When a polygon is missing on a 3D Mesh imported in Unreal Engine, and there is no issue with Nanite or automatic LOD generation, it might be a problem with faces normal orientation (faces are, in fact, inverted and point inwards instead of outwards). Here’s how to fix it:
- In Blender, show the [ ] Face Orientation overlay from the Show Overlay menu in the Topbar. (Screenshot 1);
Blue faces have a correct orientation while red faces are incorrect; - Switch to the Edit mode, and select each face in red;
- From the Topbar, go to Mesh ➤ Normals ➤ Flip (shortcut Alt + N);
- Make sure everything is blue, then export (shortcut F4).
Hope it helps!
Screenshot 1
