How to rotate sphere by 'grabbing' it?

Asking for help

by MichaelJendryke

HTML

<script src="http://threejs.org/build/three.min.js"></script>
<script src="http://threejs.org/examples/js/controls/OrbitControls.js"></script>

CSS

body {
	background-color: #000;
	margin: 0px;
	overflow: hidden;
}

JavaScript

var renderer, scene, camera, controls;

init();
animate();

function init() {

    // renderer
    renderer = new THREE.WebGLRenderer();
    renderer.setSize( window.innerWidth, window.innerHeight );
    document.body.appendChild( renderer.domElement );

    // scene
    scene = new THREE.Scene();
    
    // camera
    camera = new THREE.PerspectiveCamera( 40, window.innerWidth / window.innerHeight, 1, 1000 );
    camera.position.set( 20, 20, 20 );

    // controls
    controls = new THREE.OrbitControls( camera );
    
	var light = new THREE.HemisphereLight( 0xeeeeee, 0x888888, 1 );
	light.position.set( 0, 20, 0 );
	scene.add( light );
    
    // axes
    scene.add( new THREE.AxisHelper( 20 ) );

    // geometry
    var geometry = new THREE.SphereGeometry( 15, 42, 42);
    
    // material
    var material = new THREE.MeshPhongMaterial( {
        color: 0xff0000, 
        shading: THREE.FlatShading,
        polygonOffset: true,
        polygonOffsetFactor: 1, // positive value pushes polygon further away
        polygonOffsetUnits: 1
    } );
    
    // mesh
    var mesh = new THREE.Mesh( geometry, material );
    scene.add( mesh );

    // wireframe - new way
    var geo = new THREE.EdgesGeometry( mesh.geometry ); // or WireframeGeometry
    var mat = new THREE.LineBasicMaterial( { color: 0xffffff, linewidth: 2 } );
    var wireframe = new THREE.LineSegments( geo, mat );
    mesh.add( wireframe );

}

function animate() {

    requestAnimationFrame( animate );
    
    //controls.update();

    renderer.render( scene, camera );

}