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Trim by Polygon

In one sentence: Draw a closed polygon on screen and keep only the mesh elements inside the polygon boundary, removing everything outside.

Overview

Workbench: Mesh
Menu: Mesh → Meshes → Cutting → Trim by Polygon
Command: Mesh_PolyTrim
Shortcut: none

Similar to Cut by Polygon, but always removes the mesh elements outside the drawn polygon and retains the elements inside. The result has the polygon outline as its boundary.

Intuition

Trim by Polygon is a shorthand for "Cut by Polygon → keep inner". Use it when you want to crop a mesh down to a specific 2-D outline — for example, keeping only the scan data within a particular region of interest.

When to use it

  • Cropping a scan mesh to a region of interest defined by an outline.
  • Removing everything outside a specific screen-drawn boundary in one step.

Step-by-step

  1. Align the 3-D view to the cut plane (use a standard view in orthographic projection).
  2. Choose Mesh → Meshes → Cutting → Trim by Polygon.
  3. Left-click to add polygon vertices.
  4. Right-click to close the polygon — everything outside is removed.

Common mistakes and pitfalls

Cut is performed in 2-D screen space

Use orthographic projection and a standard view (Top/Front/Side) for predictable results. Perspective or off-axis views produce oblique cuts.

Result has an open boundary

The trimmed edge is an open boundary. Use Fill Up Holes if you need to close it.

See also