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Cut Point Cloud

In one sentence: Draw a lasso polygon in the 3-D view to delete all points inside the selected region from a point cloud.

Overview

Workbench: Points
Menu: Points → Cut Point Cloud
Shortcut: none

Enters an interactive lasso-selection mode. You click to place polygon vertices in the 3-D view; when you close the polygon, all points that project inside the polygon from the current camera angle are removed from the cloud.

Intuition

Think of it as using scissors on a photograph of your cloud. You draw a closed outline around the region you want to remove, and everything inside the outline disappears. The "outline" is always projected from your current viewing angle, so rotating the view before cutting gives you control over which points are actually removed in 3-D.

When to use it

  • Removing ground points, walls, or background clutter from a scan before processing.
  • Isolating a region of interest by cutting away everything outside it.
  • Quickly cleaning obvious noise or erroneous returns from a cloud.

When NOT to use it

  • Don't use this for precise boundary extraction — the lasso projects from the current camera, so depth ambiguity means points "behind" the target may also be cut. Rotate and cut in multiple passes for precise results.
  • Don't expect undo — the cut modifies the in-memory cloud. Save a copy first if you need to recover the original points.

Step-by-step

  1. Select a Points::Feature object in the document tree.
  2. Choose Points → Cut Point Cloud.
  3. The cursor changes to a lasso cursor.
  4. Click in the 3-D view to place the first polygon vertex.
  5. Continue clicking to add more vertices around the region to cut.
  6. Double-click on the last vertex (or click the first vertex again) to close the polygon and confirm the cut.
  7. Points inside the lasso are deleted from the cloud.
  8. Press Escape at any time before closing the polygon to cancel.

Tip

Rotate to a viewpoint where the target region is clearly separated in screen space before drawing the lasso. For clouds with depth complexity, make multiple passes from different angles.

Parameters

This tool has no parameters — it is entirely interactive.

Common mistakes and pitfalls

Wrong points removed due to depth projection

Cause: The lasso projects from the camera. Points that appear inside the polygon on-screen may be at different depths — both a near and a far cluster inside the projected outline will be cut.
Fix: Rotate to a view that separates the target depth plane. Use multiple lasso cuts from different angles if the cloud has overlapping regions of interest.

Cut is non-reversible

Cause: The tool deletes points from the in-memory kernel with no undo stack.
Fix: Before cutting, duplicate the cloud (select it and use Edit → Duplicate) or export it with Export Points to preserve the original.

Lasso does not close correctly

Cause: Clicking outside the 3-D viewport or hitting the wrong key may dismiss the lasso tool without cutting.
Fix: Double-click the last vertex while the cursor is in the 3-D viewport to close the lasso.

Python API

The Cut Point Cloud tool is interactive-only and does not have a direct Python equivalent. For scripted removal of points, manipulate the point kernel directly:

import FreeCAD as App

doc = App.ActiveDocument
cloud = doc.getObject("PointsFeature")
kernel = cloud.Points.getValue()

# Keep only points above Z = 0 (example filter)
kept = [kernel.getPoint(i) for i in range(kernel.size())
        if kernel.getPoint(i).z > 0]

# Write the filtered cloud back
import Points as Pts
new_cloud = doc.addObject("Points::Feature", "FilteredCloud")
new_kernel = Pts.Points()
for pt in kept:
    new_kernel.addPoint(pt)
new_cloud.Points = new_kernel
doc.recompute()

See also