Some mesh operations cannot be performed in Blender if the mesh is non-manifold. To view the non-manifold elements of the mesh:
- Switch to
Edit Mode. The number of non-manifold elements in the mesh can be seen at the top where the number of vertices, edges and faces is displayed. For example, a non-manifold mesh of 14 faces, where 2 faces are non-manifold would be shown as
Strangely, Blender only displays and selects the non-manifold elements in Vertex or Edge select modes. It does not work in Face select mode. So, choose either the
Vertex select modeor the
Edge select mode. Next, choose Select > Non Manifold. You can also do this by pressing
Shift-Ctrl-Alt-M. The non-manifold vertices or edges are now displayed in orange and are selected for use in further operations.
Tried with: Blender 2.62 and Ubuntu 12.04 LTS