Sparkle.txt

"use strict";

export default class Sparkle {

   static configMeta = {
      params: {
         sparking: {
            type: 'number',
            description: 'Indicates the chance (out of 255) that a spark will ignite. A higher value makes the fire more active.',
            default: 128,
            min: 1,
            max: 255
         },
         decay: {
            type: 'number',
            description: 'The amount by which the sparks will diminish at each tick. Higher numbers fade quicker.',
            default: 2,
            min: 1,
            max: 255
         },
         sideLum: {
            type: 'number',
            description: 'How bright to make the leds on the side of a new spark.',
            default: 100,
            min: 0,
            max: 255
         }
      }
   }

   #frame = [];
   #sparking = Sparkle.configMeta.params.sparking.default;
   #sideLum = Sparkle.configMeta.params.sideLum.default;
   #decay = Sparkle.configMeta.params.decay.default;

   setNumLeds(numLeds) {
      this.#frame = [];
      for (let i = 0; i < numLeds; i++) {
         this.#frame.push([255, 0, 0, 0]);
      }
   }

   setConfig(config) {
      this.#sparking = config.sparking ?? Sparkle.configMeta.params.sparking.default;
      this.#sideLum = config.sideLum ?? Sparkle.configMeta.params.sideLum.default;
      this.#decay = config.decay ?? Sparkle.configMeta.params.decay.default;
   }

   nextFrame() {
      const sparking = this.#sparking;
      const sideLum = this.#sideLum;
      const decay = this.#decay;
      const frame = this.#frame;

      for (let i = 0; i < frame.length; i++) {
         const rgb = frame[i];
         addLum(rgb, -decay);
      }

      const numSparkles = getRandomInt(255 + 1) < sparking ? 1 : 0;

      for (let i = 0; i < numSparkles; i++) {
         const pos = getRandomInt(frame.length);

         addLum(frame[pos], 255);
         if (pos == 0) {
            addLum(frame[frame.length - 1], sideLum);
            addLum(frame[1], sideLum);
         } else if (pos === frame.length - 1) {
            addLum(frame[pos - 1], sideLum);
            addLum(frame[0], sideLum);
         } else {
            addLum(frame[pos - 1], sideLum);
            addLum(frame[pos + 1], sideLum);
         }
      }

      return frame;
   }

}

function addLum(rgb, lum) {
   rgb[1] = Math.max(0, Math.min(255, rgb[1] + lum));
   rgb[2] = Math.max(0, Math.min(255, rgb[2] + lum))
   rgb[3] = Math.max(0, Math.min(255, rgb[3] + lum))
}

function getRandomInt(maxExclusive) {
   return Math.floor(Math.random() * maxExclusive);
}