title: Get rotation of two vectors
body: <p>How do you rotate an object given two vectors that it should be relative to?</p>
  
  <p>I tried to use quaternion, however it seems to be giving me incorrect result as shown below.</p>
  
  <pre><code>var quaternion = new THREE.Quaternion().setFromUnitVectors( (new THREE.Vector3( x1, y1, z1 )), (new THREE.Vector3( x2, y2, z2 )));
  quaternion.normalize();
  </code></pre>
  
  <p>Any help is kindly appreciated.</p>
  
  <p><img src="https://i.stack.imgur.com/E7JvA.png" alt="3D Preview"></p>