nebula.js

class Nebula {
  constructor() {
    this.noise = new OpenSimplexNoise2D(Date.now());
    this.imgBlue = createGraphics(width, height);
    this.imgRed = createGraphics(width, height);

    this.xoff = 0.002;
    this.yoff = 0.002;

    this.imgBlue.loadPixels();
    this.imgRed.loadPixels();

    for (let x = 0; x < width; x++) {
      for (let y = 0; y < height; y++) {
        let n = this.noise.noise(x * this.xoff, y * this.yoff);
        let b = map(n, -1, 1, 0, 20);
        let c = color(220, 50, b);
        this.imgBlue.set(x, y, c);

        n = this.noise.noise(x * this.xoff + 10000, y * this.yoff + 10000);
        b = map(n, -1, 1, 0, 20);
        this.imgRed.set(x, y, color(5, 40, b));
      }
    }

    this.imgRed.updatePixels();
    this.imgBlue.updatePixels();
  }

  draw() {
    blendMode(LIGHTEST);
    image(this.imgBlue, 0, 0, width, height);
    image(this.imgRed, 0, 0, width, height);
    blendMode(BLEND);
  }
}