three.js testbed

with orbitControls, XZgrid, info

by YouTingKuo

HTML

<div id="info">Ball Trails
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r78/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/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, controls;
var pos, vel, force;
var clock = new THREE.Clock();
var ballArray = [];
var rot = 0;

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 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);

	////////////////////////////////////////////////////////////////////////
  pos = new THREE.Vector3(-80, 0, 0);
  vel = new THREE.Vector3(30, 120, 0);
  force = new THREE.Vector3(0, -40, 0);
}

function makeBall() {
	THREE.ImageUtils.crossOrigin = '';
  var texture =
  THREE.ImageUtils.loadTexture('https://i.imgur.com/vSpU7ik.png');
  var geometry = new THREE.SphereGeometry(5, 20, 20);
  var material = new THREE.MeshBasicMaterial({map: texture, 
                         transparent: true, 
                         side:THREE.DoubleSide});
	
  
  
  var ball = new THREE.Mesh(geometry, material);
  return ball;
}

function ballUpdate(dt) {
  vel.add(force.clone().multiplyScalar(dt));
  pos.add(vel.clone().multiplyScalar(dt));

  var ballc = makeBall();
  ballc.position.copy(pos);
  ballc.rotation.y = rot;
  ballc.rotation.z = rot + 1.5;
  rot += 0.3; 
  scene.add(ballc);
  ballArray.push(ballc);
}

function animate() {
  if (pos.y >= 0) {
    var dt = 0.4;   // 大一點的dt 不會那麼密
    //var dt = clock.getDelta();
    ballUpdate(dt);
  }

  // process ball transparency
  var n = ballArray.length;
  var opacity = 1;
  for (i = n - 1; i >= 0; i--) {
    // console.log(i + ': ' + opacity);
    ballArray[i].material.opacity = opacity > 0 ? opacity : 1;
    opacity -= 0.01;  // 遞減
  }

  controls.update();

 ...