float curlx = 0; 
float curly = 0; 
float f = sqrt(2)/2.; 
float deley = 10; 
float growth = 0; 
float growthTarget = 0; 
 
 
void setup() 
{ 
  size(950,450,P2D); 
  //smooth(); 
  addMouseWheelListener(new java.awt.event.MouseWheelListener() {  
    public void mouseWheelMoved(java.awt.event.MouseWheelEvent evt) {  
      mouseWheel(evt.getWheelRotation()); 
  }}); 
} 
void draw() 
{ 
  background(250); 
  stroke(0); 
  curlx += (radians(360./height*mouseX)-curlx)/deley; 
  curly += (radians(360./height*mouseY)-curly)/deley; 
  translate(width/2,height/3*2); 
  line(0,0,0,height/2); 
  branch(height/4.,17); 
  growth += (growthTarget/10-growth+1.)/deley; 
} 
 
void mouseWheel(int delta) 
{ 
  growthTarget += delta; 
} 
 
void branch(float len,int num) 
{ 
  len *= f; 
  num -= 1; 
  if((len > 1) && (num > 0)) 
  { 
    pushMatrix(); 
    rotate(curlx); 
    line(0,0,0,-len); 
    translate(0,-len); 
    branch(len,num); 
    popMatrix(); 
     
//    pushMatrix(); 
//    line(0,0,0,-len); 
//    translate(0,-len); 
//    branch(len); 
//    popMatrix(); 
    len *= growth; 
    pushMatrix(); 
    rotate(curlx-curly); 
    line(0,0,0,-len); 
    translate(0,-len); 
    branch(len,num); 
    popMatrix(); 
    //len /= growth; 
  } 
}