Как добавить физику объекту в three.js?

function init() {

	var info = document.createElement( 'div' );
	info.style.position = 'absolute';
	info.style.bottom = '10px';
	info.style.width = '100%';
	info.style.textAlign = 'center';
	info.innerHTML = '<strong>click</strong>: add cube, <strong>shift + click</strong>: remove cube';
	document.body.appendChild( info ); //



	camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 10000 );
	camera.position.set( 0, 900, 800 );
	camera.rotation.y = 200;
	camera.lookAt( new THREE.Vector3() );

	scene = new THREE.Scene();

	// roll-over helpers

	rollOverGeo = new THREE.BoxGeometry( 60, 20, 20 );
	rollOverMaterial = new THREE.MeshBasicMaterial( { color: 0xff0000, opacity: 0.5, transparent: true } );
	rollOverMesh = new THREE.Mesh( rollOverGeo, rollOverMaterial );
	scene.add( rollOverMesh );

	// cubes

	cubeGeo = new THREE.BoxGeometry( 60, 20, 20, 10, 10, 10 );

	// grid

	var size = 500, step = 20;

	var geometry = new THREE.Geometry();

	for ( var i = - size; i <= size; i += step ) {

		geometry.vertices.push( new THREE.Vector3( - size, 0, i ) );
		geometry.vertices.push( new THREE.Vector3(   size, 0, i ) );

		geometry.vertices.push( new THREE.Vector3( i, 0, - size ) );
		geometry.vertices.push( new THREE.Vector3( i, 0,   size ) );

	}

	var material = new THREE.LineBasicMaterial( { color: 0x000000, opacity: 0.2, transparent: true } );

	var line = new THREE.LineSegments( geometry, material );
	scene.add( line );

	//

	raycaster = new THREE.Raycaster();
	mouse = new THREE.Vector2();

	var geometry = new THREE.PlaneBufferGeometry( 1000, 1000 );
	geometry.rotateX( - Math.PI / 2 );

	plane = new THREE.Mesh( geometry, new THREE.MeshBasicMaterial( { visible: false } ) );
	scene.add( plane );

	objects.push( plane );

	// Lights

	var ambientLight = new THREE.AmbientLight( 0x606060 );
	scene.add( ambientLight );

	var directionalLight = new THREE.DirectionalLight( 0xffffff );
	directionalLight.position.set( 1, 0.75, 0.5 ).normalize();
	scene.add( directionalLight );

	renderer = new THREE.WebGLRenderer( { antialias: true } );
	renderer.setClearColor( 0xf0f0f0 );
	renderer.setPixelRatio( window.devicePixelRatio );
	renderer.setSize( window.innerWidth, window.innerHeight );
	document.body.appendChild( renderer.domElement );  // 

	document.addEventListener( 'mousemove', onDocumentMouseMove, false );
	document.addEventListener( 'mousedown', onDocumentMouseDown, false );
	document.addEventListener( 'keydown', onDocumentKeyDown, false );
	document.addEventListener( 'keyup', onDocumentKeyUp, false );

	// help event

	window.addEventListener( 'resize', onWindowResize, false );

}

function onWindowResize() {

	camera.aspect = window.innerWidth / window.innerHeight;
	camera.updateProjectionMatrix();

	renderer.setSize( window.innerWidth, window.innerHeight );

}

function onDocumentMouseMove( event ) {

	event.preventDefault();

	mouse.set( ( event.clientX / window.innerWidth ) * 2 - 1, - ( event.clientY / window.innerHeight ) * 2 + 1 );

	raycaster.setFromCamera( mouse, camera );

	var intersects = raycaster.intersectObjects( objects );

	if ( intersects.length > 0 ) {

		var intersect = intersects[ 0 ];

		rollOverMesh.position.copy( intersect.point ).add( intersect.face.normal );
		rollOverMesh.position.divideScalar( 20 ).floor().multiplyScalar( 20 ).addScalar( 10 );

	}

	render();

}

function onDocumentMouseDown( event ) {

	event.preventDefault();

	// cubeMaterial = new THREE.MeshLambertMaterial( { color: 0xe3ca18, map: new THREE.TextureLoader().load( userSetting.texture ) } );
	
	var cubeMaterial = []

	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color }) );
	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color }) );
	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color, map: new THREE.TextureLoader().load( (userSetting.texture || 'img/lego-2.png') ) }) ); // top 
	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color }) );
	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color }) );
	cubeMaterial.push( new THREE.MeshLambertMaterial({ color: userSetting.color }) );

	mouse.set( ( event.clientX / window.innerWidth ) * 2 - 1, - ( event.clientY / window.innerHeight ) * 2 + 1 );

	raycaster.setFromCamera( mouse, camera );

	var intersects = raycaster.intersectObjects( objects );

	if ( intersects.length > 0 ) {

		var intersect = intersects[ 0 ];

		// delete cube

		if ( isShiftDown ) {

			if ( intersect.object != plane ) {

				scene.remove( intersect.object );

				objects.splice( objects.indexOf( intersect.object ), 1 );

			}

		// create cube

		} else {

			var voxel = new THREE.Mesh( cubeGeo, cubeMaterial );
			voxel.position.copy( intersect.point ).add( intersect.face.normal );
			voxel.position.divideScalar( 20 ).floor().multiplyScalar( 20 ).addScalar( 10 );
			scene.add( voxel );

			objects.push( voxel );

		}

		render();

	}

}

function onDocumentKeyDown( event ) {

	switch( event.keyCode ) {

		case 16: isShiftDown = true; break;

	}

}

function onDocumentKeyUp( event ) {

	switch ( event.keyCode ) {

		case 16: isShiftDown = false; break;

	}

}

function render() {

	renderer.render( scene, camera );

}