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Segmentation

In one sentence: Group adjacent triangles with similar normal directions and curvature into labelled regions — flat, cylindrical, spherical, or freeform — as a first step for reverse engineering.

Overview

Workbench: Mesh
Menu: Mesh → Meshes → Segmentation…
Command: Mesh_Segmentation
Shortcut: none

Segments the mesh by grouping adjacent triangles with similar surface normal directions and curvature properties into named regions. Each region is coloured distinctly in the 3-D view.

Intuition

A scanned part is one continuous triangle soup. Segmentation identifies which parts of that soup correspond to recognisable geometric primitives — flat walls, cylindrical bores, spherical domes — so each region can be fitted independently with Segmentation — Best Fit or the Reverse Engineering workbench.

When to use it

  • First step in a reverse-engineering workflow: identify surface types before fitting exact primitives.
  • Isolating a specific surface region (e.g., a bore) for curvature measurement.
  • Analysing the surface composition of an imported scan.

When NOT to use it

  • Don't use it on noisy meshes without smoothing first — scan noise creates spurious curvature variations that corrupt the segmentation. Apply Smoothing before segmenting.

Step-by-step

  1. Select the mesh.
  2. Choose Mesh → Meshes → Segmentation….
  3. Configure which surface types to detect (plane, cylinder, sphere, freeform) and their curvature thresholds.
  4. Click OK. Regions are coloured in the 3-D view.
  5. Follow up with Segmentation — Best Fit to fit exact primitives to each region.

Parameters

Parameter Description
Smooth mesh Pre-smooth before segmenting to reduce noise
Plane Detect flat regions; set max plane curvature
Cylinder Detect cylindrical regions; set min/max cylinder radius
Sphere Detect spherical regions; set min/max sphere radius
Freeform Classify remaining triangles as freeform
Max curvature Maximum curvature for freeform classification

Common mistakes and pitfalls

Smooth the mesh before segmenting

Scan noise produces high-frequency curvature variations. Without smoothing, many triangles are misclassified as "freeform". Apply Smoothing first.

Segmentation is sensitive to threshold settings

A very tight curvature threshold for "plane" will miss slightly curved flat faces. Start with generous thresholds and tighten as needed.

See also