How to Check a Model’s Normals in SketchUp
SketchUp is very intelligent. From a highly technical computer-science perspective, every face in your model has two sides: an inside and an outside. The two sides are set apart by a bit of data called the face’s normal.
SketchUp is smart enough that it doesn’t matter how the normals (also known as the front and back) are oriented; both sides are treated the same. 3D printers aren’t that clever; they need to have all the normals oriented so the outsides are pointing out and the insides are pointing in.
To check your model’s normals, you’ll need to look at it styled with SketchUp’s default texture. Choose View → Face Style → Monochrome to hide any colors or textures you’ve added to the model and see the default material.
Any faces that are shaded the default blue have reversed normals. These faces will need to be corrected, or the 3D printer will see them as missing.
- To correct a single face, context-click the face and select Reverse Faces from the menu that appears.
- To correct several misaligned faces, context-click one of the faces that is white and select Orient Faces. Doing so flips all the faces in the model.
If the Orient Faces tool causes everything to flip randomly, it’s a sign that you have extraneous faces inside your model. Use the Section Plane tool to look inside, find the face, and erase it.