Add subdivision to a geometry - three.js

Question

I'm trying add subdivisions to a sphere like this:
http://stemkoski.github.com/Three.js/Subdivision-Cube.html
Here's my code: http://jsfiddle.net/mdrorum/HvFLw/
<script src="http://mrdoob.github.com/three.js/build/three.js"></script>
<script type="text/javascript">
var camera, scene, renderer;
var geometry, material, mesh;
var smooth, subdiv, modifier;
init();
animate();
function init() {
camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.z = 1000;
scene = new THREE.Scene();
renderer = new THREE.CanvasRenderer();
renderer.setSize( window.innerWidth, window.innerHeight );
document.body.appendChild( renderer.domElement );
geometry = new THREE.SphereGeometry( 200 );
material = new THREE.MeshBasicMaterial( { color: 0x00ff00, wireframe: true } );
mesh = new THREE.Mesh( geometry, material );
scene.add( mesh );
var smooth = mesh.clone();
var subdiv = 3;
var modifier = new THREE.SubdivisionModifier( subdiv );
//modifier.modify( smooth );
}
function animate() {
requestAnimationFrame( animate );
mesh.rotation.x += 0.01;
mesh.rotation.y += 0.02;
renderer.render( scene, camera );
}
</script>
This works fine, but uncomment: //modifier.modify( smooth );
Nothing happens. :(
How I can add subdivisions?

Answer 1

Here you can find a good tutorial with a working demo. Citing the author:
// First we want to clone our original geometry.
// Just in case we want to get the low poly version back.
var smooth = THREE.GeometryUtils.clone( geometry );
// Next, we need to merge vertices to clean up any unwanted vertex.
smooth.mergeVertices();
// Create a new instance of the modifier and pass the number of divisions.
var divisions = 3;
var modifier = new THREE.SubdivisionModifier(divisions);
// Apply the modifier to our cloned geometry.
modifier.modify( smooth );
// Finally, add our new detailed geometry to a mesh object and add it to our scene.
var mesh = new THREE.Mesh( smooth, new THREE.MeshPhongMaterial( { color: 0x222222 } ) );
scene.add( mesh );

Answer 2

You are trying to modify a mesh. You need to modify a geometry.
modifier.modify( geometry );