Orient Point Normals makes the existing normals of a point cloud face the same side as the normals of their neighbours. Use it when a cloud has normals, but in some areas they face outwards and in others inwards. You see it as patchy shading, with dark and light spots on a smooth surface, or in Inspect › Show Normals as lines that go into the object in some places.
This happens, for example:
- after Make Normals with Fast orientation on an object with deep hollows;
- with normals that came in the file from other software;
- in a cloud combined from several scans whose normals were made in different ways.
Orient Point Normals keeps the line of each normal and changes only its side. To compute completely new normals, use Make Normals instead. To reverse all normals at once, use Flip Normals.
How to orient point normals
- Select one or more point clouds in the Scene tree. Each of them must have normals; otherwise the button is unavailable and its tooltip says All selected objects must be point clouds with normals. A cloud without normals needs Make Normals first.
- Click Points › Orient Point Normals.
- If needed, change Nearest Neighbours.
- Click Run. MeshInspector orients the normals and closes the panel.
| Parameter | What it does | Default and tips |
|---|---|---|
| Nearest Neighbours | How many nearest points are used to build a small local triangulation around each point, to decide which normals are neighbours | 16, from 6 to 99. A too small value can give a poor local triangulation; a large value makes the tool slower |
If the result is not what you need, use Undo (Ctrl+Z, or Cmd+Z on macOS). If after it all normals of the cloud face inwards, reverse them with Flip Normals.
Fix only a selected area
If most normals of the cloud are right and only one area is wrong, select that area first:
- Select the wrong points with Points › Select Primitives.
- Click Points › Orient Point Normals and Run.
The normals of the unselected points stay as they are and serve as the reference: MeshInspector changes only the selected points, so that they face the same side as their unselected neighbours. Without a selection, the tool orients all points of the cloud. To clear the selection afterwards, use Points › Clear Selections.
Example: before and after
Before you run the tool, look at the current normals: keep the cloud selected and click Inspect › Show Normals.
The normals of this terrain scan appear as short white lines from the points:
Next, Orient Point Normals ran with Nearest Neighbours set to 30. To compare, turn on Show Normals again after the tool:
For the normals of a mesh, use Orient Mesh Normals on the Mesh Repair tab instead.
