9/07/1991

M A E L S T R 0 M ver. 2.1

Copyright(c) 1990, 1991 James Harford


Description: VGA display awash with multicolored currents, rapids,
and eddies ..This is the COLOR version!

Restrictions: MAELSTR0M is "freeware". It may be copied and distributed
providing an unmodified copy of file MALSTR21.ZIP (9/07/91)
is included.

Requirements: VGA supporting 256K mode.

Operation: Type MAELSTRM and press Enter.
The control keys are
Esc = Quit,
"+" = Speed up animation.
"-" = Slow down animation.
"c" = Change the color scheme.
"k" = "keep" current image (see command line options
T and C below).
space bar = Begin a new image.

Optional command line parameters:

S Screensaver mode. No title and footer. The entire screen
is used to display the image.

I<0-2> Image drawing mode.

I0 = Image drawn in 3 vertical passes. First pass draws every
third horizontal scan line of image, giving user a quick
but coarse preview image. Passes two and three complete
the image.This is the default drawing mode.

I1 = Similar to I0, except that previous image is allowed
to show in the gaps left by passes one and two until
finally overwritten by pass three.This appears as
a gradual fadeover to the new image.

I2 = Image drawn in 1 vertical pass. Image gradually overwrites
previous image. Useful when high resolution is desired
at all times.

T<0-59> Display time -- number of minutes before drawing a new pattern.
The default is no limit. The current pattern may be kept
indefinitely by pressing "k" while it is being drawn or
displayed. Pressing the space bar re-activates the display time
option as specified by the "T" command-line parameter.

C Select a new color scheme when beginning a new image. This
may be overridden by pressing "k". It is re-activated by
pressing "c".

E Except for the initial vortex display, the images are derived
from equations describing the electric field surrounding a set
of stationary point charges in a two-dimensional space.There
are two families of lines in an image -- lines of electric
force, and lines of equipotential.

Each line of force begins and ends on a charge.The number of
lines meeting at a charge determines its magnitude, so each
point charge is a multiple of a fundamental unit "the line".
(It would be hard to write this program if that were not the
case!)

Each line of equipotential represents a set of points of
equal potential energy and is a closed (simple) curve.

The command parameter E forces the program to use the same
charge value for calculating lines of force as for lines of
equipotential. Otherwise, to increase visual interest,
different magnitudes are assigned to the same point charge
for the two families of lines.


L Limits the density of lines, as well as the maximum number
of lines of force meeting at a point charge. Default is 15.


F Faster drawing (by not waiting for vertical retrace). This
may result in increased flicker on some systems.

Credit:

MAELSTROM was created using Borland's Turbo Pascal version 6.0 and
uses VGA256.BGI from Borland''s BGI Toolbox 1.0.

Inspired by the display of an impressive screensaver product for the
Macintosh called Flowfazer, by Utopia Grokware, Sausalito, CA.

Thanks also to Jon Harford for his assistence.

Comments welcome! Send to Jim Harford, CompuServe ID 70313,750.