微信小程序之threejs全景

最近在开发小程序，身心疲惫，原因是功能和app相同，我裂开了。

各种封装组件，各种写页面，不过有个好处是以前写的h5拿来改一下标签，基本上还是ok的，就剩下最后几个功能，其中就有一个VR全景功能。

移动端倒是好做，上次做了大概2天就搞定了，原理就是threejs用css3做图片的旋转，具体例子可以参照https://threejs.org/examples/css3d_panorama.html不过多描述，下面进入今天的主角：在微信小程序中使用threejs实现VR全景功能。

刚开始想到这个功能，我是拒绝的，这简直就是要了我的头发啊，没办法，谁叫我走上开发这条不归路呢，自己选的路，秃头也要走完。。

那就硬着头皮开始吧，先百度搜了一下在小程序中使用threejs，找到一篇比较干货的文章https://developers.weixin.qq.com/community/develop/article/doc/00066c4b230b085051592292f5bc13，这篇文章作者把threejs给提炼出来了一个小程序版本，

照着他的demo先把canvas给搞出来先。然后再实现全景，怎么实现也是头疼的事情，怎么，我不会写，还不会改吗？

先看看以前h5的实现方式，采用CSS3DRenderer来实现，问题来了，小程序里面不支持dom的createElement，那咋整嘛，只有换思路了，继续研究threejs的demo，第一个版本思路出来了，说了太多废话，直接来代码了：

<view style="height: 100%; width: 100%;">
  <canvas type="webgl" id="c" style="width: 100%; height:100%;" bindtouchstart="touchStart" bindtouchmove="touchMove" bindtouchend="touchEnd" bindtouchcancel="touchCancel" bindlongtap="longTap" bindtap="tap"></canvas>
</view>

import * as THREE from '../../lib/threejs/three.weapp.min.js'
import { OrbitControls } from '../../lib/threejs/OrbitControls'

Page({
  data: {},
  onLoad: function () {
    wx.createSelectorQuery()
      .select('#c')
      .node()
      .exec((res) => {
        // 创建canvas对象
        const canvas = THREE.global.registerCanvas(res[0].node)
        // 记录canvas的id，好在page销毁的时候释放canvas
        this.setData({ canvasId: canvas._canvasId })

        const camera = new THREE.PerspectiveCamera(75, canvas.width / canvas.height, 1, 2000);
        camera.position.z = 500;
        const scene = new THREE.Scene();
        scene.background = new THREE.Color(0xAAAAAA);
        const renderer = new THREE.WebGLRenderer({ antialias: true });
      
        const controls = new OrbitControls(camera, renderer.domElement);
 
        camera.position.set(200, 200, 500);
        controls.update();
        const geometry = new THREE.SphereBufferGeometry( 500, 60, 40 ).toNonIndexed();
        geometry.scale( - 1, 1, 1 );

        var texture = new THREE.TextureLoader().load( 'http://www.yanhuangxueyuan.com/threejs/examples/textures/2294472375_24a3b8ef46_o.jpg' ); // canvas中文文档作者的图，侵删
        texture.minFilter = THREE.LinearFilter;
        texture.format = THREE.RGBFormat;
        var material = new THREE.MeshBasicMaterial( { map: texture } );
        const mesh = new THREE.Mesh(geometry, material);
        scene.add(mesh);
      
      
        function onWindowResize() {
          camera.aspect = window.innerWidth / window.innerHeight;
          camera.updateProjectionMatrix();
          renderer.setSize(canvas.width, canvas.height);
        }
        function render() {
          canvas.requestAnimationFrame(render);
          controls.update();
          renderer.render(scene, camera);
        }

        render()

      })
  },
  onUnload: function () {
    //  释放canvas
    THREE.global.unregisterCanvas(this.data.canvasId)
  },
  touchStart(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchstart')(e)
  },
  touchMove(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchmove')(e)
  },
  touchEnd(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchend')(e)
  }
})

嗨呀，以上代码我是看都看不懂，那咋办嘛，你挑的嘛偶像。莫有办法，只有百度查具体每个关键字的意思，这里也就不多讲了，因为我也不知道。这种方法有个问题就是，图片只支持一张的图片，而且这个图片是要用全景相机照出来的，限制比较多，怎么办嘛，肯定不能用这个方法呀，不然这个成本就没法估算了。

于是乎我开始探索第二种方法，还是采用6张图的方法，还是原来的配方，还是熟悉的味道。话不多少，上代码：

import * as THREE from './three.weapp.min.js'
import { OrbitControls } from './OrbitControls'

Page({
  data: {},
  onLoad: function () {
    wx.createSelectorQuery()
      .select('#c')
      .node()
      .exec((res) => {
        const canvas = THREE.global.registerCanvas(res[0].node)
        
        this.setData({ canvasId: canvas._canvasId })

        const camera = new THREE.PerspectiveCamera(75, canvas.width / canvas.height, 1, 2000);
        const scene = new THREE.Scene();
        const renderer = new THREE.WebGLRenderer({ antialias: true });
      
        const controls = new OrbitControls(camera, renderer.domElement);
        // 控制镜头缩放，这里禁用了，因为是用正方体做的 除非能解决正方体的大小问题
        controls.enableZoom = false
        camera.position.set(-0.1, 2, -5);
        controls.update();

        var sides = ['右.jpg', '左.jpg','上.jpg', '下.jpg','前.jpg', '后.jpg']
        var materials = [];
        for (var i = 0; i < sides.length; i++) {
          var side = sides[i];
          var texture = new THREE.TextureLoader().load(side);
          materials.push( new THREE.MeshBasicMaterial( { map: texture } ) );
        }
　　　　　// 这里物体的长宽高，我始终不知道该是多少
        var mesh = new THREE.Mesh( new THREE.BoxBufferGeometry( canvas.height, canvas.height, canvas.height ), materials );
        mesh.geometry.scale( -1, 1, 1 );

        scene.add(mesh);
      
      
        function onWindowResize() {
          camera.aspect = window.innerWidth / window.innerHeight;
          camera.updateProjectionMatrix();
          renderer.setSize(canvas.width, canvas.height);
        }
        function render() {
          canvas.requestAnimationFrame(render);
          controls.update();
          renderer.render(scene, camera);
        }

        render()

        
      })
  },
  onUnload: function () {
    THREE.global.unregisterCanvas(this.data.canvasId)
  },
  touchStart(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchstart')(e)
  },
  touchMove(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchmove')(e)
  },
  touchEnd(e) {
    console.log('canvas', e)
    THREE.global.touchEventHandlerFactory('canvas', 'touchend')(e)
  }
})