Skip to content

Cross-Sections

In one sentence: Generate multiple evenly spaced parallel cross-section wires through a shape at once — all cross-sections in one operation.

Overview

Workbench: Part · Menu: Part → Cross-Sections
Toolbar: Part Boolean · Shortcut: none

Cross-Sections is a dialog-based tool that creates many parallel cross-section wires through a shape simultaneously. You choose the axis, spacing, and count. Each cross-section is a Section wire — a 2-D outline at that height.

Intuition

Where Section computes one cross-section at a time, Cross-Sections generates a series: imagine slicing a loaf of bread — you get all the slices at once rather than cutting one by one. The result is a compound of wires.

Uses: - Extracting a family of cross-sections for a loft or FEA mesh. - Generating station lines for ship hull or aircraft analysis. - Creating slice data for 3-D printing (slicer approximation).

Step-by-step walkthrough

  1. Select the shape to section.
  2. Part → Cross-Sections.
  3. In the dialog:
  4. Select the axis (X, Y, or Z).
  5. Set the start and end positions.
  6. Set the count of sections (or spacing).
  7. Click OK.
  8. A compound of parallel wires appears.

Parameters

Parameter Type Description
Axis XYZ enum Direction perpendicular to the cutting planes
Position start Distance Where to start the first section
Position end Distance Where to end the last section
Count Integer Number of evenly spaced sections

Python API

import FreeCAD as App
import Part

doc = App.newDocument()

sphere = doc.addObject("Part::Sphere", "Sphere")
sphere.Radius = 20.0
doc.recompute()

# Generate cross-sections manually at specific Z heights
sections = []
for z in range(-15, 20, 5):   # Z = -15, -10, -5, 0, 5, 10, 15
    plane_shape = Part.makePlane(60, 60, App.Vector(-30, -30, z))
    wire = sphere.Shape.section(plane_shape)
    if not wire.isNull():
        sections.append(wire)

compound = Part.makeCompound(sections)
feat = doc.addObject("Part::Feature", "CrossSections")
feat.Shape = compound
doc.recompute()
print(f"Number of cross-sections: {len(compound.Wires)}")

Common mistakes and pitfalls

Empty sections at extremes

If the start or end position is outside the shape's bounding box, some sections will be empty wires. Trim the range to the shape's extent.

See also