// Sierpinski Gasket illustration
//
// The Sierpinski Gasket takes the form of a
// square that is divided into 9 regions (3
// rows, 3 columns). The middle region is
// blacked out. We repeat this divide-and-
// blackout procedure on each of the
// surrounding eight regions. If we continue
// this an infinite number of times, we end
// up with a "lacework" design that is more
// space than solid.

// Global Variables
int recursionDepth = 5; // # of times to repeat
int canvasWidth = 500;
int canvasHeight = 500;
int normalFillColor = 150; // vs. black for center regions

void setup ()
{
  size(canvasWidth, canvasHeight);
  background(0);
  fill(normalFillColor);
  
  sierpinski(recursionDepth, 0, 0, canvasWidth/3, canvasHeight/3);
println("Finished calling sierpinski");
}

// sierpinski() -- display a Sierpinski Gasket
// for a rectangle with the supplied dimensions
void sierpinski (int depth, int topLeftX, int topLeftY, int w, int h)
{
  println("Calling sierpinski with depth=" + depth);
  // Base case: If there are no more levels of
  // depth remaining, stop
  if (depth < 1)
  {
    return;
  }
  else
  {
    // Divide the rectangle into 9 regions:
    //
    //    -------------
    //    | 1 | 2 | 3 |
    //    |---|---|---|
    //    | 4 | 5 | 6 | (5 will be blacked out)
    //    |---|---|---|
    //    | 7 | 8 | 9 |
    //    -------------
    
    // Calculate the width and height of each
    // of the 9 regions
    
//    int regionWidth = (w - topLeftX)/3;
//    int regionHeight = (h - topLeftY)/3;
//println("regionWidth: " + regionWidth + " regionHeight: " + regionHeight);    
    
//    if (regionWidth > 0 && regionHeight > 0)
//    {
    
    // For each region, draw a filled-in rectangle
    // and then sierpinski-ize it

    // Draw region 1
    println("Drawing region 1, depth: " + depth);
    fill(150);
    rect(topLeftX, topLeftY, w, w);
    sierpinski(depth-1, topLeftX, topLeftY, w/3, w/3);
    
    // Draw region 2
    println("Drawing region 2, depth: " + depth);
    fill(150);
    rect(topLeftX+w, topLeftY, w, h);
    sierpinski(depth-1, topLeftX+w, topLeftY, w/3, h/3);
    
    // Draw region 3
    println("Drawing region 3, depth: " + depth);
    fill(150);
    rect(topLeftX+(2*w), topLeftY, w, h);
    sierpinski(depth-1, topLeftX+(2*w), topLeftY, w/3, h/3);
    
    // Draw region 4
    println("Drawing region 4, depth: " + depth);
    fill(150);
    rect(topLeftX, topLeftY+h, w, h);
    sierpinski(depth-1, topLeftX, topLeftY+h, w/3, h/3);
    
    // Draw region 5
    println("Drawing region 5, depth: " + depth);
    fill(0);
    rect(topLeftX+w, topLeftY+h, w, h);
    
    // Draw region 6
    println("Drawing region 6, depth: " + depth);
    fill(150);
    rect(topLeftX+(2*w), topLeftY+h, w, h);
    sierpinski(depth-1, topLeftX+(2*w), topLeftY+h, w/3, h/3);
    
    // Draw region 7
    println("Drawing region 7, depth: " + depth);
    fill(150);
    rect(topLeftX, topLeftY+(2*h), w, h);
    sierpinski(depth-1, topLeftX, topLeftY+(2*h), w/3, h/3);
    
    // Draw region 8
    println("Drawing region 8, depth: " + depth);
    fill(150);
    rect(topLeftX+w, topLeftY+(2*h), w, h);
    sierpinski(depth-1, topLeftX+w, topLeftY+(2*h), w/3, h/3);
    
    // Draw region 9
    println("Drawing region 9, depth: " + depth);
    fill(150);
    rect(topLeftX+(2*w), topLeftY+(2*h), w, h);
    sierpinski(depth-1, topLeftX+(2*w), topLeftY+(2*h), w/3, h/3);
  }
}