world surface
  // and attempt to find a hit. `hitTest` returns an array of potential
  // hits.
  var hits = vrDisplay.hitTest(x, y);

  if (!model) {
    console.warn('Model not yet loaded');
    return;
  }

  // If a hit is found, just use the first one
  if (hits && hits.length) {
    var hit = hits[0];

    // Turn the model matrix from the VRHit into a
    // THREE.Matrix4 so we can extract the position
    // elements out so we can position the shadow mesh
    // to be directly under our model. This