使用vue学习three.js之粒子和粒子系统-通过THREE.PointsMaterial材质使用HTML5画布格式化粒子

1.使用画布格式化粒子介绍

老版的three.js提供了两种使用THML5画布格式化粒子的方法，即使用CanvasRenderer类和使用WebGLRenderer类，但是新版three.js将CanvasRenderer类移除了

所以我们讨论学习通过画布格式化粒子，只针对WebGLRenderer类，即我们创建的渲染器都是使用WebGLRenderer类。

接下来介绍一下PointsMaterial材质的属性

属性	描述
color	该属性指定粒子材质的颜色，默认值是0xFFFFFF
map	通过该属性可以在粒子上应用某种材质。例如看起来像雪花的材质
size	通过该属性指定粒子的大小，默认值是1.0
sizeAnnutation	该属性是一个布尔值，若为true表示粒子的大小由粒子到相机的距离决定，若为false表示无论粒子到相机的距离是多少，粒子都会有相同的尺寸
morphTargets	该属性是一个布尔值，指定材质是否使用morphTargets。默认值为false

2.使用HTML5画布格式化粒子

2.1创建Texture画布纹理

示例中粒子展示的是一群小怪兽，创建画布纹理就是获取小怪兽的样子，具体实现如下

// 绘制小怪兽纹理
getTexture () {
    
    
  const canvas = document.createElement('canvas')
  canvas.width = 32
  canvas.height = 32
  const ctx = canvas.getContext('2d')
  
  // 身体
  ctx.translate(-81, -84)
  ctx.fillStyle = 'orange'
  ctx.beginPath()
  ctx.moveTo(83, 116)
  ctx.lineTo(83, 102)
  ctx.bezierCurveTo(83, 94, 89, 88, 97, 88)
  ctx.bezierCurveTo(105, 88, 111, 94, 111, 102)
  ctx.lineTo(111, 116)
  ctx.lineTo(106.333, 111.333)
  ctx.lineTo(101.666, 116)
  ctx.lineTo(97, 111.333)
  ctx.lineTo(92.333, 116)
  ctx.lineTo(87.666, 111.333)
  ctx.lineTo(83, 116)
  ctx.fill()

  // 眼睛
  ctx.fillStyle = 'white'
  ctx.beginPath()
  ctx.moveTo(91, 96)
  ctx.bezierCurveTo(88, 96, 87, 99, 87, 101)
  ctx.bezierCurveTo(87, 103, 88, 106, 91, 106)
  ctx.bezierCurveTo(94, 106, 95, 103, 95, 101)
  ctx.bezierCurveTo(95, 99, 94, 96, 91, 96)
  ctx.moveTo(103, 96)
  ctx.bezierCurveTo(100, 96, 99, 99, 99, 101)
  ctx.bezierCurveTo(99, 103, 100, 106, 103, 106)
  ctx.bezierCurveTo(106, 106, 107, 103, 107, 101)
  ctx.bezierCurveTo(107, 99, 106, 96, 103, 96)
  ctx.fill()

  // 眼球
  ctx.fillStyle = 'blue'
  ctx.beginPath()
  ctx.arc(101, 102, 2, 0, Math.PI * 2, true)
  ctx.fill()
  ctx.beginPath()
  ctx.arc(89, 102, 2, 0, Math.PI * 2, true)
  ctx.fill()

  const texture = new THREE.Texture(canvas)
  texture.needsUpdate = true
  return texture
}

2.2 创建粒子材质

使用THREE.PointsMaterial类创建粒子材质和创建其他材质一样。不过我们需要将上面的创建纹理的函数赋值给材质的map属性，具体看示例代码

// 创建粒子材质
const material = new THREE.PointsMaterial({
    
    
  size: this.properties.size.value,
  transparent: this.properties.transparent,
  map: this.getTexture(),
  opacity: this.properties.opacity.value,
  vertexColors: this.properties.vertexColors,
  sizeAttenuation: this.properties.sizeAttenuation,
  color: this.properties.color
})

2.2 创建Points对象并添加到场景

// 创建粒子系统对象
this.points = new THREE.Points(geom, material)
// 将粒子系统对象添加到场景
this.scene.add(this.points)

3.demo效果

4.demo代码

<template>
  <div>
    <div id="container"></div>
    <div class="controls-box">
      <section>

        <el-row>
          <el-checkbox v-model="properties.transparent" @change="redraw">transparent</el-checkbox>
        </el-row>
        <el-row>
          <div v-for="(item,key) in properties" :key="key">
            <div v-if="item&&item.name!=undefined">
              <el-col :span="8">
                <span class="vertice-span">{
    
    {
    
    item.name}}</span>
              </el-col>
              <el-col :span="13">
                <el-slider v-model="item.value" :min="item.min" :max="item.max" :step="item.step" :format-tooltip="formatTooltip" @change="redraw"></el-slider>
              </el-col>
              <el-col :span="3">
                <span class="vertice-span">{
    
    {
    
    item.value}}</span>
              </el-col>
            </div>
          </div>
        </el-row>
        <el-row>
          <el-checkbox v-model="properties.vertexColors" @change="redraw">vertexColors</el-checkbox>
        </el-row>
        <el-row>
          <el-col :span="8" class="label-col"><label> color</label></el-col>
          <el-col :span="16">
            <div @click="inputClick">
              <el-input :value="properties.color"></el-input>
            </div>
            <div v-show="isShowColors" class="color-select-layer">
              <sketch-picker v-model="properties.color" @input="colorChange"></sketch-picker>
            </div>
          </el-col>
        </el-row>
        <el-row>
          <el-checkbox v-model="properties.sizeAttenuation" @change="redraw">sizeAttenuation</el-checkbox>
        </el-row>
        <el-row>
          <el-checkbox v-model="properties.rotateSystem" @change="redraw">rotateSystem</el-checkbox>
        </el-row>

      </section>

    </div>
  </div>
</template>

<script>
import * as THREE from 'three'
import {
    
     OrbitControls } from 'three/examples/jsm/controls/OrbitControls.js'
import {
    
     Sketch } from 'vue-color'
export default {
    
    
  components: {
    
    
    'sketch-picker': Sketch
  },
  data () {
    
    
    return {
    
    
      properties: {
    
    
        size: {
    
    
          name: 'size',
          value: 9,
          min: 0,
          max: 20,
          step: 0.1
        },
        opacity: {
    
    
          name: 'opacity',
          value: 0.6,
          min: 0,
          max: 1,
          step: 0.1
        },
        transparent: true,
        vertexColors: true,
        sizeAttenuation: true,
        rotateSystem: true,
        color: '#ccffcc'
      },
      isShowColors: false,
      points: null,
      camera: null,
      scene: null,
      renderer: null,
      controls: null
    }
  },
  mounted () {
    
    
    this.init()
  },
  methods: {
    
    
    formatTooltip (val) {
    
    
      return val
    },
    inputClick () {
    
    
      this.isShowColors = !this.isShowColors
    },
    colorChange (val) {
    
    
      this.properties.color = val.hex
      this.redraw()
    },
    // 初始化
    init () {
    
    
      this.createScene() // 创建场景
      this.createParticles() // 创建粒子系统
      this.createCamera() // 创建相机
      this.createRender() // 创建渲染器
      this.createControls() // 创建控件对象
      this.render() // 渲染
    },
    // 创建场景
    createScene () {
    
    
      this.scene = new THREE.Scene()
    },
    // 创建粒子系统
    createParticles () {
    
    
      // 创建几何体
      const geom = new THREE.Geometry()
      // 创建粒子材质
      const material = new THREE.PointsMaterial({
    
    
        size: this.properties.size.value,
        transparent: this.properties.transparent,
        map: this.getTexture(),
        opacity: this.properties.opacity.value,
        vertexColors: this.properties.vertexColors,
        sizeAttenuation: this.properties.sizeAttenuation,
        color: this.properties.color
      })

      const range = 500
      for (let i = 0; i < 5000; i++) {
    
    
        const particle = new THREE.Vector3(
          Math.random() * range - range / 2,
          Math.random() * range - range / 2,
          Math.random() * range - range / 2
        )
        // 给几何体添加顶点坐标
        geom.vertices.push(particle)
        const color = new THREE.Color(0xffffff * Math.random())
        // 给几何体添加顶点颜色
        geom.colors.push(color)
      }

      // 创建粒子系统对象
      this.points = new THREE.Points(geom, material)
      this.points.name = 'particles'
      // 将粒子系统对象添加到场景
      this.scene.add(this.points)
    },
    // 绘制小怪兽纹理
    getTexture () {
    
    
      const canvas = document.createElement('canvas')
      canvas.width = 32
      canvas.height = 32

      const ctx = canvas.getContext('2d')
      // 身体
      ctx.translate(-81, -84)

      ctx.fillStyle = 'orange'
      ctx.beginPath()
      ctx.moveTo(83, 116)
      ctx.lineTo(83, 102)
      ctx.bezierCurveTo(83, 94, 89, 88, 97, 88)
      ctx.bezierCurveTo(105, 88, 111, 94, 111, 102)
      ctx.lineTo(111, 116)
      ctx.lineTo(106.333, 111.333)
      ctx.lineTo(101.666, 116)
      ctx.lineTo(97, 111.333)
      ctx.lineTo(92.333, 116)
      ctx.lineTo(87.666, 111.333)
      ctx.lineTo(83, 116)
      ctx.fill()

      // 眼睛
      ctx.fillStyle = 'white'
      ctx.beginPath()
      ctx.moveTo(91, 96)
      ctx.bezierCurveTo(88, 96, 87, 99, 87, 101)
      ctx.bezierCurveTo(87, 103, 88, 106, 91, 106)
      ctx.bezierCurveTo(94, 106, 95, 103, 95, 101)
      ctx.bezierCurveTo(95, 99, 94, 96, 91, 96)
      ctx.moveTo(103, 96)
      ctx.bezierCurveTo(100, 96, 99, 99, 99, 101)
      ctx.bezierCurveTo(99, 103, 100, 106, 103, 106)
      ctx.bezierCurveTo(106, 106, 107, 103, 107, 101)
      ctx.bezierCurveTo(107, 99, 106, 96, 103, 96)
      ctx.fill()

      // 眼球
      ctx.fillStyle = 'blue'
      ctx.beginPath()
      ctx.arc(101, 102, 2, 0, Math.PI * 2, true)
      ctx.fill()
      ctx.beginPath()
      ctx.arc(89, 102, 2, 0, Math.PI * 2, true)
      ctx.fill()

      const texture = new THREE.Texture(canvas)
      texture.needsUpdate = true
      return texture
    },
    // 创建相机
    createCamera () {
    
    
      const element = document.getElementById('container')
      const width = element.clientWidth // 窗口宽度
      const height = element.clientHeight // 窗口高度
      const k = width / height // 窗口宽高比
      // PerspectiveCamera( fov, aspect, near, far )
      this.camera = new THREE.PerspectiveCamera(35, k, 0.1, 1000)
      this.camera.position.set(-80, 60, 40) // 设置相机位置

      this.camera.lookAt(new THREE.Vector3(10, 0, 0)) // 设置相机方向
      this.scene.add(this.camera)
    },
    // 创建渲染器
    createRender () {
    
    
      const element = document.getElementById('container')
      this.renderer = new THREE.WebGLRenderer()
      this.renderer.setSize(element.clientWidth, element.clientHeight) // 设置渲染区域尺寸
      this.renderer.shadowMap.enabled = true // 显示阴影
      this.renderer.shadowMap.type = THREE.PCFSoftShadowMap
      this.renderer.setClearColor(0x3f3f3f, 1) // 设置背景颜色
      element.appendChild(this.renderer.domElement)
    },

    // 重新绘制
    redraw () {
    
    
      this.scene.remove(this.points)
      this.createParticles()
    },

    render () {
    
    
      if (this.properties.rotateSystem) {
    
    
        this.points.rotation.y += 0.01
      }
      this.renderer.render(this.scene, this.camera)
      requestAnimationFrame(this.render)
    },
    // 创建控件对象
    createControls () {
    
    
      this.controls = new OrbitControls(this.camera, this.renderer.domElement)
    }
  }
}
</script>

<style>
#container {
    
    
  position: absolute;
  width: 100%;
  height: 100%;
}
.controls-box {
    
    
  position: absolute;
  right: 5px;
  top: 5px;
  width: 300px;
  padding: 10px;
  background-color: #fff;
  border: 1px solid #c3c3c3;
}
.label-col {
    
    
  padding: 8px 5px;
}
.color-select-layer {
    
    
  position: relative;
  left: -20px;
  padding: 15px 0;
}
.vertice-span {
    
    
  line-height: 38px;
  padding: 0 2px 0 10px;
}
</style>