How to get the true size of the object

Questions
1

100% scale

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10% scale

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How to get the true size of the object
like this

i use

   let box:any = new THREE.Box3().setFromObject( object );
   let size = new THREE.Vector3();

The results were inaccurate in several of the above cases

The object could be a group or a mesh.

2

i think you need to call parent.updateWorldMatrix(true, true) before you Box3().setFromObject

3

i add
scene.updateMatrixWorld(true); scene.updateWorldMatrix(true, true);
It still doesn’t seem to work