two-link with Object3D

two link arm with object 3D grouping

HTML

<div id="info">two-link arm with end effector</div>
<script src="//cdnjs.cloudflare.com/ajax/libs/three.js/r70/three.min.js"></script>
<script src="https://dl.dropboxusercontent.com/u/3587259/Code/Threejs/OrbitControls.js">


</script>

CSS

#info {
  position: absolute;
  top: 0px;
  width: 100%;
  padding: 10px;
  text-align: center;
  color: #ffff00
}

JavaScript

var camera, scene, renderer, light, controls;
var arm, arm2;
var angle = 0;
var endEffector;

init();
animate();

function init() {

  scene = new THREE.Scene();

  camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
  camera.position.z = 500;
  scene.add(camera);

  arm = new THREE.Object3D();
  scene.add(arm);

  endEffector = new THREE.Mesh(new THREE.SphereGeometry(5, 10, 10),
    new THREE.MeshLambertMaterial({
      color: 0xff1234
    }));
  scene.add(endEffector);

  var mesh = new THREE.Mesh(new THREE.BoxGeometry(20, 5, 5),
    new THREE.MeshLambertMaterial());
  mesh.position.set(10, 2.5, 0);
  arm.add(mesh);

  arm2 = arm.clone();
  arm.add(arm2);

  console.log(arm2);

  light = new THREE.PointLight(0xffffff);
  light.position.set(100, 300, 200);
  scene.add(light);

  var gridXZ = new THREE.GridHelper(100, 10);
  gridXZ.setColors(new THREE.Color(0xff0000), new THREE.Color(0xffffff));
  scene.add(gridXZ);

  renderer = new THREE.WebGLRenderer();
  renderer.setSize(window.innerWidth, window.innerHeight);
  renderer.setClearColor(0x888888);

  controls = new THREE.OrbitControls(camera, renderer.domElement);

  document.body.appendChild(renderer.domElement);

}

function animate() {

  var eepos = arm2.children[0].localToWorld(new THREE.Vector3(12, 0, 0));
  endEffector.position.copy(eepos);

  controls.update();
  requestAnimationFrame(animate);
  render();
}

function render() {
  angle += 0.02;
  arm2.position.set(20, 0, 0);
  arm2.rotation.y = angle;

  arm.rotation.y = angle;

  renderer.render(scene, camera);
}