title: Intersection within Object3D
body: <p>I have some objects added to an Object3D (for grouping elements) and I'm trying to detect clicks on it.
  My scene has a size of <code>600x400</code>, my camera is within a three-object and my event handler code looks like below:</p>
  
  <pre><code>function onDocumentMouseDown( event ) {
     event.preventDefault();
  
     var mouse = {};
     mouse.x = ( event.clientX / 600 ) * 2 - 1;
     mouse.y = - ( event.clientY / 400 ) * 2 + 1;
  
     var vector = new THREE.Vector3( mouse.x, mouse.y, 1 );
     projector.unprojectVector( vector, three.camera );
  
     var ray = new THREE.Ray( three.camera.position, vector.subSelf( three.camera.position ).normalize() );
  
     var intersects = ray.intersectObjects( group.children );
     alert(intersects.length);
     [...]
  }
  </code></pre>
  
  <p>Actually I'm alerting the count of intersected objects. But it stays zero. It couldn't find any intersected objects. I've already played a bit aroud with the x, y and z values of my projection vector - without success.</p>
  
  <p>I've added a stripped down sample for demonstrating this issue on <a href="http://jsfiddle.net/W9svk/">jsfiddle</a>. Maybe someone has a short hint for me what goes wrong with it?</p>