湧き出るひし形

/**
* rhombus
*
* @author aa_debdeb
* @date 2016/01/17
*/

ArrayList<Frame> frames;

void setup(){
  size(500, 500);
  smooth();
  frameRate(30);

  frames = new ArrayList<Frame>();
  frames.add(new Frame());
}

void draw(){
  background(255);
  translate(width / 2, height / 2);
  noStroke();
  fill(0);
  for(Frame frame: frames){
    for(float rad = 0; rad < TWO_PI; rad += PI / 2){
      pushMatrix();
      rotate(rad);
      beginShape();
      vertex(frame.dist, 0);
      if(frame.dist - frame.range < 0){
        vertex(0, 0);
      } else {
        vertex(frame.dist - frame.range , 0);
        vertex(0, frame.dist - frame.range);
      }
      vertex(0, frame.dist);
      endShape(CLOSE);
      popMatrix();
    }
    frame.update();
  }
  ArrayList<Frame> disappeared = new ArrayList<Frame>();
  for(Frame frame: frames){
    if(frame.dist >= 1000){
      disappeared.add(frame);
    }
  }
  for(Frame frame: disappeared){
    frames.remove(frame);
  }
  
  if(frames.isEmpty()){
    frames.add(new Frame());
  } else {
    Frame last = frames.get(frames.size() - 1);
    if(last.dist > last.range && random(1) < 0.5){
      frames.add(new Frame());
    }
  }
}

class Frame {

  float dist;
  float range;
  float speed;
  
  Frame(){
    dist = 0;
    range = map(random(1), 0, 1, 5, 20);
    speed = 5;
  }
  
  void update(){
    dist += speed;
  }
  
}