Unable to get bounding box for 2D element in IOS UIWebView Forge viewer

I have used below code to get bounding box of 2D element.

function find2DBounds( fragList, fragId, dbId, bc ) {
    const mesh = fragList.getVizmesh( fragId );
    const vbr = new Autodesk.Viewing.Private.VertexBufferReader( mesh.geometry );
    vbr.enumGeomsForObject( dbId, bc );

function get2DBounds( dbId, model ) {
    const it = model.getData().instanceTree;
    const fragList = model.getFragmentList();

    let bounds = new THREE.Box3();
    let bc = new Autodesk.Viewing.Private.BoundsCallback( bounds );
    const dbId2fragId = model.getData().fragments.dbId2fragId;
    const fragIds = dbId2fragId[dbId];

    if( Array.isArray( fragIds ) ) {
        for( let i = 0; i < fragIds.length; i++ ) {
            find2DBounds( fragList, fragIds[i], dbId, bc );
    } else if( typeof fragIds === 'number' ) {
        find2DBounds( fragList, fragIds, dbId, bc );

    return bc.bounds;

var model = this.viewer.model; 
 var modelData = model.getData();
 var itree = modelData.instanceTree;
itree.enumNodeChildren(itree.getRootId(), function (dbId) {   
// Here you go
cosnt bondingBox = get2DBounds( dbId, viewer.model );


This code is correctly in browser and getting correct bounding box for 2D elements.
But when I tried to execute this code in browser through IOS, I am not getting bounding box for 2D elements.

Process of use above code through IOS :
– Design a UIWebView in IOS
– Embed html page
– Embed above java script code to into html page
– Get all element ids for 2D sheet.
– Get bounding box for those using above code.

observed that bounding box are infinity for all 2D entities.

Could you please tell me what is wrong with these approach?

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