// 初始化场景
var scene = new THREE.Scene();
// 初始化相机，第一个参数为摄像机视锥体垂直视野角度，第二个参数为摄像机视锥体长宽比，
// 第三个参数为摄像机视锥体近端面，第四个参数为摄像机视锥体远端面
var camera = new THREE.PerspectiveCamera(20, dom.clientWidth / dom.clientHeight, 1, 100000);
// 设置相机位置，对应参数分别表示x，y，z位置
camera.position.set(0, 0, 500);
var renderer = new THREE.WebGLRenderer({
      alpha: true,
      antialias: true
});

// 设置窗口尺寸，第一个参数为宽度，第二个参数为高度
renderer.setSize(dom.clientWidth, dom.clientHeight);
// 初始化控制器
var orbitcontrols = new THREE.OrbitControls(camera,renderer.domElement);
// 将渲染器加载到dom中
dom.appendChild(renderer.domElement);

// 定义太阳材质
var sunTexture = THREE.ImageUtils.loadTexture('./image/sun_bg.jpg', {}, function () {
    renderer.render(scene, camera);
});
// 太阳以及太阳材质设定
centerBall = new THREE.Mesh(new THREE.SphereGeometry(30, 30, 30), new THREE.MeshBasicMaterial({
    map: sunTexture
}));
scene.add(centerBall);

/**
* 实现球体发光
* @param color 颜色的r,g和b值,比如：“123,123,123”;
* @returns {Element} 返回canvas对象
*/
var generateSprite = function (color) {
   var canvas = document.createElement('canvas');
   canvas.width = 16;
   canvas.height = 16;
   var context = canvas.getContext('2d');
   var gradient = context.createRadialGradient(canvas.width / 2, canvas.height / 2, 0, canvas.width / 2, 
   canvas.height / 2, canvas.width / 2);
   gradient.addColorStop(0, 'rgba(' + color + ',1)');
   gradient.addColorStop(0.2, 'rgba(' + color + ',1)');
   gradient.addColorStop(0.4, 'rgba(' + color + ',.6)');
   gradient.addColorStop(1, 'rgba(0,0,0,0)');
   context.fillStyle = gradient;
   context.fillRect(0, 0, canvas.width, canvas.height);
   return canvas;
};
// 添加太阳发光效果
var centerBallLite = new THREE.Sprite(new THREE.SpriteMaterial({
   map: new THREE.CanvasTexture(generateSprite(sunSpriteColor)),
   blending: THREE.AdditiveBlending
}));
centerBallLite.scale.x = centerBallLite.scale.y = centerBallLite.scale.z = sunScaleSize;
scene.add(centerBallLite);

/**
 * 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 + 0.05, 50, 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(rotation.x, rotation.y, rotation.z);
scene.add(centerMesh);
   return {starLite: centerMesh, speed: speed};
};

// 执行函数
var render = function () {
    renderer.render(scene, camera);
    centerBall.rotation.y -= 0.01;
    for (var i = 0; i < starLites.length; i++) {
        starLites[i].starLite.rotation.z -= starLites[i].speed;
    }
    orbitcontrols.update();
    requestAnimationFrame(render);
}