title: THREE.js lookAt - How to pan smoothly between old and new target positions?
body: <p><a href="http://jsfiddle.net/1dtx78bj/21/" rel="nofollow">Example JSfiddle</a></p>
  
  <p>I can get my cone to point at each target sphere in turn (red,green,yellow,blue) using the THREE.js  "lookAt" function.</p>
  
  <pre><code>// Initialisation
  
  c_geometry = new THREE.CylinderGeometry(3, 40, 120, 40, 10, false);
  c_geometry.applyMatrix( new THREE.Matrix4().makeRotationX( Math.PI / 2 ) );
  c_material = new THREE.MeshNormalMaterial()
  myCone = new THREE.Mesh(c_geometry, c_material);
  scene.add(myCone);
  
  // Application (within the Animation loop)
  
  myCone.lookAt(target.position); 
  </code></pre>
  
  <p>But now I want the cone to pan smoothly and slowly from the old target to the new target.  I guess that I can do it by computing intermediate points on the circular arc which is centred at the cone centre Cxyz and which passes from the previous target position Pxyz to the new target position Nxyz.</p>
  
  <p>Please can someone point me to suitable: (a) utilities or (b) trigonometry algorithms or (c) code examples for calculating the xyz coordinates of the intermediate points on such an arc? (I will supply the angular increment between points based on desired sweep rate and time interval between frames).</p>