利用 ThreeJS 实现动态围栏效果

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          <!doctype html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="initial-scale=1.0, user-scalable=no, width=device-width">
  <title>利用 ThreeJS 实现动态边界墙</title>
  <link rel="stylesheet" href="http://a.amap.com/jsapi_demos/static/demo-center/css/demo-center.css" />
  <style>
    html,
    body,
    #container {
      width: 100%;
      height: 100%;
    }
  </style>
</head>

<body>
<div id="container"></div>
<script>
  console.warn = console.log;

</script>
<script src="http://webapi.amap.com/maps?v=2.0&key=您申请的key值"></script>
<script src="https://cdn.jsdelivr.net/npm/three@0.142/build/three.js"></script>
<script src="https://cdn.jsdelivr.net/gh/mrdoob/three.js@master/examples/js/loaders/GLTFLoader.js">
</script>
<script>javascript: (function () { var script = document.createElement('script');
  script.onload = function () { var stats = new Stats(); document.body.appendChild(stats.dom);
    requestAnimationFrame(function loop() { stats.update(); requestAnimationFrame(loop) }); };
  script.src = 'https://mrdoob.github.io/stats.js/build/stats.min.js'; document.head.appendChild(script); })()
</script>

<script>

  const container = document.getElementById('container')

  const  map = new AMap.Map('container', {
    center: [116.52668, 39.794678],
    zooms: [2, 20],
    zoom: 17.5,
    viewMode: '3D',
    mapStyle: 'amap://styles/grey',
    pitch: 52,
  })


  map.on('click', (event) => {
    const {lng, lat} = event.lnglat
    console.log([lng, lat])
  })

  // 墙体路径原始数据
  const data = [
    [
      [116.523344, 39.795124],
      [116.526568, 39.796617],
      [116.528888, 39.793540],
      [116.525796, 39.792064],
      [116.523344, 39.795124],
    ]
  ]
  // 地理坐标转为three坐标系，不管用不用arr，都需要转换一个非空数组
  // 否则customCoords没实例化api会报错
  const paths = map.customCoords.lngLatsToCoords(data)

  // 墙体高度
  const height = 50
  // 墙体颜色
  const color = '#FFD500'
  // 动效纹理
  let texture = null
  // 动效纹理偏移
  let texture_offset = 0

  // THREE相关变量
  let camera, scene, renderer

  // 初始化图层
  function initLayer () {

    const layer = new AMap.GLCustomLayer({
      zIndex: 9999,
      visible: true,
      init: (gl) => {
        initThree(gl)
        createWall()
        animate()
      },
      render: () => {

        const { near, far, fov, up, lookAt, position } = map.customCoords.getCameraParams()

        camera.near = near// 近平面
        camera.far = far // 远平面
        camera.fov = fov // 视野范围
        camera.position.set(...position)
        camera.up.set(...up)
        camera.lookAt(...lookAt)

        // 更新相机坐标系
        camera.updateProjectionMatrix()

        renderer.render(scene, camera)

        // 这里必须执行！重新设置 three 的 gl 上下文状态
        renderer.resetState()
      }
    })

    map.add(layer)
  }


  function initThree (gl) {
    camera = new THREE.PerspectiveCamera(60, container.clientWidth / container.clientHeight, 100, 1 << 30)
    renderer = new THREE.WebGLRenderer({
      context: gl,
      // canvas: document.querySelector('.amap-layer'), //也可以直接用canvas初始化
      antialias: true // 抗锯齿，默认false 耗性能
    })
    // 自动清空画布这里必须设置为 false，否则地图底图将无法显示
    renderer.autoClear = false
    renderer.outputEncoding = THREE.sRGBEncoding

    scene = new THREE.Scene()
    // 增加环境光
    const aLight = new THREE.AmbientLight(0xffffff, 0.3)
    scene.add(aLight)
  }


  function createCube () {
    const geometry = new THREE.BoxGeometry(200, 200, 200)
    const material = new THREE.MeshBasicMaterial({
      color: 0xffffff,
      side: THREE.DoubleSide,
      transparent: true,
      depthWrite: false
    })
    const cube = new THREE.Mesh(geometry, material)
    cube.position.set(0, 0, 0)
    scene.add(cube)
  }

  function createWall () {

    let faceList = []
    let faceVertexUvs = []

    // 合并多个闭合范围
    for (let i = 0; i < paths.length; i++) {
      const { face, uvs } = generateVecData(paths[i])
      faceList = [...faceList, ...face]
      faceVertexUvs = [...faceVertexUvs, ...uvs]
    }

    // 背景层
    const geometry = new THREE.BufferGeometry()
    geometry.setAttribute('position', new THREE.BufferAttribute(new Float32Array(faceList), 3))
    geometry.setAttribute('uv', new THREE.BufferAttribute(new Float32Array(faceVertexUvs), 2))

    const material1 = new THREE.MeshBasicMaterial({
      color: color,
      side: THREE.DoubleSide,
      transparent: true,
      depthWrite: false,
      alphaMap: new THREE.TextureLoader().load('./images/texture_1.png'), // 不透明图片
      // wireframe: true
    })
    const mesh1 = new THREE.Mesh(geometry, material1)
    scene.add(mesh1)

    // 动画层
    const geometry2 = geometry.clone()
    texture = this.generateTexture(128, color)
    texture.wrapS = THREE.RepeatWrapping // 水平重复平铺
    texture.wrapT = THREE.RepeatWrapping // 垂直重复平铺

    const material2 = new THREE.MeshBasicMaterial({
      side: THREE.DoubleSide,
      transparent: true,
      depthWrite: false,
      map: texture
    })

    const mesh2 = new THREE.Mesh(geometry2, material2)
    scene.add(mesh2)

  }

  /**
   * 创建一个闭合范围的模型数据
   * @param res {Object} 包含面的顶点数据face，UV面的顶点数据uvs
   */
  function generateVecData (arr) {
    const vec3List = [] // 顶点数组
    let faceList = [] // 三角面数组
    let faceVertexUvs = [] // 面的UV层队列，用于纹理和几何信息映射

    // t3---t2
    // |  \  |
    // t0---t1
    // UV面
    // 下三角[t0, t1, t3]
    // 上三角[t3, t1, t2]
    const t0 = [0, 0]
    const t1 = [1, 0]
    const t2 = [1, 1]
    const t3 = [0, 1]

    for (let i = 0; i < arr.length; i++) {
      const [x1, y1] = arr[i]
      vec3List.push([x1, y1, 0])
      vec3List.push([x1, y1, height])
    }

    // 1---3
    // | \ |
    // 0---2
    // 三角面顶点，没有顺序要求，但要跟UV面顺序一致
    // 下三角 [0,1,2]
    // 上三角 [1,2,3]
    for (let i = 0; i < vec3List.length - 2; i++) {
      if (i % 2 === 0) {
        // 下三角
        faceList = [...faceList, ...vec3List[i], ...vec3List[i + 2], ...vec3List[i + 1]]
        // UV
        faceVertexUvs = [...faceVertexUvs, ...t0, ...t1, ...t3]
      } else {
        // 上三角
        faceList = [...faceList, ...vec3List[i], ...vec3List[i + 1], ...vec3List[i + 2]]
        // UV
        faceVertexUvs = [...faceVertexUvs, ...t3, ...t1, ...t2]
      }
    }

    return {
      face: faceList,
      uvs: faceVertexUvs
    }
  }

  /**
   * 创建材质图
   * @param size 尺寸为2的n次方
   * @param color 颜色
   * @returns {*}
   */
  function generateTexture(size = 64, color ="#ff0000"){

    let canvas = document.createElement('canvas')
    canvas.width = size
    canvas.height = size
    let ctx = canvas.getContext('2d')
    let linearGradient = ctx.createLinearGradient(0,0,0,size)
    linearGradient.addColorStop(0.2, hexToRgba(color, 0.0))
    linearGradient.addColorStop(0.8, hexToRgba(color, 0.5))
    linearGradient.addColorStop(1.0, hexToRgba(color, 1.0))
    ctx.fillStyle = linearGradient
    ctx.fillRect(0,0, size, size)

    let texture = new THREE.Texture(canvas)
    texture.needsUpdate = true //必须
    return texture
  }

  /**
   * 将十六进制的颜色值转成rgba
   * @param {String} hex
   * @param {number} opacity
   * @returns {string}
   */
  function hexToRgba (hex, opacity = 1) {
    return 'rgba(' + parseInt('0x' + hex.slice(1, 3)) + ',' + parseInt('0x' + hex.slice(3, 5)) + ',' +
      parseInt('0x' + hex.slice(5, 7)) + ',' + opacity + ')'
  }

  // 动画
  function animate () {

    // 纹理偏移
    texture_offset -= 0.03 // 向上移动
    texture.offset.set(0, texture_offset)

    if (map) {
      map.render()
    }
    requestAnimationFrame(() => {
      animate()
    })
  }

  initLayer()

</script>

</body>

</html>

        
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