Lightning - OpenProcessing

mySketch
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ArrayList<Particle> particles = new ArrayList<Particle>();
int numBolts = 1;
int timestep = 30;
​
void setup() {
  size(1112, 834);
  background(0);
  
  for (int i = 0; i < numBolts; i++) {
    particles.add(new Particle((i+1)*width/(numBolts+1), 0, random(-3,3), 5, true));
  }
}
​
void draw() {
  //noLoop();
  //background(0);
  
  //while (particles.size() > 0) {
    for (int t = 0; t < timestep; t++) {
      for (int i = particles.size() - 1; i >= 0; i--) {
        Particle p = particles.get(i);
        p.run();
        p.split();
        p.runChildren();
        if (!p.isAlive()) {
          particles.remove(p);
        }
      }
    }
  //}
}
​
class Particle {
  PVector p;
  PVector ps;
  PVector v;
  boolean alive;
  boolean isParent;
  int opacity;
  
  ArrayList<Particle> children = new ArrayList<Particle>();
  
  Particle(x, y, vx, vy, isParent) {
    p = new PVector(x, y);
    ps = new PVector(p.x, p.y);
    v = new PVector(vx, vy);
    alive = true;
    this.isParent = isParent;
    opacity = 255;
  }
​
  Particle(x, y, vx, vy, isParent, opacity) {
    p = new PVector(x, y);
    ps = new PVector(p.x, p.y);
    v = new PVector(vx, vy);
    alive = true;
    this.isParent = isParent;
    this.opacity = opacity;
  }
  
  void run() {
    stroke(255,opacity);
    if (isParent) {
      strokeWeight(3);
    } else {
      strokeWeight(1);
      opacity -= 3;
    }
    
    ps.set(p.x,p.y);
    p.add(v);
    p.add(random(-5,5),random(-1,1));
    
    line(p.x,p.y,ps.x,ps.y);
    strokeWeight(10 + (isParent*2));
    stroke(255,floor(opacity/10));
    line(p.x,p.y,ps.x,ps.y);
  }
  
  void runChildren() {
    for (int i = children.size() - 1; i >= 0; i--) {
      Particle p = children.get(i);
      p.run();
      p.split();
      p.runChildren();
    }
  }
  
  void split() {
    if (isParent) {
      if (random() < 0.04) {
        children.add(new Particle(p.x, p.y, random(-3,3), random(1,3), false, opacity));
      }
    } else {
      if (random() < 0.02) {
        children.add(new Particle(p.x, p.y, random(-3,3), random(1,3), false, opacity));
      }
    }
  }
  
  boolean isAlive() {
    if (p.y > height) {
      alive = false;
    }
    if (!isParent && opacity <= 0) {
      alive = false;
    }
    
    return alive;
  }
}
​
void mouseClicked() {
  particles.add(new Particle(random(width), 0, random(-3,3), 5, true));
}
​
void keyPressed(){save('pix.jpg');}