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Section

In one sentence: Find the cross-section wire where two shapes intersect — the 2-D curve that lies exactly on both surfaces simultaneously.

Overview

Workbench: Part · Menu: Part → Section
Toolbar: Part Boolean · Shortcut: none

Part Section computes the intersection wire between two shapes. Where Boolean Common returns the overlapping volume, Section returns only the curve (edge or set of edges) where the two surfaces meet. The result is a wire or edge, not a solid.

Intuition

If you press a flat plane into a sphere, the contact curve is a circle. That circle is the Section of the sphere and the plane. Section is a pure 2-D intersection result — it gives you the outline rather than the volume.

Common uses: - Generating a cross-section profile for further use as a sweep or loft section. - Finding the intersection curve between an imported surface and a plane, to extract a 2-D outline. - Design verification — check where two components touch.

When to use it

  • You need the intersection curve between two shapes (not their shared volume).
  • You want to extract a planar cross-section wire from a solid.
  • You need the contact boundary between a mating surface and its seat.

When NOT to use it

Step-by-step walkthrough

  1. Select the first shape (the shape to section).
  2. Ctrl+click the second shape (the cutting/sectioning shape — often a flat plane or a datum plane).
  3. Part → Section.
  4. A Part::Section wire object appears.

Parameters

Parameter Description
Base First shape
Tool Second shape (sectioning plane or solid)

Python API

import FreeCAD as App
import Part

doc = App.newDocument()

# Sphere to section
sphere = doc.addObject("Part::Sphere", "Sphere")
sphere.Radius = 20.0

# Cutting plane (thin box as plane substitute)
plane = doc.addObject("Part::Box", "Plane")
plane.Length = 60; plane.Width = 60; plane.Height = 0.001
plane.Placement = App.Placement(App.Vector(-30, -30, 10), App.Rotation())
doc.recompute()

# Section
section = doc.addObject("Part::Section", "SectionWire")
section.Base = sphere
section.Tool = plane
doc.recompute()

# The result is a circle wire at Z=10
print(f"Section shape type: {section.Shape.ShapeType}")   # Wire
print(f"Length: {section.Shape.Length:.2f} mm")           # circumference

See also