Threejs实现宇宙中地球动态展示和卫星绕地运动

/**
 * 星星粒子
 */
function stars() {
  var starsGeometry = new THREE.Geometry();
  for (var i = 0; i < 3000; i++) {
    var starVector = new THREE.Vector3(
      THREE.Math.randFloatSpread(4000),
      THREE.Math.randFloatSpread(3000),
      THREE.Math.randFloatSpread(4000)
    );
    starsGeometry.vertices.push(starVector);
    starsGeometry.name = "starsGeometry" + i;
  }
  var starsMaterial = new THREE.PointsMaterial({
    color: 0x888888,
    sizeAttenuation: false
  })
  var starsPoint = new THREE.Points(starsGeometry, starsMaterial);
  starsPoint.name = "starsPoint";
  group.add(starsPoint);
}

/**
 * 返回行星轨道的组合体
 * @param starLiteSize 行星的大小
 * @param starLiteRadius 行星的旋转半径
 * @param rotation 行星组合体的x,y,z三个方向的旋转角度
 * @param speed 行星运动速度
 * @param imgUrl 行星的贴图
 * @param scene 场景
 * @returns {{satellite: THREE.Mesh, speed: *}} 卫星组合对象;速度
 */
var initSatellite = function(starLiteSize, starLiteRadius, rotation, speed, imgUrl, scene) {
  var track = new THREE.Mesh(new THREE.RingGeometry(starLiteRadius, starLiteRadius + 0.3, 200, 1),
    new THREE
    .MeshBasicMaterial());
  var centerMesh = new THREE.Mesh(new THREE.SphereGeometry(1, 1, 1), new THREE
    .MeshLambertMaterial()); //材质设定
  var starLite = new THREE.Sprite(new THREE.SpriteMaterial({
    map: THREE.ImageUtils.loadTexture(imgUrl)
  }));
  starLite.scale.x = starLite.scale.y = starLite.scale.z = starLiteSize;
  starLite.position.set(starLiteRadius, 0, 0);
  var pivotPoint = new THREE.Object3D();
  pivotPoint.add(starLite);
  pivotPoint.add(track);
  centerMesh.add(pivotPoint);
  centerMesh.rotation.set(-Math.PI * 0.45, Math.PI * 0.1, 0);
  scene.add(centerMesh);
  return {
    starLite: centerMesh,
    speed: speed
  };
}
// 地球卫星
starLites.push(initSatellite(10, 150, {
  x: 0,
  y: 0,
  z: 0
}, 0.01, 'assets/earth/satellite.png', scene));