MeshDataTool does not calculate all Normals correctly

[anose001]

Your Godot version:
4.2 Mono
Issue description:
I followed the tutorials on generating an ArrayMesh and using MeshDataTool to update the normals of a displaced mesh. My understanding is that MeshDataTool should help in calculating normals of a modified mesh. However, it seems that even in this tutorial demo there is a visible seam that extends from the positive y-axis to the negative y-axis, see picture attached. Display Wireframe and Display Unshaded do not show any issues so I figured the normals along that seem are off.
Any ideas on how to fix this issue?

Is this even a documentation issue or more of a godot engine issue?

URL to the documentation page:
ArrayMesh
MeshDataTool

[clayjohn]

Any ideas on how to fix this issue?

It depends on what you are doing to generate the normals.

Is this even a documentation issue or more of a godot engine issue?

Neither ArrayMesh nor MeshDataTool will generate normals for you, so its not an engine issue. The MeshDataTool doc does include a cheap example to generate normals in some cases, but it explicitly says that the normals will be incorrect, so I wouldn't count on it in your actual project.

In particular the problem with the code example in the doc is that it doesn't clear the vertex normals to 0 before calculating the new normals. So instead of averaging all the neighbouring face normals (the correct thing), you average the neighbouring face normals with the old vertex normal.