Persistent Section Cut¶

In one sentence: Apply a live clipping plane to the 3-D view that continuously shows a cross-section of all visible objects — a permanent, interactive viewport cut that does not modify the actual geometry.

Overview¶

Workbench: Part · Menu: Part → Persistent Section Cut
Toolbar: Part Analysis · Shortcut: none

Persistent Section Cut adds an interactive clipping plane to the FreeCAD 3-D viewport. The plane can be positioned along X, Y, or Z (or at a custom position), and the view updates in real time as you drag the cut position. The actual Part geometry is never modified — this is a view-only operation.

Intuition¶

Section views are essential for understanding internal geometry: seeing whether two parts actually touch, checking wall thicknesses, and verifying clearances without disassembling the model. Persistent Section Cut is the "X-ray mode" of the Part workbench.

Unlike Section which creates a permanent wire object, Persistent Section Cut is non-destructive: toggle it off to restore the normal view.

When to use it¶

Inspecting internal geometry of a complex assembly or housing.
Verifying that two mating parts fit correctly without interference.
Generating section-view screenshots for documentation.
Checking wall thicknesses and internal clearances visually.

When NOT to use it¶

Generating a section wire for further modelling — use Section.
Multiple parallel cross-sections — use Cross-Sections.

Step-by-step walkthrough¶

Part → Persistent Section Cut.
A Section Cut panel appears.
Choose the cut axis (X / Y / Z).
Drag the slider or type a position value to move the clipping plane.
Toggle the checkboxes to cut in X, Y, or Z simultaneously (multiple simultaneous clip planes are supported).
Click the refresh button if the view does not update automatically.
Close the panel to restore the full view.

Parameters¶

Parameter	Description
Cut X / Y / Z	Enable/disable clipping on each axis
Position X / Y / Z	Position of each clipping plane along its axis
Flip	Flip the clipping direction (cut the other side)

Common mistakes and pitfalls¶

Section Cut is a view tool — geometry is unchanged

Closing the panel or toggling off the cut restores the full view. The Part geometry was never modified. Do not confuse this with Section which creates a permanent geometry object.

Performance with many objects

Persistent Section Cut clips every visible object in the scene. On large assemblies with many high-polygon bodies, dragging the slider may be slow. Hide objects you don't need to inspect.

Python API¶

The Persistent Section Cut is a GUI tool with no direct Python API for programmatic control. For scripted cross-section generation, use Section or Cross-Sections.

# For programmatic cross-sections, use Part::Section:
import FreeCAD as App
import Part

doc = App.newDocument()
shape = doc.addObject("Part::Box", "Box")
shape.Length = 30; shape.Width = 20; shape.Height = 20
doc.recompute()

# Section at Z=10
plane = Part.makePlane(60, 60, App.Vector(-15, -10, 10))
wire = shape.Shape.section(plane)
feat = doc.addObject("Part::Feature", "SectionAtZ10")
feat.Shape = wire
doc.recompute()