ThreeJS-3D教学三：平移缩放+物体沿轨迹运动

我们在项目中会有一些这样的需求，我们可视化一个场景，需要俯视、平移、缩放，方便观察场景中的数据或者模型，之所以把这个案例拿出来
1、这是个很实用的需求，我相信很多人会用到
2、我自己认为在实际案例中我们可以学习相关知识点更易吸收些
为了丰富本篇文章知识点，我还加入了一个物体沿轨迹运动的场景，下面代码会介绍到，回到之前的问题three中可以利用对 OrbitControls 的设置很轻松的实现相关场景，代码如下：

controls = new OrbitControls( camera, renderer.domElement );
  // 移动端控制平移 缩放
  // controls.touches = {
  //   ONE: THREE.TOUCH.PAN,
  //   TWO: THREE.TOUCH.DOLLY_PAN
  // };
  // PC 左平移，右旋转 滚轮放大缩小   默认是右平移
  controls.mouseButtons = {
    LEFT: THREE.MOUSE.PAN,
    MIDDLE: THREE.MOUSE.DOLLY,
    RIGHT: THREE.MOUSE.ROTATE
  };
  // 设置最大最小视距
  controls.minDistance = 20;
  controls.maxDistance = 1000;
  controls.autoRotate = false;
  controls.enableRotate = false;
  controls.enablePan = true;

需要注意的是移动端和PC是不同的配置，minDistance和maxDistance按实际需求设置即可，到这一步只是对controls的操作，已经有能力实现效果了，但是camera的设置也是不可或缺的，即camera必须是俯视的

先上下整体效果图
在这里插入图片描述
看下代码：

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    body {
      width: 100%;
      height: 100%;
    }
    * {
      margin: 0;
      padding: 0;
    }
    .label {
      font-size: 20px;
      color: #000;
      font-weight: 700;
    }
  </style>
</head>
<body>
<div id="container"></div>
<script type="importmap">
  {
    "imports": {
      "three": "../three-155/build/three.module.js",
      "three/addons/": "../three-155/examples/jsm/"
    }
  }
</script>
<script type="module">
import * as THREE from 'three';
import Stats from 'three/addons/libs/stats.module.js';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
import { CSS2DRenderer, CSS2DObject } from 'three/addons/renderers/CSS2DRenderer.js';
let stats, labelRenderer, curve, movingObjects;
let camera, scene, renderer, mesBox, target, controls;
const group = new THREE.Group();
let progress = 0; // 物体运动时在运动路径的初始位置，范围0~1
const velocity = 0.0005; // 影响运动速率的一个值，范围0~1，需要和渲染频率结合计算才能得到真正的速率
let widthImg = 200;
let heightImg = 200;
init();
initHelp();
initLight();
axesHelperWord();
animate();
// 添加一个物体
mesBox = addGeometries();
// 添加平面
addPlane();
// 添加路径
makeCurve();
// 添加一个运动的物体
movingObjects = addMovingObjects();


window.addEventListener('mousemove', mousemoveFun);

function addPlane() {
  // 创建一个平面 PlaneGeometry(width, height, widthSegments, heightSegments)
  const planeGeometry = new THREE.PlaneGeometry(widthImg, heightImg, 1, 1);
  // 创建 Lambert 材质：会对场景中的光源作出反应，但表现为暗淡，而不光亮。
  const planeMaterial = new THREE.MeshLambertMaterial({
    color: 0xffffff
  });
  const plane = new THREE.Mesh(planeGeometry, planeMaterial);
  // 以自身中心为旋转轴，绕 x 轴顺时针旋转 45 度
  plane.rotation.x = -0.5 * Math.PI;
  plane.position.set(0, -4, 0);
  scene.add(plane);
}

function addGeometries() {
  let img = new THREE.TextureLoader().load('../materials/img/view4.jpg');
  img.repeat.x = img.repeat.y = 5;
  const geometry = new THREE.BoxGeometry( 10, 10, 10 );
  let material = new THREE.MeshPhongMaterial({
    map: img,
    flatShading: true,
    side: THREE.DoubleSide,
    transparent: 1
  });

  const mesh = new THREE.Mesh( geometry, material );
  mesh.position.x = 0;
  mesh.position.y = 0;
  mesh.position.z = -20;
  scene.add( mesh );
  return mesh;
}

function addMovingObjects() {
  let img = new THREE.TextureLoader().load('../materials/img/view3.jpg');
  const geometry = new THREE.BoxGeometry( 10, 10, 10 );
  const material = new THREE.MeshPhongMaterial({
    map: img,
    flatShading: true,
    side: THREE.DoubleSide,
    transparent: 1
  });
  const mesh = new THREE.Mesh( geometry, material );
  scene.add( mesh );
  return mesh;
}

function makeCurve() {
  // 创建一个环形路径
  curve = new THREE.CatmullRomCurve3([
    new THREE.Vector3(80, 0, 80),
    new THREE.Vector3(80, 0, -80),
    new THREE.Vector3(-80, 0, -80),
    new THREE.Vector3(-80, 0, 80)
  ]);
  curve.curveType = "catmullrom";
  curve.closed = true;//设置是否闭环
  curve.tension = 0; //设置线的张力，0为无弧度折线

  // 为曲线添加材质在场景中显示出来，不显示也不会影响运动轨迹，相当于一个Helper
  const points = curve.getPoints(20);
  const geometry = new THREE.BufferGeometry().setFromPoints(points);
  const material = new THREE.LineBasicMaterial({
    color: '#f00',
    linewidth: 1
  });

  // Create the final object to add to the scene
  const curveObject = new THREE.Line(geometry, material);
  curveObject.position.y = 1;
  curveObject.visible = false;
  scene.add(curveObject);
}

function mousemoveFun() {
  let width = widthImg;
  let height = heightImg;
  let newPo;
  let newPoHeight;

  const prevPos = camera.position.clone();

  if (camera.position['x'] > width / 2) {
    newPo = width / 2 - 0.01;
    camera.position.set(newPo, prevPos.y, prevPos.z);
    controls.target = new THREE.Vector3(newPo, 0, prevPos.z);
    controls.enablePan = false;
  } else if (camera.position['x'] < -width / 2) {
    newPo = -width / 2 + 0.01;
    camera.position.set(newPo, prevPos.y, prevPos.z);
    controls.target = new THREE.Vector3(newPo, 0, prevPos.z);
    controls.enablePan = false;
  } else if (camera.position['z'] > height / 2) {
    // 因为我们的坐标系 y轴在上 所以平移时 height 即是 z
    newPoHeight = height / 2 - 0.01;
    camera.position.set(prevPos.x, prevPos.y, newPoHeight);
    controls.target = new THREE.Vector3(prevPos.x, 0, newPoHeight);
    controls.enablePan = false;
  } else if (camera.position['z'] < -height / 2) {
    newPoHeight = -height / 2 + 0.01;
    camera.position.set(prevPos.x, prevPos.y, newPoHeight);
    controls.target = new THREE.Vector3(prevPos.x, 0, newPoHeight);
    controls.enablePan = false;
  } else {
    controls.enablePan = true;
  }
}

function init() {

  camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 10, 2000 );
  camera.up.set(0, 1, 0);
  camera.position.set(0, 100, 0);
  camera.lookAt(0, 0, 0);

  scene = new THREE.Scene();
  // scene.background = new THREE.Color( '#ccc' );

  renderer = new THREE.WebGLRenderer( { antialias: true } );
  renderer.setPixelRatio( window.devicePixelRatio );
  renderer.setSize( window.innerWidth, window.innerHeight );
  document.body.appendChild( renderer.domElement );

  labelRenderer = new CSS2DRenderer();
  labelRenderer.setSize( window.innerWidth, window.innerHeight );
  labelRenderer.domElement.style.position = 'absolute';
  labelRenderer.domElement.style.top = '0px';
  labelRenderer.domElement.style.pointerEvents = 'none';
  document.getElementById( 'container' ).appendChild( labelRenderer.domElement );

  controls = new OrbitControls( camera, renderer.domElement );
  // 移动端控制平移 缩放
  // controls.touches = {
  //   ONE: THREE.TOUCH.PAN,
  //   TWO: THREE.TOUCH.DOLLY_PAN
  // };
  // PC 左平移，右旋转 滚轮放大缩小   默认是右平移
  controls.mouseButtons = {
    LEFT: THREE.MOUSE.PAN,
    MIDDLE: THREE.MOUSE.DOLLY,
    RIGHT: THREE.MOUSE.ROTATE
  };
  // 设置最大最小视距
  controls.minDistance = 20;
  controls.maxDistance = 1000;
  controls.autoRotate = false;
  controls.enableRotate = false;
  controls.enablePan = true;

  window.addEventListener( 'resize', onWindowResize );

  stats = new Stats();
  stats.setMode(1); // 0: fps, 1: ms
  document.body.appendChild( stats.dom );

  scene.add( group );
}

function initLight() {
  let spotLight;
  spotLight = new THREE.SpotLight( 0xffffff, 500 );
  spotLight.name = 'Spot Light';
  spotLight.angle = Math.PI / 5;
  spotLight.penumbra = 0.1;
  spotLight.position.set( 0, 5, 10 );
  spotLight.castShadow = true;
  spotLight.shadow.camera.near = 2;
  spotLight.shadow.camera.far = 100;
  spotLight.shadow.mapSize.width = 1024;
  spotLight.shadow.mapSize.height = 1024;
  scene.add( spotLight );

  const AmbientLight = new THREE.AmbientLight(0xCCCCCC, 2);
  scene.add( AmbientLight );
}

function initHelp() {
  // const size = 100;
  // const divisions = 5;
  // const gridHelper = new THREE.GridHelper( size, divisions );
  // scene.add( gridHelper );

  // The X axis is red. The Y axis is green. The Z axis is blue.
  const axesHelper = new THREE.AxesHelper( 100 );
  scene.add( axesHelper );
}

function axesHelperWord() {
  let xP = addWord('X轴');
  let yP = addWord('Y轴');
  let zP = addWord('Z轴');
  xP.position.set(50, 0, 0);
  yP.position.set(0, 50, 0);
  zP.position.set(0, 0, 50);
}

function addWord(word) {
  let name = `<span>${word}</span>`;
  let moonDiv = document.createElement( 'div' );
  moonDiv.className = 'label';
  // moonDiv.textContent = 'Moon';
  // moonDiv.style.marginTop = '-1em';
  moonDiv.innerHTML = name;
  const label = new CSS2DObject( moonDiv );
  group.add( label );
  return label;
}

function onWindowResize() {
  camera.aspect = window.innerWidth / window.innerHeight;
  camera.updateProjectionMatrix();
  renderer.setSize( window.innerWidth, window.innerHeight );
}

function animate() {
  requestAnimationFrame( animate );

  // mesh绕自身中心的 y 轴自转
  if (mesBox) {
    mesBox.rotation.y += 0.01;
  }

  if (curve && movingObjects) {
    if (progress <= 1 - velocity) {
      // 获取样条曲线指定点坐标
      const point = curve.getPointAt(progress);
      movingObjects.position.set(point.x, point.y, point.z);
      progress += velocity;
    } else {
      progress = 0;
    }
  }

  stats.update();
  controls.update();
  labelRenderer.render( scene, camera );
  renderer.render( scene, camera );
}
</script>
</body>
</html>

这里是全部代码，可以看出 three用的是 155版本，大家从官网上下载到本地改下路径即可。图片url你可以换成本地图片，项目就能跑起来了。

中间立方体在做了一个环绕自身y轴旋转，外面的立方体通过获取curve上的坐标点，沿着curve的轨迹运动。

这里有一些新的知识点：

new THREE.TextureLoader().load(‘…/materials/img/view3.jpg’);
TextureLoader是three加载图片的方法，我们还可以这样用
let loader = new THREE.TextureLoader();
loader.load(‘url’, (img) => {
// img 这个img就是加载完成后的图片
});

这时就一个疑问了，同步还是异步，我们来看源码
在这里插入图片描述
其实还是异步，拿到图片后我们发现material有一个map参数，可以接收图片作为材质，这样material就可以做的很丰富了，side是指物体的正反两面，THREE.DoubleSide即两面都要渲染，如果我们只看外面，不要设置这里，这样也能节省一些性能

 let material = new THREE.MeshPhongMaterial({
    map: img,
    flatShading: true,
    side: THREE.DoubleSide,
    transparent: 1
  });

最后一个知识点，即物体沿着轨迹运动，我们把这一行代码
curveObject.visible = false; 改为 true 大家就可以看到这个轨迹了。
逻辑代码中已经写的很详细了，大家也可以思考下还有哪些方法可以作为curve使用。
如果感觉有用，点个赞不过分吧！！！

ThreeJS-3D教学三：平移缩放+物体沿轨迹运动

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