Show Normals draws short lines along the normals of a mesh or a point cloud, that is, the directions in which the surface faces. Use it to check that the normals point outward, for example after scanning or repair: many tools rely on it, such as the Rays method of Measure Thickness. Select one mesh or one point cloud and click Inspect › Show Normals. The lines are drawn only while the tool is open: close the panel or click the button again to hide them. The object itself is not changed.
Find Flipped Normals
- Select the mesh and click Inspect › Show Normals. Show all is on, so a line is drawn from every vertex.
- Change Length if the lines are too short or too long to see. It changes only the display.
- Look for areas without lines. There the normals point into the model, and you see the back side of the triangles, drawn in a different color.
- Fix the orientation with Orient Mesh Normals (Mesh Repair › Orient Mesh Normals), which flips the components that look the wrong way, or with Flip Normals. To select the triangles that look the wrong way, use Select Disorientations.
Point Clouds
For a point cloud, the tool shows the normals stored in the cloud, one line per point. If the cloud has no normals, the button is unavailable with the message "Point cloud should have normals". Create them with Make Normals (Points › Make Normals), and make their directions consistent with Orient Point Normals or turn them all around with Flip Normals.
Kinds of Normals
| What is drawn | When | How it is computed |
|---|---|---|
| Vertex normals | A mesh, Pseudo normals off (default) | One per vertex, from the areas of the triangles around it |
| Pseudo normals | A mesh, Pseudo normals on | At a vertex: the average of the normals of the triangles around it, weighted by their angles at the vertex. At an edge: the average of the two triangle normals. On a face: the triangle normal |
| Point normals | A point cloud | The normals stored in the cloud |
Inspect One Vertex, Edge or Face
Turn off Show all to see the normal of one element:
- Click the model, or type a number in Picked vertId. A number that does not exist shows nothing, as the panel note "Invalid ids will not be visualized" says.
- Show neighbors also draws the normals of the vertices around the picked one. It is available only when Pseudo normals is off.
Pseudo Mode
With Pseudo normals on and Show all off, Pseudo Mode sets what you pick: Vert, Edge or Face. A click picks the nearest vertex, the nearest edge or the triangle under the cursor, and the number field becomes Picked vertId, Picked edgeId or Picked faceId.
Length sets the length of the lines in scene units. It starts at 0.8% of the diagonal of the object's bounding box and keeps your last value while it fits the object.
