Example
Suppose that we start with a filled-in triangle. We connect the midpoints of each side and remove the middle triangle. We then repeat this process.

If we repeat this process, the shape that emerges is called the Sierpinski gasket. Notice that it exhibits self-similarity—any piece of the gasket will look identical to the whole. In fact, we can say that the Sierpinski gasket contains three copies of itself, each half as tall and wide as the original. Of course, each of those copies also contains three copies of itself.
In the following video, we present another explanation of how to generate a Sierpinski gasket using the idea of self-similarity.
https://youtu.be/vro9BUfJxTA
We can construct other fractals using a similar approach. To formalize this a bit, we’re going to introduce the idea of initiators and generators.
Example
Use the initiator and generator shown to create the iterated fractal.

This tells us to, at each step, replace each line segment with the spiked shape shown in the generator. Notice that the generator itself is made up of 4 copies of the initiator. In step 1, the single line segment in the initiator is replaced with the generator. For step 2, each of the four line segments of step 1 is replaced with a scaled copy of the generator:

This process is repeated to form Step 3. Again, each line segment is replaced with a scaled copy of the generator.

Notice that since Step 0 only had 1 line segment, Step 1 only required one copy of Step 0.
Since Step 1 had 4 line segments, Step 2 required 4 copies of the generator.
Step 2 then had 16 line segments, so Step 3 required 16 copies of the generator.
Step 4, then, would require
16⋅4=64 copies of the generator.

The shape resulting from iterating this process is called the Koch curve, named for Helge von Koch who first explored it in 1904.
Notice that the Sierpinski gasket can also be described using the initiator-generator approach.
Example
Use the initiator and generator below, however only iterate on the “branches.” Sketch several steps of the iteration.

We begin by replacing the initiator with the generator. We then replace each “branch” of Step 1 with a scaled copy of the generator to create Step 2.

Step 1, the generator. Step 2, one iteration of the generator.
We can repeat this process to create later steps. Repeating this process can create intricate tree shapes.[footnote]
http://www.flickr.com/photos/visualarts/5436068969/[/footnote]
Try It
Use the initiator and generator shown to produce the next two stages.
Answer:
Example
Create a variation on the Sierpinski gasket by randomly skewing the corner points each time an iteration is made.
Suppose we start with the triangle below. We begin, as before, by removing the middle triangle. We then add in some randomness.

We then repeat this process.

Continuing this process can create mountain-like structures. This landscape[footnote]
http://en.wikipedia.org/wiki/File:FractalLandscape.jpg[/footnote] was created using fractals, then colored and textured.
The following video provides another view of branching fractals, and randomness.
https://youtu.be/OyAL-66GkJY