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1994-02-14
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6KB
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146 lines
FUN FRACTALS
<< by George Knight >>
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INTRODUCTION
Even if you've never generated a fractal yourself, I'm sure
you've seen many of them displayed in magazines and will know what
they look like. Use Fun Fractals to generate a few for yourself!
For the benefit of those who know nothing about it, a fractal
is a graphic image generated by using an iterative mathematical
process. Impressed? No? Well, it doesn't really matter anyway
because it's the result that counts. Although some mathematicians
regard all of this very seriously and see applications
particularly in the area of simulation, I believe that the only
significant value so far has been of an aesthetic nature.
I started this project just to find out what fractals are all
about and what you have here is a gathering together of the bits
that I programmed. It may be of interest especially to those who
have no experience of this sort of thing.
All programming has been in C and I have used a hires screen
whereas most other fractal generators use lores. As a consequence
of this, some of the images will take some time to render unless
you have a faster machine than my 2000. Because I am using hires,
you should be satisfied with a smaller image or use a faster
machine.
INSTALLATION
There is no special problem in installing the FunFractals
program itself; copy it wherever you want it.
To get the most from this program, you will need to copy the
freely available "reqtools.library" into your "lib" directory if
it is not yet there. This file is needed for the requesters that
are used in FunFractals. You will find all you need and more on
Fish 794.
GETTING STARTED
Double click on the FunFractals icon to open a blank screen on
which the fractals will be drawn.
Choose Render from the project menu (or press R with the right
Amiga key down) and watch a small Mandelbrot fractal generated.
If you want a larger image, choose Full or Half from the Image
Size menu and again Render. If at any time you want to abort
while rendering, press the Esc key and wait until the vertical
line being drawn is complete.
For reasons described below, the screen is not cleared
automatically; to clear it you must select Clear from the Project
menu (or press C with the right Amiga key down).
Images less than full size can be retained while new images
are drawn. Simply choose Advance from the Project menu (or use
right-Amiga-A) to move to the next position going from left to
right and then down. The frame number starting from 0 is
displayed in the screen title bar. You can have 16 quarter size
images or 4 half size images displayed at the one time.
If you want to change the colours, select Colours from the
Options menu and use the reqtools requester that opens. This
allows you to swap colours or spread colours over a range. For
further information read the docs that accompany the reqtools
programs on Fish 794.
If you want to save the displayed screen in IFF format for
input to another program, choose Save (or use right-Amiga-S) and
use the file requester to specify the destination file path and
name. This works only if you have installed "reqtools.library".
To exit FunFractals, select Quit from the Project menu (or use
right-Amiga-Q).
OTHER SETS
As well as the Mandelbrot set there are 4 Julia sets and a
routine to generate the so called Sierpinski Triangle.
To generate the Sierpinski triangle, clear the screen by
selecting Clear from the Project menu and then choose Sierpinski
from the Set menu. Use the Esc key to abort.
To run a Julia set, choose one from the set menu.
When you select a Julia set, a requester appears allowing you
to vary two parameters which can make a big difference in the
image produced. To accept the default values simply click on OK.
If you want to experiment, you would be wise to use values in the
range -2 to 2. Best results are usually obtained in the range of
-1 to 1. Click to activate the string gadget, press X with the
right-Amiga key down to clear the gadget and type in two new
values separating them with a comma.
ZOOMING
Portions of a Mandelbrot or Julia image can be magnified by
describing a square on the most recently completed image. Press
and hold down the left mouse button with the cursor at the point
which will be the top left hand corner of the new image and drag
down and right until the cursor reaches the point that will become
the new bottom right hand corner. Now release the left mouse
button.
When you now render, the square that you have described will
be blown up to the currently selected size (quarter, half or
full).
You can describe a square that is larger than the image
displayed. A larger area, not completely visible, will be reduced
to the currently selected size.
ITERATIONS
The default number of iterations is 16. This can be changed
by choosing Iterations from the Options menu. If the number is
increased more detail will be shown but rendering will be slower;
the smaller the number the smoother the image and this can be an
advantage if you want a background or if you are generating an
animation sequence.
George Knight
1 Audie Pde
Berkeley Vale 2259
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