class TailBoid extends Boid {
    ArrayList history;
    
    TailBoid() {
      super();
      history = new ArrayList();
    }
    
    TailBoid(Vector3D l, float ms, float mf) {
        super(l, ms, mf);
        history = new ArrayList();
    }
    
    Boid newBoid() {
        return new TailBoid(new Vector3D(width/2,height/2),4.0f,0.1f);
    }
    
    void drawTail() {
      Iterator iter = history.iterator();
      Vector3D tvec, lvec;
      int scolor = 0;
      
      if(history.size() > 1) {
        lvec = (Vector3D)iter.next();
        while(iter.hasNext()) {
          tvec = (Vector3D)iter.next();
          scolor+=5;
          stroke(scolor);
          if(abs(dist(lvec.x(), lvec.y(), lvec.z(), tvec.x(), tvec.y(), tvec.z())) < 10.0) 
            line(lvec.x(), lvec.y(), lvec.z(), tvec.x(), tvec.y(), tvec.z());
          lvec = tvec;
        }
      }
    }
    
    void render() {
        float theta = vel.heading2D() - radians(90);
        push();
        stroke(255, 0, 0);
        //line(loc.x(), loc.y(), loc.x() - 10*sin(theta), loc.y() + 10*cos(theta));
        fill(255, 0, 0);
        stroke(100);
        
        push();
        //println(loc.z());
        translate(loc.x(), loc.y(), loc.z());
        ellipse(0, 0, 8, 8);
        pop();
        
        if(history.size() > 40) {
          history.remove(0);
        }
        
        history.add(new Vector3D(loc.x(), loc.y(), loc.z()));
        
        this.drawTail();
        
        pop();
    }
}