Editor: Add center option.

[Mugen87]

Related issue: -

Description

This PR adds a center option in the Edit menu bar in the editor. It makes it possible to center objects which is useful for debugging models.

[mrdoob]

Thanks!

[mrdoob]

I'm doing some clean up in the editor menu...

I forgot, what does this exactly center?

If I add a TorusKnot to the scene and I do edit/center it moves it to the left.
If I do edit/center again it moves it to the left again... 🤔

[Mugen87]

Sometimes the geometry data of meshes have an offset. So even if the position says (0,0,0), the mesh isn't located at the origin. The logic I have added at that time was from Don's glTF viewer which is executed once after the load of an glTF asset.

I think the issue in the editor can be fixed by rewriting the code to:

newPosition.x = object.position.x - center.x;
newPosition.y = object.position.y - center.y;
newPosition.z = object.position.z - center.z;

/cc @donmccurdy

[donmccurdy]

That's cleaner yes, thanks! Fixed donmccurdy/three-gltf-viewer@202edc1.