "inside out" in places — Harmonize Normals and Flip Normals fix this.

Typical workflows

STL → FreeCAD solid

1. Mesh → Import (load STL)
2. Analyze → Evaluation (check for defects)
3. Fix defects (Fill holes, Remove components, Harmonize normals)
4. Part workbench → Part → Convert to Solid  (or use ReverseEngineering)

Part Design solid → STL for 3-D printing

1. Design the part in Part Design workbench
2. Mesh workbench → Meshes → From Part Shape
3. Set mesh resolution (Max size = 0.5–1.0 mm for typical prints)
4. Meshes → Export → STL

See also