hw1 break

Part 2'

by joe chan

HTML

<div id="info">hw1
  <br>Press space to stop</div>
<script src="https://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>
<script src="https://jyunming-chen.github.io/tutsplus/js/KeyboardState.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, controls;
var keyboard = new KeyboardState();
var cylinder;
var brakeOn = false;

var pos, vel, force;
var mass = 1;
var clock = new THREE.Clock();

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);

  // add my cylinder
  var geometry = new THREE.CylinderGeometry(5, 5, 2, 32);
  var material = new THREE.MeshNormalMaterial();
  cylinder = new THREE.Mesh(geometry, material);
  scene.add(cylinder);

  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);

  //////////////////////
  pos = new THREE.Vector3();
  vel = new THREE.Vector3();
  force = new THREE.Vector3();

  document.body.appendChild(renderer.domElement);
}


function computeForce() {
  // engine force
  if (brakeOn)
    force = new THREE.Vector3(0, 0, 0);
  else
    force = new THREE.Vector3(5, 0, 10);

  // resistance force
  var alpha = 0.50;
  force.add(vel.clone().multiplyScalar(-alpha));
}

function animate() {
  keyboard.update();
  if (keyboard.down("space")) {
    brakeOn = true;
  }

  computeForce();
  var dt = clock.getDelta(); // delta-time
  // vel = vel + force/mass * dt
  vel.add(force.clone().multiplyScalar(dt / mass));
  // pos = pos + vel * dt
  pos.add(vel.clone().multiplyScalar(dt));

  // copy to cylinder   
  cylinder.position.copy(pos);

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

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

// important to add this 
// in jsfiddle!
window.focus();