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1985-11-20
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MandelZoom 1.0 User's Guide
This program will allow you to plot the Mandelbrot set on any
Atari ST computer (high resolution monochrome, medium resolution
color, and low resolution color). Due to the large memory
requirements of this program, you must have TOS rom chips
installed in your computer. If you are using a 520ST, you may
have to remove desk accessories that use large amounts of memory
(e.g. ramdisks).
For information about the Mandelbrot set, see the references
listed later in this document.
Using the Program
After double-clicking fractal.prg, a menu bar will appear with
four menus, "desk", "file", "pixel size", and "command".
The Desk Menu
If you select the desk menu by moving the mouse near it, you can
learn about the author of the program by selecting the "About
MandelZoom 1.0" submenu. Any desk accessories can be accessed by
selecting the desk menu.
The File Menu
This menu has three submenus, "load", "save", and "quit".
Selecting the load submenu allows the user to plot a portion of
the Mandelbrot set that has been previously plotted and saved.
After a portion of the Mandelbrot set has been plotted with a
pixel size of 1 X 1, it can be saved in a disk file for later use.
(Pixel sizes are discussed later).
When you save a file, you will be in a certain resolution. After
the file is saved, it can be loaded only when you are in the same
resolution that you were in when it was saved. For example, if
you save a plot while in low-resolution mode, it can only be
loaded when you are in low-resolution mode.
Since each saved plot has a resolution associated with it, save
all high resolution files with a type of .hig (e.g. first.hig,
big.hig). Save all medium-resolution files with a type of .med,
and all low resolution files should have a type of .low.
Selecting the quit submenu terminates the program and returns you
to the GEM desktop. Always be sure to save the current plot prior
to quitting if you want to keep it!
The Pixel Size Menu
A pixel ("picture element") is a dot on a computer's screen. When
this program makes a plot, its pixels can be much larger than a
single dot. If you select a pixel size of 16 X 16, the dots
plotted by the program will be sixteen pixels wide and sixteen
pixels high. When such large dots are plotted, the resulting plot
is very crude, but is drawn quickly. Selecting a smaller pixel
size (e.g. 1 X 1) will result in better looking pictures, but they
will be drawn much more slowly. You may find it convenient to
first make a plot with large pixels, and if it looks interesting,
plot it again with smaller pixels.
A plot can only be saved as a disk file if it has been plotted
with a pixel size of 1 X 1. If a plot is made with 1 X 1 pixels
and later plotted with larger pixels, it can still be saved.
The Command Menu
A portion of the Mandelbrot set can be plotted by selecting the
plot submenu. Although plots made with small pixel size may take
a long time to finish the first time, once a plot has been done,
it can be redrawn very quickly by selecting the plot submenu again
without first decreasing the pixel size. If you got the file
total.hig with the program, you can load this file and plot the
picture if you have a monochrome system. If you got the file
total.low, it can be loaded and plotted when you are in low-
resolution mode. If you didn't get these files, you can make them
yourself. Just run MandelZoom, select a pixel size of 1 X 1,
select the plot submenu, and when the plot is complete, save it
in a file.
When a plot has been performed, there may be a portion of it that
you would like to enlarge. First select the zoom submenu. Then
place the crosshairs at the top lefthand corner of the square that
you would like to blow up. Press the left mouse button slowly.
Now repeat this process for the bottom right corner of the square.
After you have selected the square to enlarge, it will be enclosed
in dashed lines. The square enclosed in dashed lines may differ
slightly from what you expected if your two points really
described a rectangle with unequal sides.
Now that the square is shown, after a short pause you will be
asked if you still want to do the zoom. If you answer no, the
current plot will be unchanged. If you answer yes, the zoom will
start, and the current plot will be completely lost. Always save
the current plot prior to zooming if you want to have it later.
If you have decided to go through with the zoom, the chosen square
will be plotted, and its plot will take up the entire plotting
window.
Stopping a Plot Prematurely
Often after starting a plot or a zoom, one wants to stop the plot.
To do this, press and hold down the left mouse button. In a
little while you will be asked whether or not you want to stop
the plot. If you decide to stop the plot and later change
your mind, don't worry, you can still redo the plot by
selecting the plot submenu. If you stopped a plot half way through,
when you replot it, the first half will be drawn very rapidly
(so stopping a plot doesn't throw away the results of the plot).
The final submenu of the command menu is print. Selecting this
command will cause the plotting window to be printed out on your
printer. In order to prevent the mouse and the menu from
appearing in the printout, the plot is first quickly redrawn.
More Information about the Mandelbrot Set
By all means read A. K. Dewdney's Computer Recreations column in
the August, 1985 Scientific American. If you are a mathematician
and can stand Benoit Mandelbrot's egotism, his "Fractal Geometry
of Nature" is the authoritative work on the subject. A program
similar to MandelZoom for the Macintosh computer is discussed in
the November, 1986 issue of "Dr. Dobb's Journal of Software
Tools".
More Information about this Program
Queries about MandelZoom should be sent to the following address.
Be sure to enclose a stamped, self-addressed envelope. If you are
not in the U.S.A., please enclose the proper number of
international reply coupons.
Eric Bergman-Terrell
Cadenza Software, Ltd.
1704 Imperial Ridge
Las Cruces, NM 88001
Enjoy the program!