FRACTINT Quick Guide

FRACTINT is a very nicely designed program which enables the user to draw and explore a large variety of fractal shapes. The principal authors are Bert Tyler, Timothy Wegner, Mark Peterson, and Pieter Branderhorst, although many others have made contributions. The authors have made their program available to anyone free of charge. It can be used on an IBM PC or compatible with virtually any kind of graphics adapter.

Starting FRACTINT :

To start FRACTINT at the MLRC, get someone to show you how to access the main menu on the ATT PC's and then select Fractals on the main menu (by pressing F). When FRACTINT starts, it displays a list of contributing authors. After memorizing this list, press any key to obtain FRACTINT 's main menu.

Trouble:

If any trouble occurs at any point, you can usually get out of it by pressing the escape key Esc, perhaps repeatedly.

Main Menu:

FRACTINT commands are usually entered by a single keystroke. The key to press is displayed after the name of the command on the menu. You can also use the cursor keys , , , and to move the highlighted area to the command you want. Pressing Enter then executes the command. When the main menu starts, the highlight is over the command select-video-mode.

Help:

Push F1 (the function key at the top left of the keyboard) at any point to get the on-line help documentation. You will be presented with a list of commands and descriptions. Other commands within the help system are given at the bottom of the screen. To leave the help system, push Esc.

Sample Run:

We will illustrate the use of FRACTINT with one example.

1. Press t to select the fractal type. A large collection of different fractal types will be displayed. You can use the cursor keys to move the highlight over the one you want. If you press F2, you will see a brief description of that type.
2. Type ls and the highlight will automatically move to the type lsystem. In general, just the first few letters are enough to select a type. Now press Enter.
3. FRACTINT now displays a lengthy list of what are called Lindenmayer systems (L-systems for short). These are fractals that are generated from a particular type of recursive recipe. Select the type KochCurve (by either using the cursor keys or typing the first few letters of the name of the type) and press Enter.
4. FRACTINT now displays the formula for this fractal and requests the order to which you wish to repeat the formula. Most fractals have a recursive structure in the sense that you repeat the same basic rules over and over to draw the fractal. The default order or number of repetitions is 2. First type 7 followed by Enter.
5. FRACTINT returns to the main menu because it wants you to select a video mode for your screen. Press Enter or Del at the main menu.
6. The possible video modes that work with our PC's are F3, F4, F10, or Shift-F1. Press any of these function keys and FRACTINT will start to draw the fractal.
7. After a minute or two, you will see the Koch Snowflake fractal (up to order 7). To see how this is generated, let's try a lower order like 0. To reenter the order, type z.
8. Then enter 0 followed by Enter. The order 0 version is just a straight horizontal line.
9. Repeat the last two steps for order 1. You now see that the middle third of the original horizontal line has been replaced by the top of an equilateral triangle. This is the general rule for this fractal.
10. Try order 2 now and you will again see every middle third of every line segment in the oder one version has been replaced by the top of an equilateral triangle.
11. You can carry out this kind of experiment for any fractal type in FRACTINT .

Quitting:

To quit, push Esc repeatedly until the program asks if you want to exit. Then answer y.