title: Three.js Updating mesh of TubeGeometry object
body: <p>I'm trying to create an tube and ability to interact with that tube like dragging mouse to change the start point/end point of the tube .For that I modify directly vertices position values and I would like update object in the scene</p>
  
  <p>However, I've struck a problem with the tube object I'm using: when I update the path points the mesh object doesn't update on the screen, so it seems like I can't modify it after it's been created.</p>
  
  <p>My 3d object creation is roughly like this:</p>
  
  <pre><code>var curve = new THREE.SplineCurve3([new THREE.Vector3(x, y, z), new THREE.Vector3(x2, y2, z2)]);
  var geometry = new THREE.TubeGeometry(curve, segments, 2, radiusSegments, closed);
  geometry.dynamic = true;
  var tubeMesh = THREE.SceneUtils.createMultiMaterialObject(geometry, [new THREE.MeshBasicMaterial({color: 0xffffff, opacity: 1, transparent: true})]);
  scene.add(tubeMesh);    
  </code></pre>
  
  <p>And when I want to update the points. I'm doing it like this:</p>
  
  <pre><code>tubeMesh.children[0].geometry.path.points[0] = new THREE.Vector3(x4, y4, z4));
  tubeMesh.children[0].geometry.path.points[1] = new THREE.Vector3(x3, y3, z3));
  tubeMesh.children[0].geometry.verticesNeedUpdate = true;
  </code></pre>
  
  <p>However, when I make changes the object doesn't seem to update on screen. Is it possible to do this with a Tube?</p>