onMaterialsLoaded = function ( materials ) {
			if ( materials !== null ) scope.meshBuilder.setMaterials( materials );
			scope._loadObj( available.obj, scope.callbacks.onLoad, null, null, scope.callbacks.onMeshAlter, prepData.useAsync );

		}
Run the loader according the provided instructions.

@param {THREE.LoaderSupport.PrepData} prepData All parameters and resources required for execution
@param {THREE.LoaderSupport.WorkerSupport} [workerSupportExternal] Use pre-existing WorkerSupport