Faster fractals grow in your Atari. By Douglas Skrecky
Watch elegant fractal patterns come alive onscreen at top speed with this fast and friendly ACTION! program. It works on 8-bit Atari computers with at least 48K memory and disk drive. If you are typing in the program, you will need the ACTION! cartridge from ICD. But if you own this month's Antic Disk, you will find a version that runs without the special cartridge.
In May, 1987, Antic published my fractal generating program, Dot Hopper. That program used floating point arithmetic and was written in BASIC. Consequently, it was quite slow.
After playing with the ACTION! cartridge for awhile, I realized that floating point calculations were completely unnecessary for this language. Between ACTION!'S inherent speed and integer arithmetic, I found that the program could be made to run many times faster than in BASIC. Using ACTION!, the Atari could generate fractal patterns in seconds. The fractals appear to "come alive" and grow right before your eyes.
You don't have to know anything about the mathematics of fractal geometry to appreciate these elegant patterns. Some am startlingly organic, others are reminiscent of snowflakes and lace. If you enjoy the beauty of fractal imagery, you'll have fun with this program.
Type in Listing 1, SUPERHOP.ACT, and save a copy to disk before you start the program. Antic Disk users don't need the ACTION! language cartridge to enjoy Superhop ACTION!. A runtime version, SUPERHOP.EXE, is on this month's disk. (As is usually the case, this runtime ACTION! translation would be too long to print as a typein listing.) Copy SUPERHOP.EXE to another disk that has been formatted with DOS 2 or DOS 2.5, and make sure the disk contains a DOS.SYS file. Rename SUPERHOP.EXE to AUTORUN.SYS so that the program will load and run automatically.
To start growing fractals, turn off your Atari and insert your prepared Superhop ACTION! disk. Remove all cartridges (XL and XE owners press [OPTION] and turn on your computer. Superhop ACTION! will load and run automatically.
When the program runs, it first presents the main menu, which lists the various commands and options. You can return to this menu from any other screen simply by pressing [M].
Pressing [D] activates the demo mode, which generates successive fractals through 15000 iterations each (it doesn't take very long). Demo mode continues generating fractals until you press the [M] key to return to the menu, or press [C] to generate a single fractal.
While fractals are being generated in either Demo or Create mode, pressing the cursor keys (you don't have to press the [CONTROL] key with them) will shift the fractal so that you can view a different portion on the screen. However, the fractal is erased from the screen and the growth process must begin all over again--with the same pattern. The patterns are generated fast enough that this isn't a big inconvenience.
You may use the [>] key to "zoom in" on a portion of the fractal, enlarging it on the screen. The [<] key "zoom out". These keys also start the fractal growth process over again.
Pressing [C] changes the pattern. To see some of the possible patterns, try letting each pattern grow for only a few seconds before pressing [C] again. Then if a new pattern looks particularly interesting you can let it grow, and see how it develops. Also, try letting patterns sit on the screen for several minutes after they seem to have stopped growing--they may surprise you.
SAVE A FRACTAL
If you see a fractal pattern you like, you can save it to disk by pressing the [S] key. Doing so will read in a disk directory and let you choose a filename to save the screen under. The fractal is saved as a 62-sector Micro-Painter compatible file. Once the image has been saved, the program will return to the pattern in progress, which continues to grow without starting over.
To convert your Micro-Painter image to Micro Illustrator format, you can use Rapid Graphics Converter in the November 1985 Antic.
To load a fractal into Superhop ACTION! press [L]. A directory of the disk in drive 1 will be displayed. Enter the filename of the fractal you want, and it will appear on the screen. (Note that the fractal does not continue to grow after it has been loaded.)
Pressing the [SPACEBAR] will turn off the screen and speed up fractal growth by about 30%, although I realize that this is not an especially useful function!
Douglas Skrecky is a maincframe programmer who currently lives in Vancouver, Canada. He likes to relax after work with his "trusty Atari 8-bit and perhaps a mug of beer."