A mon-manifold mesh contains geometry that cannot exist in the real world. Sometimes meshes (especially downloaded from the internet) can be invalid due to disconnected faces/edges/verticies, internal faces, or inconsistent winding order. mslicer is not currently able to handle these kinds of invalid meshes and may produce unexpected results when sliced.

Example

In this model, some triangles have a reverse winding order (colored gray) which causes the slicer to give an incorrect output as if those faces are completely ignored.

Repair Tools

Below are a some mesh processing tools that can repair non-manifold or invalid meshes. I have generally had better luck with the paid tools (they have free trials), but you will need to experiment a bit to see which tools are able to fix your specific mesh.

Paid

• Mesh Inspector
• Mathematica (RepairMesh function)

Free

• MeshLab
• Mesh Repair Tools (Blender Addon)
• Runebrace