> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Input Mesh must be Manifold

## Issue:

![An error message stating that the input mesh must be manifold](https://files.learn.ntop.com/help-articles/meshing-workflows/360084383173.png)

I'm trying to create a Quad Mesh, but I keep getting the error: "Input mesh must be manifold."

## Applies to:

* Quad Meshing
* Export to CAD
* Mesh export

## Cause:

#### **What is Manifold?**

A topological space that resembles Euclidean space up close. For example, the Earth looks like a plane when you are standing on the surface but from far away it is actually spherical. Manifold objects are continuous without any beginning or end. An example of this is a sphere or a cube. A non-manifold object would be a Plane.

Non-manifold geometry can't exist in real life, which makes this error one we need to solve if we want to 3D print our part.

#### **Why would a mesh be non-manifold?**

A mesh can be non-manifold due to many reasons. Some of the most common occurrences are:

* An edge connected to more or less than two faces (including internal faces)
* Separate regions connected through a single vertex
* Loose geometry (discontinuous)
* Plane normals pointing in opposite directions for adjacent faces

#### **Check to see if your mesh is manifold**

To check if your mesh is manifold or not, click on the info (?) panel and go to Properties. There will be a property called Manifold. If it says False, then it is not manifold and if it says True, then it is.

![A mesh from implicit body properties panel with the manifold property highlighted](https://files.learn.ntop.com/help-articles/meshing-workflows/360084385953.png)

## Solution:

If your mesh isn't manifold, you need to refine your mesh further. This can include using blocks like **Remesh Surface**, **Refine Mesh**, **Simplify Mesh by Threshold**, **Simplify Mesh by Amount**, or editing the Adaptivity and Feature Size. Take a look at this [article](/help-articles/knowledge-base/meshing-workflows/methods-for-refining-meshes) for further methods and tips on refining meshes.

If your mesh is still non-manifold after trying these steps, you may have to go back to your original part in a different program and try cleaning it up. Sending it to another program like Magics for cleaning up may also be necessary.

If you are trying to create a Quad Mesh using the **Quadrangulate Mesh** block, you will always want to use one of the refinement blocks mentioned above. Inputting a **Mesh from Implicit Body** or **Mesh from CAD Body** block will most likely cause an error when used without a refinement step.

## Keywords:

*cad error mesh meshing export property quadrangulate quad refine simplify threshold amount vertex input must be manifold euclidean topological space false plane discontinuous normals*