 Index Books FAQ Contact About Rod   # Title: Draw a skewed Sierpinski gasket with any number of corners in C# The usual way to draw a Sierpinski gasket (as a strange attractor, anyway) is to start with 3 corners. To generate a point, randomly pick a corner and move halfway between the current position and the selected corner. See Draw a Sierpinski gasket in C# for more details.

This example lets you pick corners at run time. Left-click on the form to pick at least 2 points. Then right-click to start the program running. The program uses the following code to draw the modified gasket.

// Draw 1,000 points. private void tmrDraw_Tick(object sender, EventArgs e) { // Draw points. Random rand = new Random(); using (Graphics gr = this.CreateGraphics()) { // Draw the corners. foreach (PointF pt in Corners) { gr.FillEllipse(Brushes.White, pt.X - RADIUS, pt.Y - RADIUS, 2 * RADIUS, 2 * RADIUS); gr.DrawEllipse(Pens.Blue, pt.X - RADIUS, pt.Y - RADIUS, 2 * RADIUS, 2 * RADIUS); } // Draw 1000 points. for (int i = 1; i <= 1000; i++) { int j = rand.Next(0, Corners.Count); LastPoint = new Point( (LastPoint.X + Corners[j].X) / 2, (LastPoint.Y + Corners[j].Y) / 2); gr.DrawLine(Pens.Blue, LastPoint.X, LastPoint.Y, LastPoint.X + 1, LastPoint.Y + 1); } } }

For some interesting results, try:

• Use four corners that make a rectangle.
• Use a scalene triangle.
• Use a triangle and add 4 or 5 "corners" in the same spot near the middle.
• Try other arrangements with duplicate corners.