title: From boundingBoxHelper to BoxHelper
body: <p>in threejs r83, boundingBoxHelper has been deprecated, using BoxHelper instead. How do you get the box of the BoxHelper?</p>
  
  <pre><code>let boundingBox = new THREE.BoxHelper(mesh);
  myObj.size = bounding.box.getSize(); // error
  </code></pre>
  
  <p>thank you for your help!</p>