C# mesh transform applied in both editor and play mode

I have written a C# script that transform all meshes under parent a transform, the goal being to project flat country maps onto a sphere. The script class has [ExecuteInEditMode] and I have an associated Editor class.

I loop over all children and this works fine in editor mode. I basically make a copy of the sharedMesh, then apply the transform, and set the new mesh on the meshFilter.

Code (CSharp):

1.  
2. Mesh mesh = Mesh.Instantiate(geoMeshObject.MeshFilter.sharedMesh);
3. MeshToSphere(mesh, Radius);
4. geoMeshObject.ClonedMesh = mesh;
5. geoMeshObject.MeshFilter.mesh = geoMeshObject.ClonedMesh;
6.  

However, when I go to play mode from the editor, the transform gets applied a second time to the meshes. Basically it appears the shareMesh I get in play mode in not the original one, but the already transformed one. I was more expecting the play mode to start from a clean environment.

What is the correct approach for this type of script that procedurally alter/transform meshes in editor mode? I feel I'm missing some basic understanding of how sharedMesh and mesh exist in editor and play mode.

Any help/guidance appreciated!

Note that CopyMesh uses:

Code (CSharp):

1.  
2. Mesh clonedMesh = Instantiate<Mesh>(originalMesh);
3.  

I also tried to manually copy the mesh (but same results)

Code (CSharp):

1.  
2. Mesh clonedMesh = new Mesh();
3. clonedMesh.name = "clone";
4. clonedMesh.vertices = originalMesh.vertices;
5. clonedMesh.triangles = originalMesh.triangles;
6. clonedMesh.normals = originalMesh.normals;
7. clonedMesh.uv = originalMesh.uv;
8.  

Script disabled in Editor


Scripts enabled in Editor



Double transform in Play Mode

 

I'm not super-fond of ExecuteInEdit mode generally, just because of this conflation of when things happen.

The approach I favor is a separate editor-only method that operates on the current

Selection

:

https://docs.unity3d.com/ScriptReference/Selection.html

You can conditionally compile editor code into your main game scripts with:

Code (csharp):

1. #if UNITY_EDITOR
2.   // code here that ONLY works in editor, will never build to target
3. #endif

And partial classes can even help keep it in another file entirely, to reduce clutter.