FlowFieldRunner runner = new FlowFieldRunner();

void setup()
{
    //size(1800, 1000);
    size(600, 600);
    sample00();
}

void draw()
{
    runner.update();
}

void keyPressed() {
    println(" key " + key + " pressed");

    if (key == 's')
        {
        String fn = "captures/" + runner.sampleName  + ".png";
        save(fn);
    }

}

void sample00() {
    background(color(219, 237, 243));

    NoiseGenerator ngen = new NoiseGenerator(0.01, 0.5);
    ngen.setNoiseOctaveParam(3, 0.3);

    runner.sampleName = "sample00";
    runner.addLayer(new ParticlesLayer(10000,600, color(40, 49, 73), ngen) {
        public void draw(Particle p)
        {
            strokeWeight(1);
            stroke(p.c, 5);
            line(p.prev.x, p.prev.y, p.pos.x, p.pos.y);
        }
    });
}


class FlowFieldRunner
{
    ArrayList<ParticlesLayer> layers;
    ParticlesLayer currentLayer;
    int currentLayerIndex = -1;
    boolean start = true;
    String sampleName = "<none>";

    FlowFieldRunner()
        {
        layers = new ArrayList<ParticlesLayer>();
    }

    void addLayer(ParticlesLayer pl)
        {
        if (currentLayerIndex == -1)
            {
            currentLayerIndex = 0;
            currentLayer = pl;
        }

        layers.add(pl);
    }

    void update()
        {
        if (start)
            {
            this.start = false;
            println("Layer " + (currentLayerIndex + 1) + " started");
            currentLayer.init();
        }

        if (currentLayer.dead)
            {
            if (currentLayerIndex < layers.size() - 1)
                {
                println("Layer " + (currentLayerIndex + 1) + " done");
                currentLayerIndex++;
                println("Layer " + (currentLayerIndex + 1) + " started");
                currentLayer = layers.get(currentLayerIndex);
                currentLayer.init();
                //currentLayer.update();
            }
            else {
                println("Layer " + (currentLayerIndex + 1) + " done");
                noLoop();
                println("All layers drawn :-)");
            }
        }
        else {
            // updatecurrent layer
            currentLayer.update();
        }
    }

}

class ParticlesLayer {
  boolean dead = false;
  ArrayList<Particle> particles;
  int deadCount;
  int aliveCount;
  int lifeTime;
  NoiseGenerator noiseGenerator;
  color c;

  ParticlesLayer(int count, int lifeTime, color c, NoiseGenerator noiseGenerator)
  {
    this.deadCount = 0;
    this.aliveCount = count;
    this.noiseGenerator = noiseGenerator;
    this.lifeTime = lifeTime;
    this.c = c;

    particles = new ArrayList<Particle>();
    for( int x = 0; x < count; x++)
    {
      particles.add( new Particle( new PVector(-100+random(width+200), -100+random(height+200)) , this.lifeTime, this.c, this.noiseGenerator));
    }
  }

  void init()
  {
    this.noiseGenerator.init();
  }

  void update()
  {
    if(dead) return;

    for( int x = 0; x < aliveCount; x++)
    {
      Particle p = particles.get(x);
      if( !p.dead)
      {
        p.update();
        this.draw(p);
        if( p.dead)
        {
          deadCount++;
        }
      }
    }

    if( deadCount == aliveCount)
    {
      //println("All particles of this layer are dead");
      dead = true;
    }

    noiseGenerator.update();
  }

  void draw( Particle p)
  {
    // to be override to customize drawing
  }
}