java面试题全覆盖

目录

项目搭建

初始化three.js基础代码

加载环境模型

设置环境纹理

添加水面并设置阴影效果

实现幽灵小球的运动

实现相机切换和文字切屏

实现漫天星星和爱心样式

今天简单实现一个three.js的小Demo，加强自己对three知识的掌握与学习，只有在项目中才能灵活将所学知识运用起来，话不多说直接开始。

项目搭建

本案例还是借助框架书写three项目，借用vite构建工具搭建vue项目，vite这个构建工具如果有不了解的朋友，可以参考我之前对其讲解的文章：vite脚手架的搭建与使用 。搭建完成之后，用编辑器打开该项目，在终端执行 npm i 安装一下依赖，安装完成之后终端在安装 npm i three 即可。

因为我搭建的是vue3项目，为了便于代码的可读性，所以我将three.js代码单独抽离放在一个组件当中，在App根组件中进入引入该组件。具体如下：

<template>
  <!-- 圣诞3d贺卡 -->
  <christmasCard></christmasCard>
</template>

<script setup>
import christmasCard from './components/christmasCard.vue';
</script>

<style lang="less">
  *{
    margin: 0;
    padding: 0;
  }
</style>

初始化three.js基础代码

three.js开启必须用到的基础代码如下：

导入three库：

import * as THREE from 'three'

初始化场景：

const scene = new THREE.Scene()

初始化相机：

// 初始化相机
const camera = new THREE.PerspectiveCamera(75,window.innerWidth/window.innerHeight,0.1,1000)
camera.position.set(-3.23,2.98,4.06)
camera.updateProjectionMatrix()

初始化渲染器：

// 初始化渲染器
const renderer = new THREE.WebGLRenderer({
  antialias: true // 设置抗锯齿
})
renderer.setSize(window.innerWidth,window.innerHeight)
document.body.appendChild(renderer.domElement)

监听屏幕大小的改变，修改渲染器的宽高和相机的比例：

window.addEventListener("resize",()=>{ 
  renderer.setSize(window.innerWidth,window.innerHeight)
  camera.aspect = window.innerWidth/window.innerHeight
  camera.updateProjectionMatrix()
})

导入控制器：

import { OrbitControls } from "three/examples/jsm/controls/OrbitControls"
// 初始化控制器
const controls = new OrbitControls(camera,renderer.domElement)
controls.enableDamping = true // 设置控制阻尼

设置渲染函数：

const render = () =>{ 
  requestAnimationFrame(render)
  renderer.render(scene,camera)
  controls.update()
}

进行挂载：

import { onMounted } from "vue";
onMounted(()=>{
  render()
})

ok，写完基础代码之后，接下来开始具体的Demo实操。 

加载环境模型

经过前几篇对three.js小demo的训练，相信大家对加载模型可谓是得心应手了吧，无非就四步嘛：

第一步引入加载GLTF模型和压缩模型的第三方库：

// 加载GLTF模型
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader';
// 解压GLTF模型
import { DRACOLoader } from 'three/examples/jsm/loaders/DRACOLoader';

第二步初始化loader：

const dracoLoader = new DRACOLoader()
dracoLoader.setDecoderPath("/draco/")
const gltfLoader = new GLTFLoader()
gltfLoader.setDRACOLoader(dracoLoader)

第三步就是加载gltf模型：

gltfLoader.load("./model/scene.glb",(gltf)=>{
  const model = gltf.scene
  model.scale.set(0.3,0.3,0.3)
  scene.add(model)
})

第四步就是根据具体情况添加光源：

// 添加平行光
const light = new THREE.DirectionalLight(0xffffff,1)
light.position.set(0,50,0)
scene.add(light)

设置环境纹理

这里的话通过RGBELoader将HDR(高动态范围)格式的图片数据加载到Three.js中，并将其转换为Cubemap格式的文本形式，以用于创建更高质量、更真实的3D场景和物体。

// 解析 HDR 纹理数据
import { RGBELoader } from 'three/examples/jsm/loaders/RGBELoader'

let rgbeLoader = new RGBELoader()
rgbeLoader.load('./textures/sky.hdr',(texture)=>{
  texture.mapping = THREE.EquirectangularReflectionMapping
  scene.background = texture
  scene.environment = texture
})

当然我们也可以设置一下环境纹理的色调映射，如下：

// 设置色调映射
renderer.toneMapping = THREE.ACESFilmicToneMapping // 色调映射技术，是在电影和电视行业中广泛使用的一种技术
renderer.toneMappingExposure = 0.3 // 色调亮光程度

这样可让环境稍微暗一点，更具有朦胧感：

添加水面并设置阴影效果

接下来通过three给我们提供的库进行创建一个水面，如下：

// 导入水面
import { Water } from 'three/examples/jsm/objects/Water2'
// 创建水面
const waterGeometry = new THREE.CircleGeometry(100,100)
const water = new Water(waterGeometry,{
  textureWidth: 1024,
  textureHeight: 1024,
  color: 0xeeeeff,
  flowDirection: new THREE.Vector2(1,1),
  scale: 100
})
water.rotation.x = -Math.PI /2
water.position.y = -0.1
scene.add(water)

接下来通过设置一个点光源，然后给模型添加接受阴影效果，如下：

// 添加点光源
const pointLight = new THREE.PointLight(0xffffff,2,10)
pointLight.position.set(-0.05,0.8,0.1)
pointLight.castShadow = true
scene.add(pointLight)

实现幽灵小球的运动

接下来我们通过创建一个点光源组来实现三个发光的幽灵小球：

// 创建点光源组
const pointLightGroup = new THREE.Group();
pointLightGroup.position.set(-8, 2.5, -1.5);
let radius = 3;
let pointLightArr = [];
for (let i = 0; i < 3; i++) {
  // 创建球体当灯泡
  const sphereGeometry = new THREE.SphereGeometry(0.2, 32, 32);
  const sphereMaterial = new THREE.MeshStandardMaterial({
    color: 0xffffff,
    emissive: 0xffffff,
    emissiveIntensity: 10,
  });
  const sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);
  pointLightArr.push(sphere);
  sphere.position.set(
    radius * Math.cos((i * 2 * Math.PI) / 3),
    Math.cos((i * 2 * Math.PI) / 3),
    radius * Math.sin((i * 2 * Math.PI) / 3)
  );

  let pointLight = new THREE.PointLight(0xffffff, 50);
  sphere.add(pointLight);

  pointLightGroup.add(sphere);
}
scene.add(pointLightGroup);

因为要想实现动画效果，这里需要安装一个动画库，看参考我之前的文章： Gsap动画库基本使用与原理 ，这里就不再赘述。

通过使用补间函数，从0到2π，使灯泡旋转：

let options = {
  angle: 0,
};
gsap.to(options, {
  angle: Math.PI * 2,
  duration: 10,
  repeat: -1,
  ease: "linear",
  onUpdate: () => {
    pointLightGroup.rotation.y = options.angle;
    pointLightArr.forEach((item, index) => {
      item.position.set(
        radius * Math.cos((index * 2 * Math.PI) / 3),
        Math.cos((index * 2 * Math.PI) / 3 + options.angle * 5),
        radius * Math.sin((index * 2 * Math.PI) / 3)
      );
    });
  },
});

最后实现的效果如下：

实现相机切换和文字切屏

首先先定义一个移动函数，如下：

// 使用补间动画移动相机
let timeLine1 = gsap.timeline()
let timeLine2 = gsap.timeline()
// 定义相机移动函数
const translateCamera = (position,target) =>{ 
  timeLine1.to(camera.position, {
    x: position.x,
    y: position.y,
    z: position.z,
    duration: 1,
    ease: "power2.inOut",
  });

  timeLine2.to(controls.target, {
    x: target.x,
    y: target.y,
    z: target.z,
    duration: 1,
    ease: "power2.inOut",
  });
}

接下来定义文字切屏的场景：

// 添加文字场景
let scenes = [
  {
    text:'圣诞快乐',
    callback:()=>{
      // 执行函数切换位置
      translateCamera(
        new THREE.Vector3(-3.23, 3, 4.06),
        new THREE.Vector3(-8, 2, 0)
      );
    }
  },
  {
    text:'感谢世界这么大还能遇见你',
    callback:()=>{
      translateCamera(new THREE.Vector3(7, 0, 23), new THREE.Vector3(0, 0, 0))
    }
  },
  {
    text:'愿与你探寻整个世界',
    callback:()=>{
      translateCamera(new THREE.Vector3(10, 3, 0), new THREE.Vector3(5, 2, 0))
    }
  },
  {
    text:'愿将天上的星星送给你',
    callback:()=>{
      translateCamera(new THREE.Vector3(7, 0, 23), new THREE.Vector3(0, 0, 0))
    }
  },
  {
    text:'愿永远和你在一起',
    callback:()=>{
      translateCamera(
        new THREE.Vector3(-20, 1.3, 6.6),
        new THREE.Vector3(5, 2, 0)
      );
    }
  },
]

 接下来通过监听鼠标滚轮事件：

let index = ref(0)
let isAnimate = false;
// 监听鼠标滚轮事件
window.addEventListener(
  "wheel",
  (e) => {
    if (isAnimate) return;
    isAnimate = true;
    if (e.deltaY > 0) {
      index.value++;
      if (index.value > scenes.length - 1) {
        index.value = 0;
      }
    }
    scenes[index.value].callback();
    setTimeout(() => {
      isAnimate = false;
    }, 1000);
  },
  false
);

接下来设置文字展示的样式：

<template>
  <div 
    class="scenes"
    style="
      position: fixed;
      left: 0;
      top: 0;
      z-index: 10;
      pointer-events: none;
      transition: all 1s;
    "
    :style="{
      transform: `translate3d(0, ${-index * 100}vh, 0)`,
    }"
  >
    <div v-for="item in scenes" style="width: 100vw;height: 100vh;">
      <h1 style="padding: 100px 50px; font-size: 50px; color: #fff">{{ item.text }}</h1>
    </div>
  </div>
</template>

实现漫天星星和爱心样式

接下来通过InstancedMesh网格渲染优化方式，允许在渲染多个相同的模型时，只需要创建一个几何体和材质，然后通过实例化渲染多个对象，从而大大提高渲染性能。

// 实例化创建漫天星星
let starsInstance = new THREE.InstancedMesh(
  new THREE.SphereGeometry(0.1, 32, 32),
  new THREE.MeshStandardMaterial({
    color: 0xffffff,
    emissive: 0xffffff, //模拟自发光材质，并且不会受到光照的影响。
    emissiveIntensity: 10, // 控制发光效果强度
  }),
  100 // 创建100个
);

接下来将信息渲染到环境当中：

// 星星随机到天上
let starsArr = [];
let endArr = [];
for (let i = 0; i < 100; i++) {
  let x = Math.random() * 100 - 50;
  let y = Math.random() * 100 - 50;
  let z = Math.random() * 100 - 50;
  starsArr.push(new THREE.Vector3(x, y, z));

  let matrix = new THREE.Matrix4();
  matrix.setPosition(x, y, z);
  starsInstance.setMatrixAt(i, matrix);
}
scene.add(starsInstance);

接下来实现爱心的效果：

// 创建爱心路径
let heartShape = new THREE.Shape();
heartShape.moveTo(25, 25);
heartShape.bezierCurveTo(25, 25, 20, 0, 0, 0);
heartShape.bezierCurveTo(-30, 0, -30, 35, -30, 35);
heartShape.bezierCurveTo(-30, 55, -10, 77, 25, 95);
heartShape.bezierCurveTo(60, 77, 80, 55, 80, 35);
heartShape.bezierCurveTo(80, 35, 80, 0, 50, 0);
heartShape.bezierCurveTo(35, 0, 25, 25, 25, 25);

// 根据爱心路径获取点
let center = new THREE.Vector3(0, 2, 10);
for (let i = 0; i < 100; i++) {
  let point = heartShape.getPoint(i / 100);
  endArr.push(
    new THREE.Vector3(
      point.x * 0.1 + center.x,
      point.y * 0.1 + center.y,
      center.z
    )
  );
}

接下啦创建爱心动画：

// 创建爱心动画
function makeHeart() {
  let params = {
    time: 0,
  };

  gsap.to(params, {
    time: 1,
    duration: 1,
    onUpdate: () => {
      for (let i = 0; i < 100; i++) {
        let x = starsArr[i].x + (endArr[i].x - starsArr[i].x) * params.time;
        let y = starsArr[i].y + (endArr[i].y - starsArr[i].y) * params.time;
        let z = starsArr[i].z + (endArr[i].z - starsArr[i].z) * params.time;
        let matrix = new THREE.Matrix4();
        matrix.setPosition(x, y, z);
        starsInstance.setMatrixAt(i, matrix);
      }
      starsInstance.instanceMatrix.needsUpdate = true;
    },
  });
}

function restoreHeart() {
  let params = {
    time: 0,
  };

  gsap.to(params, {
    time: 1,
    duration: 1,
    onUpdate: () => {
      for (let i = 0; i < 100; i++) {
        let x = endArr[i].x + (starsArr[i].x - endArr[i].x) * params.time;
        let y = endArr[i].y + (starsArr[i].y - endArr[i].y) * params.time;
        let z = endArr[i].z + (starsArr[i].z - endArr[i].z) * params.time;
        let matrix = new THREE.Matrix4();
        matrix.setPosition(x, y, z);
        starsInstance.setMatrixAt(i, matrix);
      }
      starsInstance.instanceMatrix.needsUpdate = true;
    },
  });
}

在场景中进行调用函数即可：

在定义一个定时器，让页面在刚加载的时候就开始调用，在设置一个监听函数，当用户点击屏幕的时候，定时器清除，然后用户可以自行手动去切换场景：

var timer = setInterval(function() {
  var scrollEvent = new WheelEvent('wheel', { deltaY: 100 });
  window.dispatchEvent(scrollEvent);
}, 3000);

document.addEventListener('click', function() {
  clearInterval(timer);
});

相关效果图如下：

demo做完，给出本案例的完整代码：（获取素材也可以私信博主）

<template>
  <div 
    class="scenes"
    style="
      position: fixed;
      left: 0;
      top: 0;
      z-index: 10;
      pointer-events: none;
      transition: all 1s;
    "
    :style="{
      transform: `translate3d(0, ${-index * 100}vh, 0)`,
    }"
  >
    <div v-for="item in scenes" style="width: 100vw;height: 100vh;">
      <h1 style="padding: 100px 50px; font-size: 50px; color: #fff">{{ item.text }}</h1>
    </div>
  </div>
</template>

<script setup>
import { ref } from 'vue';
import * as THREE from 'three'
// 导入动画库
import gsap from 'gsap';
import { onMounted } from "vue";
// 加载GLTF模型
import { GLTFLoader } from 'three/examples/jsm/loaders/GLTFLoader';
// 解压GLTF模型
import { DRACOLoader } from 'three/examples/jsm/loaders/DRACOLoader';
// 导入控制器
import { OrbitControls } from 'three/examples/jsm/controls/OrbitControls';
// 解析 HDR 纹理数据
import { RGBELoader } from 'three/examples/jsm/loaders/RGBELoader'
// 导入水面
import { Water } from 'three/examples/jsm/objects/Water2'

// 初始化场景
const scene = new THREE.Scene()
// 初始化相机
const camera = new THREE.PerspectiveCamera(75,window.innerWidth/window.innerHeight,0.1,1000)
camera.position.set(-3.23,2.98,4.06)
camera.updateProjectionMatrix()

// 初始化渲染器
const renderer = new THREE.WebGLRenderer({
  antialias: true // 设置抗锯齿
})
renderer.setSize(window.innerWidth,window.innerHeight)
document.body.appendChild(renderer.domElement)

// 监听页面变化
window.addEventListener("resize",()=>{  
  renderer.setSize(window.innerWidth,window.innerHeight)
  camera.aspect = window.innerWidth/window.innerHeight
  camera.updateProjectionMatrix()
})

// 设置色调映射
renderer.toneMapping = THREE.ACESFilmicToneMapping // 色调映射技术，是在电影和电视行业中广泛使用的一种技术
renderer.toneMappingExposure = 0.3 // 色调亮光程度
// 设置渲染器允许阴影效果
renderer.shadowMap.enabled = true
renderer.physicallyCorrectLights = true

// 初始化控制器
const controls = new OrbitControls(camera,renderer.domElement)
controls.target.set(-8,2,0)
controls.enableDamping = true // 设置控制阻尼

const render = () =>{ 
  requestAnimationFrame(render)
  renderer.render(scene,camera)
  controls.update()
}

onMounted(()=>{
  render()
})

// 初始化loader
const dracoLoader = new DRACOLoader()
dracoLoader.setDecoderPath("/draco/")
const gltfLoader = new GLTFLoader()
gltfLoader.setDRACOLoader(dracoLoader)
// 加载模型
gltfLoader.load("./model/scene.glb",(gltf)=>{
  const model = gltf.scene
  model.traverse((child)=>{
    if(child.name === 'Plane'){
      child.visible = false
    }
    // 设置物体是允许接收和投射阴影的
    if(child.isMesh){
      child.castShadow = true
      child.receiveShadow = true
    }
  })
  scene.add(model)
})

// 创建水面
const waterGeometry = new THREE.CircleGeometry(100,100)
const water = new Water(waterGeometry,{
  textureWidth: 1024,
  textureHeight: 1024,
  color: 0xeeeeff,
  flowDirection: new THREE.Vector2(1,1),
  scale: 100
})
water.rotation.x = -Math.PI /2
water.position.y = -0.1
scene.add(water)

// 添加平行光
const light = new THREE.DirectionalLight(0xffffff,1)
light.position.set(0,50,0)
scene.add(light)
// 添加点光源
const pointLight = new THREE.PointLight(0xffffff,50,10)
pointLight.position.set(0.1, 2.4, 0)
pointLight.castShadow = true
scene.add(pointLight)

// 创建点光源组
const pointLightGroup = new THREE.Group();
pointLightGroup.position.set(-8, 2.5, -1.5);
let radius = 3;
let pointLightArr = [];
for (let i = 0; i < 3; i++) {
  // 创建球体当灯泡
  const sphereGeometry = new THREE.SphereGeometry(0.2, 32, 32);
  const sphereMaterial = new THREE.MeshStandardMaterial({
    color: 0xffffff,
    emissive: 0xffffff,
    emissiveIntensity: 10,
  });
  const sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);
  pointLightArr.push(sphere);
  sphere.position.set(
    radius * Math.cos((i * 2 * Math.PI) / 3),
    Math.cos((i * 2 * Math.PI) / 3),
    radius * Math.sin((i * 2 * Math.PI) / 3)
  );

  let pointLight = new THREE.PointLight(0xffffff, 50);
  sphere.add(pointLight);

  pointLightGroup.add(sphere);
}
scene.add(pointLightGroup);

// 使用补间函数，从0到2π，使灯泡旋转
let options = {
  angle: 0,
};
gsap.to(options, {
  angle: Math.PI * 2,
  duration: 10,
  repeat: -1,
  ease: "linear",
  onUpdate: () => {
    pointLightGroup.rotation.y = options.angle;
    pointLightArr.forEach((item, index) => {
      item.position.set(
        radius * Math.cos((index * 2 * Math.PI) / 3),
        Math.cos((index * 2 * Math.PI) / 3 + options.angle * 5),
        radius * Math.sin((index * 2 * Math.PI) / 3)
      );
    });
  },
});

// 加载纹理贴图
let rgbeLoader = new RGBELoader()
rgbeLoader.load('./textures/sky.hdr',(texture)=>{
  texture.mapping = THREE.EquirectangularReflectionMapping
  scene.background = texture
  scene.environment = texture
})

// 使用补间动画移动相机
let timeLine1 = gsap.timeline()
let timeLine2 = gsap.timeline()
// 定义相机移动函数
const translateCamera = (position,target) =>{ 
  timeLine1.to(camera.position, {
    x: position.x,
    y: position.y,
    z: position.z,
    duration: 1,
    ease: "power2.inOut",
  });

  timeLine2.to(controls.target, {
    x: target.x,
    y: target.y,
    z: target.z,
    duration: 1,
    ease: "power2.inOut",
  });
}

// 添加文字场景
let scenes = [
  {
    text:'圣诞快乐',
    callback:()=>{
      // 执行函数切换位置
      translateCamera(
        new THREE.Vector3(-3.23, 3, 4.06),
        new THREE.Vector3(-8, 2, 0)
      );
      restoreHeart()
    }
  },
  {
    text:'感谢世界这么大还能遇见你',
    callback:()=>{
      translateCamera(new THREE.Vector3(7, 0, 23), new THREE.Vector3(0, 0, 0))
    }
  },
  {
    text:'愿与你探寻整个世界',
    callback:()=>{
      translateCamera(new THREE.Vector3(10, 3, 0), new THREE.Vector3(5, 2, 0))
    }
  },
  {
    text:'愿将天上的星星送给你',
    callback:()=>{
      translateCamera(new THREE.Vector3(7, 0, 23), new THREE.Vector3(0, 0, 0))
      makeHeart()
    }
  },
  {
    text:'愿永远和你在一起',
    callback:()=>{
      translateCamera(
        new THREE.Vector3(-20, 1.3, 6.6),
        new THREE.Vector3(5, 2, 0)
      );
    }
  },
]

let index = ref(0)
let isAnimate = false;
// 监听鼠标滚轮事件
window.addEventListener(
  "wheel",
  (e) => {
    if (isAnimate) return;
    isAnimate = true;
    if (e.deltaY > 0) {
      index.value++;
      if (index.value > scenes.length - 1) {
        index.value = 0;
      }
    }
    scenes[index.value].callback();
    setTimeout(() => {
      isAnimate = false;
    }, 1000);
  },
  false
);

// 实例化创建漫天星星
let starsInstance = new THREE.InstancedMesh(
  new THREE.SphereGeometry(0.1, 32, 32),
  new THREE.MeshStandardMaterial({
    color: 0xffffff,
    emissive: 0xffffff, //模拟自发光材质，并且不会受到光照的影响。
    emissiveIntensity: 10, // 控制发光效果强度
  }),
  100 // 创建100个
);
// 星星随机到天上
let starsArr = [];
let endArr = [];
for (let i = 0; i < 100; i++) {
  let x = Math.random() * 100 - 50;
  let y = Math.random() * 100 - 50;
  let z = Math.random() * 100 - 50;
  starsArr.push(new THREE.Vector3(x, y, z));

  let matrix = new THREE.Matrix4();
  matrix.setPosition(x, y, z);
  starsInstance.setMatrixAt(i, matrix);
}
scene.add(starsInstance);

// 创建爱心路径
let heartShape = new THREE.Shape();
heartShape.moveTo(25, 25);
heartShape.bezierCurveTo(25, 25, 20, 0, 0, 0);
heartShape.bezierCurveTo(-30, 0, -30, 35, -30, 35);
heartShape.bezierCurveTo(-30, 55, -10, 77, 25, 95);
heartShape.bezierCurveTo(60, 77, 80, 55, 80, 35);
heartShape.bezierCurveTo(80, 35, 80, 0, 50, 0);
heartShape.bezierCurveTo(35, 0, 25, 25, 25, 25);

// 根据爱心路径获取点
let center = new THREE.Vector3(0, 2, 10);
for (let i = 0; i < 100; i++) {
  let point = heartShape.getPoint(i / 100);
  endArr.push(
    new THREE.Vector3(
      point.x * 0.1 + center.x,
      point.y * 0.1 + center.y,
      center.z
    )
  );
}

// 创建爱心动画
function makeHeart() {
  let params = {
    time: 0,
  };

  gsap.to(params, {
    time: 1,
    duration: 1,
    onUpdate: () => {
      for (let i = 0; i < 100; i++) {
        let x = starsArr[i].x + (endArr[i].x - starsArr[i].x) * params.time;
        let y = starsArr[i].y + (endArr[i].y - starsArr[i].y) * params.time;
        let z = starsArr[i].z + (endArr[i].z - starsArr[i].z) * params.time;
        let matrix = new THREE.Matrix4();
        matrix.setPosition(x, y, z);
        starsInstance.setMatrixAt(i, matrix);
      }
      starsInstance.instanceMatrix.needsUpdate = true;
    },
  });
}

function restoreHeart() {
  let params = {
    time: 0,
  };

  gsap.to(params, {
    time: 1,
    duration: 1,
    onUpdate: () => {
      for (let i = 0; i < 100; i++) {
        let x = endArr[i].x + (starsArr[i].x - endArr[i].x) * params.time;
        let y = endArr[i].y + (starsArr[i].y - endArr[i].y) * params.time;
        let z = endArr[i].z + (starsArr[i].z - endArr[i].z) * params.time;
        let matrix = new THREE.Matrix4();
        matrix.setPosition(x, y, z);
        starsInstance.setMatrixAt(i, matrix);
      }
      starsInstance.instanceMatrix.needsUpdate = true;
    },
  });
}

var timer = setInterval(function() {
  var scrollEvent = new WheelEvent('wheel', { deltaY: 100 });
  window.dispatchEvent(scrollEvent);
}, 3000);

document.addEventListener('click', function() {
  clearInterval(timer);
});

</script>
<style lang="less" scoped></style>