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From Part Shape

In one sentence: Tessellate a B-rep solid into a triangulated mesh, ready for 3-D printing export or mesh-based analysis.

Overview

Workbench: Mesh
Menu: Mesh → Meshes → Create Mesh from Shape…
Command: Mesh_FromPartShape
Shortcut: none

Converts a B-rep solid (from Part Design, Part, or other parametric workbenches) into a Mesh::Feature containing a triangulated mesh. This is the standard workflow for preparing a parametric model for 3-D printing.

Intuition

B-rep geometry is mathematically exact (curved faces, precise edges) but 3-D printers only understand triangles. From Part Shape samples the B-rep surface at a controlled density to produce a triangle mesh that approximates the solid.

The quality of the mesh (how closely it matches the true geometry) is controlled by two parameters: surface deviation and angular deviation.

When to use it

  • Preparing a Part Design or Part solid for 3-D printing (export to STL).
  • Converting parametric geometry to a mesh for mesh-based analysis.
  • Generating a reference mesh for comparison with a scanned part.

When NOT to use it

  • Don't use it as a final step — the resulting mesh is a snapshot. If you modify the solid, re-run From Part Shape to get a fresh mesh.
  • Don't use it for exact B-rep-to-B-rep conversion — use File → Export with STEP or IGES for that.

Step-by-step

  1. Select the solid in the model tree (Part Design Body, Part shape, etc.).
  2. Choose Mesh → Meshes → Create Mesh from Shape….
  3. The Tessellation dialog opens.
  4. Set the tessellation parameters (see below).
  5. Click OK. A Mesh::Feature appears alongside the solid.
  6. Export with Export Mesh → STL.

Parameters

Parameter Description Typical value
Surface deviation Max error between mesh and true surface (mm) 0.1–0.5 mm
Angular deviation Max angle between adjacent triangle normals (°) 5–10°
Relative surface deviation Express deviation as fraction of bounding box Off for absolute
Apply face colors Preserve face colours from Part Design Optional
Define segments by face colors Create mesh regions per colour Optional

Resolution guide

Use case Surface deviation Angular deviation
FDM 3-D printing (0.2 mm layers) 0.2 mm 10°
SLA/resin printing 0.05 mm 5°
Visual rendering 0.5 mm 15°
Fine detail 0.01 mm 2°

Common mistakes and pitfalls

From Part Shape does not link to the solid

The generated mesh is a static snapshot. If you modify the parametric solid, you must re-run From Part Shape to get an updated mesh.

Very fine tessellation creates huge files

Surface deviation of 0.01 mm on a complex part can produce millions of triangles — a file too large for most slicers. Use the coarsest setting that meets your print resolution.

Python API

import MeshPart
import FreeCAD as App

doc = App.ActiveDocument
body = doc.getObject("Body")

mesh_data = MeshPart.meshFromShape(
    Shape=body.Shape,
    LinearDeflection=0.1,      # surface deviation in mm
    AngularDeflection=0.087,   # 5° in radians
    Relative=False
)

mesh_feature = doc.addObject("Mesh::Feature", "Mesh")
mesh_feature.Mesh = mesh_data
doc.recompute()

See also