title: I can't get position attribute off a bufferGeometry
body: <p>I've got a line "walking around my scene" (some kind of a 3D snake) randomly and the next thing I wish to achieve is set a box around its head.
  The line <code>bufferGeometry</code> is set by  </p>
  
  <pre><code>        var positions1 = new Float32Array( MAX_POINTS * 3 ); // 3 vertices per point
          var positions2 = new Float32Array( MAX_POINTS * 3 ); // 3 vertices per point
          buffGeometry1.addAttribute( 'position', new THREE.BufferAttribute( positions1, 3 ) );
          buffGeometry2.addAttribute( 'position', new THREE.BufferAttribute( positions2, 3 ) );
  </code></pre>
  
  <p>I chose to set a cube (<code>boxGeometry</code> object) around it, and I used the following code lines to try and achieve that:</p>
  
  <pre><code>            var positioning = buffGeometry1.getAttribute('position');
              cube.position.x = positioning[0];//(line1.geometry.attributes.position.array[drawCount]);
              cube.position.y = positioning[1];//(line1.geometry.attributes.position.array[drawCount + 1]);
              cube.position.z = positioning[2];
  </code></pre>
  
  <p>As I debug, I see that my <code>positioning</code> array is undefined. so I guess something there went wrong.</p>
  
  <p>Thanks.</p>