Cesium火焰特效

//火焰特效
export  class FireEffect{
  constructor(viewer) {
    this.viewer=viewer
    this.viewModel={
      emissionRate: 5,
      gravity: 0.0,//设置重力参数
      minimumParticleLife: 1,
      maximumParticleLife: 6,
      minimumSpeed: 1.0,//粒子发射的最小速度
      maximumSpeed: 4.0,//粒子发射的最大速度
      startScale: 0.0,
      endScale: 10.0,
      particleSize: 25.0,
    }
    this.emitterModelMatrix = new Cesium.Matrix4()
    this.translation = new Cesium.Cartesian3()
    this.rotation = new Cesium.Quaternion()
    this.hpr = new Cesium.HeadingPitchRoll()
    this.trs = new Cesium.TranslationRotationScale()
    this.scene = this.viewer.scene
    this.particleSystem=''
    this.entity = this.viewer.entities.add({
      //选择粒子放置的坐标
      position: Cesium.Cartesian3.fromDegrees(
        116.34485552299206,
        39.99754814959118
      ),
    });
    this.init();
  }

  init(){
    const _this=this
    this.viewer.clock.shouldAnimate = true;
    this.viewer.scene.globe.depthTestAgainstTerrain = false;
    this.viewer.trackedEntity = this.entity;
    var particleSystem = this.scene.primitives.add(
      new Cesium.ParticleSystem({
        image: require('../assets/fire.png'),//生成所需粒子的图片路径
        //粒子在生命周期开始时的颜色
        startColor:  new Cesium.Color(1, 1, 1, 1),
        //粒子在生命周期结束时的颜色
        endColor: new Cesium.Color(0.5, 0, 0, 0),
        //粒子在生命周期开始时初始比例
        startScale: _this.viewModel.startScale,
        //粒子在生命周期结束时比例
        endScale: _this.viewModel.endScale,
        //粒子发射的最小速度
        minimumParticleLife: _this.viewModel.minimumParticleLife,
        //粒子发射的最大速度
        maximumParticleLife: _this.viewModel.maximumParticleLife,
        //粒子质量的最小界限
        minimumSpeed: _this.viewModel.minimumSpeed,
        //粒子质量的最大界限
        maximumSpeed: _this.viewModel.maximumSpeed,
        //以像素为单位缩放粒子图像尺寸
        imageSize: new Cesium.Cartesian2(
          _this.viewModel.particleSize,
          _this.viewModel.particleSize
        ),
        //每秒发射的粒子数
        emissionRate: _this.viewModel.emissionRate,
        //粒子系统发射粒子的时间（秒）
        lifetime: 16.0,
        //粒子系统是否应该在完成时循环其爆发
        loop: true,
        //设置粒子的大小是否以米或像素为单位
        sizeInMeters: true,
        //系统的粒子发射器
        emitter: new Cesium.ConeEmitter(Cesium.Math.toRadians(45.0)),//BoxEmitter 盒形发射器，ConeEmitter 锥形发射器，SphereEmitter 球形发射器，CircleEmitter圆形发射器
      })
    );
    this.particleSystem=particleSystem;
    this.preUpdateEvent()
  }

  //场景渲染事件
  preUpdateEvent() {
    let _this=this;
    this.viewer.scene.preUpdate.addEventListener(function (scene, time) {
      //发射器地理位置
      _this.particleSystem.modelMatrix = _this.computeModelMatrix(_this.entity, time);
      //发射器局部位置
      _this.particleSystem.emitterModelMatrix = _this.computeEmitterModelMatrix();
      // 将发射器旋转
      if (_this.viewModel.spin) {
        _this.viewModel.heading += 1.0;
        _this.viewModel.pitch += 1.0;
        _this.viewModel.roll += 1.0;
      }
    });
  }

  computeModelMatrix(entity, time) {
    return entity.computeModelMatrix(time, new Cesium.Matrix4());
  }

  computeEmitterModelMatrix() {
    this.hpr = Cesium.HeadingPitchRoll.fromDegrees(0.0, 0.0, 0.0, this.hpr);
    this.trs.translation = Cesium.Cartesian3.fromElements(
      -4.0,
      0.0,
      1.4,
      this.translation
    );
    this.trs.rotation = Cesium.Quaternion.fromHeadingPitchRoll(this.hpr, this.rotation);

    return Cesium.Matrix4.fromTranslationRotationScale(
      this.trs,
      this.emitterModelMatrix
    );
  }

  removeEvent(){
    this.viewer.scene.preUpdate.removeEventListener(this.preUpdateEvent, this);
    this.emitterModelMatrix = undefined;
    this.translation = undefined;
    this.rotation = undefined;
    this.hpr = undefined;
    this.trs = undefined;
  }

  //移除粒子特效
  remove() {
    ()=>{return this.removeEvent()}; //清除事件
    this.viewer.scene.primitives.remove(this.particleSystem); //删除粒子对象
    this.viewer.entities.remove(this.entity); //删除entity
  }

}