Source: particles/ambient/snow_emitter.js

  1. import ParticleEmitter from "../particle_emitter.js";
  2. import SnowParticle from "./snow_particle.js";
  3. import engine from "../../index.js";
  5. class SnowEmitter extends ParticleEmitter{
  6.     /**
  7.      * @constructor SnowEmitter
  8.      * @param {int} num - The number of particles to emit
  9.      * @param {float} lifespan - The life of the emitter
  10.      */
  11.     constructor(num, lifespan) {
  12.         super(0, 0, num);
  13.         this.mLifespan = Date.now() + lifespan;
  14.         this.mWind = 0;
  15.     }
  16.     /**
  17.      * @function getWind() - Gets the current horizontal acceleration
  18.      * @returns {float} mWind - The current horizontal acceleration
  19.      */
  20.     getWind(){
  21.         return this.mWind;
  22.     }
  23.     /**
  24.      * @function setWind() - Sets the horizontal acceleration
  25.      * @param {float} val - The new horizontal acceleration
  26.      */
  27.     setWind(val){
  28.         this.mWind = val;
  29.     }
  30.     /**
  31.      * @function emitParticles() - Creates and emits particles based on the creator function
  32.      * @param {ParticleSet} pSet - The set of particles
  33.      */
  34.     emitParticles(pSet){
  35.         let numToEmit = this.mNumRemains;
  36.         let i, p;
  37.         for (i = 0; i < numToEmit; i++) {
  38.             p = this.createSnow(this.mColorBegin, this.mColorEnd, this.mWind);
  39.             pSet.addToSet(p);
  40.         }
  41.         if (Date.now() > this.mLifespan){
  42.             this.mNumRemains = 0;
  43.         }
  44.         
  45.     }
  46.     
  47.     /**
  48.      * @function createSnow() - Creates snow particles
  49.      * @param {vec4} colorStart - The starting color
  50.      * @param {vec4} colorEnd - The ending color 
  51.      * @param {float} wind - The horizontal acceleration of the snow particles
  52.      * @returns {SnowParticle} p - The new snow particle to be added to the set
  53.      */ 
  54.     createSnow(colorStart, colorEnd, wind) {
  55.         let life = 500;
  56.         let x = (Math.random()-.5) * 200;
  57.         let y = 80 + Math.random();
  58.         let p = new SnowParticle(x, y, life);
  59.         p.setColor([colorStart[0],colorStart[1],colorStart[2],colorStart[3]]);
  60.         // size of the particle
  61.         let r = this.size + (Math.random()-.5) * this.variance;
  62.         p.setSize(r, r);
  63.         // final color
  64.         p.setFinalColor(colorEnd);
  65.         
  66.         // velocity on the particle
  67.         let fx = wind;
  68.         let fy = -10;
  69.         p.setVelocity(fx, fy);
  70.         p.setAcceleration(0, 0);
  71.         // size delta
  72.         p.setSizeDelta(1);
  73.         p.setDrag(1)
  74.         
  75.         return p;
  76.     }
  77. }
  78. export default SnowEmitter;