===================
Equipotential Graph
Version 1.31
William Benfold
(C) 1999
===================


Equipotential Graph (EG) is a program to colour-code
the space around a number of simulated point charges,
assigning colours according to electric potential.
Thus equipotentials will appear as colour boundaries.

For people who don't like/understand Physics, colour
cycling, extreme parameters, and a smooth palette can
be used to achieve hippytastic effects.



EG should be run from DOS or a DOS session within
Windows.  Parameters are passed as command line switches.




==================
=== PARAMETERS ===
==================

All parameters are optional; parameters should be preceded by
a dash (-).

Parameters are (at present):
  f<filename>:  Specifiy script file (see below)
  w<n>:  Specify screen width                   [default is 640]
  h<n>:  Specify screen height                  [default is 480]
  n<n>:  Specify number of charges (max 100)    [default is 3]
  c<n>:  Specify range of colour band (ie. size
         of potential range for each colour)    [default is 0.01]
  r   :  Rotate palette once the image is drawn
  p   :  Use a smooth palette
  v   :  Display version information
  ?   :  Display help (ie. params, etc.)

for example,
  eg -w800 -h600 -n2


The w and h parameters must specify a valid resolution, or be
omitted.

Valid resolutions include:
  320x240   (All cards)
  640x480   (Default)
  800x600   (Most SVGA cards)
  1024x768  (Many SVGA cards)
  1280x1024 (Some SVGA cards)
  1600x1200 (A few SVGA cards)
  Many other resolutions are also possible.

n.b. The parameters are all CASE SENSITIVE.




==================
===  COMMANDS  ===
==================


While the program is running:
  r       - rotate palette/stop rotation
  p       - change to pretty palette
  b       - change to boring palette (b/w)
  s       - save image to a bitmap (egdump00.bmp)
  c       - calculate potential at mouse pointer
  escape  - quit the program




==================
===  SCRIPTS  ====
==================

script files consist of the following:

PARAM statements:
  specify parameters, as for the command line options
  eg. PARAM -w800

BODY statements:

  BODY
  X=789
  Y=456
  C=-0.123

  These specify co-ordinates, and the charge of the
  particle.  Everything is case-sensitive (sorry!).

White space (eg. blank lines) can be included to pad out
a script, and comments *should* be ignored by the
program...

Script files should have the extension '.ini'




==================
===   NOTES   ====
==================


Obviously, the larger the resolution, the more slowly
the screen will be drawn.  The time taken to draw the
screen is proportional to
(number of pixels on screen) * (number of bodies).
Simple as that.

You may notice that equipotentials are not clearly
visible close to a charge.  This is due to the physical
restrictions of the monitor (the fact that the display
is not continuous, but contains a finite number of
pixels).  The chaotic effects become more pronounced when
one changes the -c parameter to extreme values.




==================
=== KNOWN BUGS ===
==================


When using the default palette, colour cycling causes
the last three quarters of the palette to become
corrupted.

There is currently no easy way to interrupt the program
whilst it is drawing the graph.