Calculating zoom % for 3D files(OBJ,FBX,GLTF)

Questions
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1

Hi I want to know how can we calculate zoom % for 3 D files. I am using three react module and it has Orbitcontrols.

this.controls = new OrbitControls(this.camera, this.container);

I am able to get the distance from the camera for a 3 D object when I zoom in or zoom out by moving the mouse wheel in my application. I want to know how can we derive the zoom from the distance from the camera or do we have any other way to calculate zoom. Please see below piece of code and suggest.

this.container.addEventListener('wheel', this.handleMouseMove, false);

  handleMouseMove = () => {
         const dist = this.controls.target.distanceTo( this.controls.object.position )
 }
2

Please refer the following code:

    var zoom = 100; // Default 100%
    window.addEventListener( 'wheel', onDocumentMouseWheel, false );
    function onDocumentMouseWheel(event ) {
        if(event.deltaY > 0) {
            zoom = zoom *0.95;
        } else {
            zoom = zoom /0.95;
        }
        zoom = zoom? Math.floor(zoom) : 100;
        console.log(zoom, '%');
    }