object3d.matrix

by Rebecca Chen

HTML

<div id="info">Using matrix in Object3D
  <script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r78/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
}

body {
  overflow: hidden;
}

JavaScript

var camera, scene, renderer, mesh, controls;
var angle = 0;
var clock = new THREE.Clock();
var pos = new THREE.Vector3();

init();
animate();

function init() {
  scene = new THREE.Scene();

  camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 1000);
  camera.position.z = 500;
  scene.add(camera);

  var geometry = new THREE.BoxGeometry(24, 6, 12);
  var material = new THREE.MeshNormalMaterial();

  mesh = new THREE.Mesh(geometry, material);
  scene.add(mesh);

  var gridXZ = new THREE.GridHelper(100, 10, 'red', 'white');
  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() {
  controls.update();
	var dt = clock.getDelta();
  var omega = 2;
	angle += omega*dt;
 	pos.set (70*Math.cos(angle), 0, -70*Math.sin(angle));
  
  // directly set the 'matrix'
  var localX = new THREE.Vector3();
  var localY = new THREE.Vector3(0,1,0);
  var localZ = new THREE.Vector3();
  localX.set (-70*omega*Math.sin(angle), 0, -70*omega*Math.cos(angle)).normalize();
  localZ.crossVectors (localX, localY);

	mesh.matrix.makeBasis (localX, localY, localZ);
  mesh.matrix.setPosition (pos);

  mesh.matrixAutoUpdate = false;

	// setting the 'convenience properties'
  mesh.position.copy (pos);
  mesh.rotation.y = angle+Math.PI/2;

  requestAnimationFrame(animate);
  render();
}

function render() {
  renderer.render(scene, camera);
}