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Julia
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1989-08-07
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JULIA - a program to explore Julia sets
=======================================
*** WARNING *** *** WARNING *** *** WARNING ***
- If you run this program from CLI, make sure the stack is set
to at least 10,000. Otherwise you will meet the GURU.
- This program uses the Math library on your WB disk, so
don't be surprised if you are asked for the WB disk when
the program starts running.
*** WARNING *** *** WARNING *** *** WARNING ***
About this program
------------------
This program can be used to explore Julia sets. Julia set
is fractal which is obtained by a computation process very
similar to the Mandelbrot set. The difference is that there
are many different Julia sets. The shape of the set is determined
by a parameter that is a complex number. This number is denoted
by 'c' and is equal to 'cx + cy*i' where 'cx' and 'cy' are
real numbers and 'i' is the square root of -1.
The shape of the Julia set changes dramatically as the number
'c' moves from inside to the outside of the Mandelbrot set.
Futhermore, most intricate pictures are produced when 'c' lies
close to the boundary of the Mandelbrot set.
Anyway, rather than me trying to explain all the math stuff,
here are some references:
"Computer Recreations", Scientific American, November 1987
- this column was dedicated to Mandelbrot and Julia sets,
it explains clearly how the computation is done.
"The Beauty of Fractals", Peitgen and Richter, Springer-Verlag
- this is a MUST HAVE book for anyone interested in fractals;
just the pictures make this book worth having, even if you
can't understand the text (that requires knowledge of some
fairly sophisticated mathematics - i.e. do you know what
Hausdorff dimension is?)
"Fractal Geometry of nature", Mandelbrot, Freeman Press
- the orginal writings of Mandelbrot on his way to creating
fractals; requires a lot of math.
Menus
-----
Here is a brief description of the menu items:
ACTIONS
START - starts computation
CONTROL - displays the 'control panel'
ZOOM - zoom in on a portion of the picture
ABOUT - displays my name etc.
SAVE IFF - save current picture to an IFF file.
QUIT - exit program
DISPLAY
TOGGLE TITLE - displays or hides the title
CLEAR SCREEN - fills the screen with background pattern
Control Panel
-------------
The control panel allows you to choose various parameters for
the computation. They are:
ITERATIONS - number of iterations per point; more iterations
get better pictures, but require more time.
COLOR DIVISOR - determines how often the color changes;
color divisor of 1 gives most color changes;
once you zoom into the picture fewer color
changes make nicer pictures.
Re (C) - the real part of the parameter C
Im (C) - the imaginary part of C
Here are some nice values of C to try:
Re (C) Im(C)
.3968 .2125
-1.75 0.0
-.74 .125
Notes
-----
A. SYMETRY
The Julia set is symetric about (0,0). The color at (x,y)
is the same as at (-x,-y). My program tries to take the
advantage of this fact to save computation time.
B. PATTERN FILL
When the screen is cleared, it is filled with a pattern. This
is so that I can see what the program is doing. You can't
see black drawn on black and I hate to sit in front of
machine and not to see something happening.
C. RESOLUTIONS
Pictures can be drawn in all resolutions available on th
Amiga. High res gives most stunning pictures (see attached
example).
D. SOURCES
I'm not uploading the sources because I'm lazy. If you
really want to see the sources, drop me a line and we
can swap disks or something.
Some legal stuff
---------------
****************************************************************
This program is PUBLIC DOMAIN, that means, you can distribute
it free of charge as long as this notice is included.
Copyright 1987 (c) by Richie Bielak
****************************************************************
This program was written using the Benchmark Modula-2
system - the best development on the Amiga yet (in my
opinion).
If you have any comments, questions, suggestions or you've
found parameters that make pretty pictures drop me a line.
You can get me:
CIS: 75716,352
PLINK: RICHIEB
USENET: ..!cmcl2!phri!dasys1!richieb
SNAIL MAIL: 526 79th St, Brooklyn, N.Y. 11209
Enjoy Richie
***EOF*EOF******************************************************