效果：

<template>
  <div>
    <el-container>
      <el-main>
        <div class="box-card-left">
          <div id="threejs" style="border: 1px solid red"></div>
          <div>
            <p>
              <el-button type="primary" @click="move()">沿着AB方向移动100</el-button>
              <el-button type="primary" @click="reset">重置</el-button>
            </p>
              <pre style="text-align: left;line-height: 20px;">
              已知直线AB上两个坐标，A点(-50,0,-50)、B点(100,0,100)。
              物体默认在A点，希望从A点开始沿着直线AB移动距离100,
              单位向量每个分量乘以100，得到的向量长度就是100，
              相当于得到一个沿着AB方向移动100的向量，
              这就是单位向量的意义，单位向量长度位1，
              乘以任何一个值S，就可以得到一个长度为S的向量。</pre>
          </div>
        </div>
      </el-main>
    </el-container>
  </div>
</template>
<script>
// 引入轨道控制器扩展库OrbitControls.js
import { OrbitControls } from "three/examples/jsm/controls/OrbitControls.js";
import { CSS3DObject, CSS3DSprite, CSS3DRenderer } from "three/examples/jsm/renderers/CSS3DRenderer.js";

export default {
  data() {
    return {
      sphereGeometry: null,
      group: null,
      camera: null,
      mesh: null,
      renderer: null,
      requestAnimationFrame_time: null,
      B: null,
      lengthVal: 0,
      normalizeVal: null,
      css3DRenderer: null,
      A: [-50,0,-50],
      B: [100,0,100]
    };
  },
  created() {},
  mounted() {
    this.name = this.$route.query.name;
    this.init();
  },
  methods: {
    goBack() {
      this.$router.go(-1);
    },
    init() {
      this.scene = new this.$three.Scene();
      const boxGeometry = new this.$three.BoxGeometry(30,40,50);
      const material = new this.$three.MeshBasicMaterial({color: 0x89aadd});
      this.mesh = new this.$three.Mesh(boxGeometry, material);
      this.scene.add(this.mesh);
      const axesHelper = new this.$three.AxesHelper(100);
      this.scene.add(axesHelper);

      this.createPoints(this.A, "A点");
      this.createPoints(this.B, "B点");
      this.createLine3();
      this.camera = new this.$three.PerspectiveCamera();
      this.camera.position.set(200,200,200);
      this.camera.lookAt(0,0,0);
      let v = new this.$three.Vector3();
      this.camera.getWorldDirection(v); // 获得相机视线方向的单位向量，并赋值给 v
      console.log(v);
      console.log(v.length());
      // 创建渲染器对象
      this.renderer = new this.$three.WebGLRenderer();
      this.renderer.setSize(1000,800);
      this.renderer.render(this.scene, this.camera);
      window.document.getElementById("threejs").appendChild(this.renderer.domElement);
      
      // 创建CSS3DRenderer 对象
      this.css3DRenderer = new CSS3DRenderer();
      this.css3DRenderer.setSize(1000,800);
      this.css3DRenderer.render(this.scene, this.camera);
      this.css3DRenderer.domElement.style.position = 'absolute';
      this.css3DRenderer.domElement.style.top = 0;
      this.css3DRenderer.domElement.style.pointerEvents = 'none';

      window.document.getElementById("threejs").appendChild(this.css3DRenderer.domElement);


      const controls = new OrbitControls(this.camera, this.renderer.domElement);
      controls.addEventListener("change", e => {
        this.renderer.render(this.scene, this.camera);
      })
      this.loopFun();
    },
    loopFun() {
      this.css3DRenderer.render(this.scene, this.camera);
      requestAnimationFrame(this.loopFun);
    },
    normalize_fn() {
      const A = new this.$three.Vector3(10,20,30);
      this.normalizeVal = A.normalize();
    },
    // 已知直线AB上两个坐标，A点(-50,0,-50)、B点(100,0,100)。物体默认在A点，希望从A点开始沿着直线AB移动距离100。
    createPoints(pointsArr, name) {
      // 创建缓存几何体对象
      const bufferGeometry = new this.$three.BufferGeometry();
      // 创建类型化数组来保存顶点数据
      // const vertices = new Float32Array([-50,0,-50]);
      const vertices = new Float32Array(pointsArr);
      // 通过创建  缓存属性对象  来表示顶点数据
      const attribute = new this.$three.BufferAttribute(vertices, 3);
      // 缓存几何体设置属性 position
      bufferGeometry.setAttribute("position", attribute);
      // 创建点材质对象
      const pointMaterial = new this.$three.PointsMaterial({
        color: 0xffaadd, // 点颜色
        size: 10, // 点大小
      });
      // 创建点对象
      const points = new this.$three.Points(bufferGeometry, pointMaterial);
      points.name = name;
      const dom = this.createDom(name);
      const sprite = new CSS3DSprite(dom);
      let x = pointsArr[0];
      let y = pointsArr[1] + 10;
      let z = pointsArr[2];
      sprite.position.set(x,y,z);
      // sprite.scale.set(0.5,0.5,0.5);
      points.add(sprite);
      this.scene.add(points);
    },
    createDom(text) {
      const dom = document.createElement("div");
      dom.style.border = '1px solid blue';
      dom.style.borderRadius = '5px';
      dom.style.fontSize = '14px';
      dom.style.padding = '1px 10px';
      dom.innerText = text;
      return dom;
    },
    move() {
      let A = new this.$three.Vector3(-50,0,-50);
      let B = new this.$three.Vector3(100,0,100);
      let AB = B.clone().sub(A);
      AB.normalize();
      const T = AB.clone().multiplyScalar(100);
      this.mesh.position.add(T);
      this.renderer.render(this.scene, this.camera);
    },
    reset() {
      this.mesh.position.set(0,0,0);
      this.renderer.render(this.scene, this.camera);
    },
    // 创建直线
    createLine3() {
      // 创建缓存几何体对象
      const bufferGeometry = new this.$three.BufferGeometry();
      let A = new this.$three.Vector3(-50,0,-50);
      let B = new this.$three.Vector3(100,0,100);
      let line3 = new this.$three.LineCurve3(A, B);
      let pointes = line3.getPoints(200);
      bufferGeometry.setFromPoints(pointes);
      const material = new this.$three.LineBasicMaterial({color: 0xffffff});
      const line = new this.$three.Line(bufferGeometry, material);
      this.scene.add(line);
    }
  },
};
</script>
<style lang="less" scoped>
.box-card-left {
  display: flex;
  align-items: flex-start;
  flex-direction: row;

  width: 100%;

  .box-right {
    img {
      width: 500px;
      user-select: none;
    }
  }
}
</style>