上一文中实现了用模型所在点的切线方式确定模型的朝向，这个章节是对上个章节的补充，用一种更简单的方式实现小车沿着轨道方向移动，如上文前半部分内容，需要创建场景，轨道，加载车的模型，一切就绪。

        threejs中有lookAt方法，这个方法不止是针对相机，也可以用于模型让模型对着某个点，因此让小车时刻对着轨迹的方向，只需要获取到小车所在为止的下一个点，并让小车始终把车头对着自己要去的那个点，就可以实现方向的控制。

  if (this.pathIndex === 999) {this.pathIndex = 0;}else{this.pathIndex += 1;}if (this.agv) {// 判断agv加载完成后，开始不断更新agv的位置let beginPoint = this.pathPoints[this.pathIndex]this.agv.position.set( beginPoint.x, beginPoint.y, beginPoint.z);//设置新的agv位置let endPoint = this.pathPoints[this.pathIndex+1];//获取小车下一个点的位置this.agv.lookAt(endPoint);//设置agv的模型朝向为切线的方向}

不过需要注意的是，在做循环执行的时候，不能判断小车是否走到最后一个点，因为小车走到最后一个点的时候，下一个点是不存在的，所以应该判断小车是否走到倒数第二个点，当小车走到倒数第二个点的时候就要让点的下标重置。否则会发生数组越界。因此上面要判断等于999就重置为0,

下面是全部的源码：

<template><div><div id="container"></div></div>
</template><script>
import * as THREE from 'three'
import {OrbitControls} from "three/addons/controls/OrbitControls";
import {GLTFLoader} from "three/addons/loaders/GLTFLoader";let scene;
export default {name: "agv-single",data() {return{camera:null,cameraCurve:null,renderer:null,container:null,controls:null,pathIndex:0,//小车的运动轨迹点索引agv:null,pathPoints:[],}},methods:{initScene(){scene = new THREE.Scene();},initCamera(){this.camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 10000);this.camera.position.set(500,500,500);},initLight(){//添加两个平行光const directionalLight1 = new THREE.DirectionalLight(0xffffff, 1.5);directionalLight1.position.set(-300,-300,600)scene.add(directionalLight1);const directionalLight2 = new THREE.DirectionalLight(0xffffff, 1.5);directionalLight2.position.set(600,200,600)scene.add(directionalLight2);},initRound(){//通过CatmullRomCurve3连接4个点绘制一条曲线，且闭合this.cameraCurve = new THREE.CatmullRomCurve3([new THREE.Vector3(-300, 40, 200),new THREE.Vector3(300, 40, 200),new THREE.Vector3(300, 40, -200),new THREE.Vector3(-300, 40, -200),],true);//参考路径上取1000个点，每个点上添加蓝色小球this.pathPoints = this.cameraCurve.getPoints(1000);//绘制一条路径参考线与上面的线重合，方便查看小车的行动轨迹const geometry = new THREE.BufferGeometry().setFromPoints(this.pathPoints);const material = new THREE.LineBasicMaterial({ color: '#000000', linewidth: 1, });//设置线条的颜色和宽度const curveObject = new THREE.Line(geometry, material);scene.add(curveObject);//在场景中加载一个agv小车，并将agv小车放在曲线的第一个点上const loader = new GLTFLoader()loader.load("/static/model/agv.gltf", (gltf) => {this.agv = gltf.scene;this.agv.position.set(this.pathPoints[0].x, this.pathPoints[0].y, this.pathPoints[0].z)   // 模型位置this.agv.scale.set(0.1,0.1,0.1)scene.add(this.agv)   // 加入场景})},initRenderer(){this.renderer = new THREE.WebGLRenderer({ antialias: true });this.container = document.getElementById("container")this.renderer.setSize(this.container.clientWidth, this.container.clientHeight);this.renderer.setClearColor('#AAAAAA', 1.0);this.container.appendChild(this.renderer.domElement);},initControl(){this.controls = new OrbitControls(this.camera, this.renderer.domElement);this.controls.enableDamping = true;this.controls.maxPolarAngle = Math.PI / 2.2;      // // 最大角度},initAnimate() {//参考路径的索引在1001~0中往复减少以实现小车循环行驶if (this.pathIndex === 999) {this.pathIndex = 0;}else{this.pathIndex += 1;}if (this.agv) {// 判断agv加载完成后，开始不断更新agv的位置let beginPoint = this.pathPoints[this.pathIndex]this.agv.position.set( beginPoint.x, beginPoint.y, beginPoint.z);//设置新的agv位置let endPoint = this.pathPoints[this.pathIndex+1];//获取小车下一个点的位置this.agv.lookAt(endPoint);//设置agv的模型朝向为切线的方向}requestAnimationFrame(this.initAnimate);this.renderer.render(scene, this.camera);},initPage(){this.initScene();this.initCamera();this.initLight();this.initRenderer();this.initControl();this.initRound();this.initAnimate();}},mounted() {this.initPage()}
}
</script><style scoped>
#container{position: absolute;width:100%;height:100%;overflow: hidden;
}</style>

效果图如下