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1994-10-05
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________________________________________________________________________
/ \
| !Lissajous v1.00: Lissajous Function Plotter |
| January 1992 |
| by Mike Curnow |
\________________________________________________________________________/
Quick Start
===========
Double click on !Lissajous to load, then press menu over the icon bar icon
and select draw. The default Lissajous figure will be drawn. Use the cursor
keys to alter the plot and Return to restore the plot values. Return to the
desktop by clicking any mouse button. Click on the Lissajous icon to open
the Edit window to allow the Lissajous function to be changed.
Introduction
============
!Lissajous is a desktop application for plotting different Lissajous curves.
Lissajous curves were investigated by the man of the same name back
in 1857. They are most familiar in their appearance on oscilliscope
displays. In essence a Lissajous curve is the graphed result of a function
of SIN or COS. The variety of displays are produced by plotting different x
& y values against each other.
!Lissajous allows you to try out different functions and to dynamically
control the plot. The resulting functions can be saved and used within
!TidyDesk's screen blanker.
Draw
====
To enter draw mode, select draw from the menu or click on Draw in the Edit
panel. The screen is cleared and the plot commences. Use the following keys
to control the plot:
⇦ decreases the x plot
⇨ increases the x plot
⇩ decreases the y plot
⇧ increases the y plot
Return restores the x/y values to their settings
Press any mouse button to exit the drawing mode.
Edit
====
To enter edit mode, click on the !Lissajous icon, or select Edit from the
menu. Click on a field to enter input mode. The title shows the name of the
Lissajous file being editted, or <new> if it has not been saved yet. There
are 3 sections on the editing panel - the source numbers and function for
the x and y axes, and the start points for each of the axes.
Data: supply the minimum and maximum values of the x/y values as input to
the function. Min and Max values may be given as simple numbers or as
expressions using BASIC's standard functions eg. 2*PI, LOG(10). The function
is made up of BASIC functions operating on the x/y value - thus x or y must
appear somewhere in the expression. The resulting value of the function you
enter is used as the value of the x/y plots. Typically functions are based
on SIN and COS, but other functions can also be used.
Setting the Y Data 'Same as X' button on makes the Y data values the same as
X and prevents you entering data into the Y Data fields.
Start Point: !Lissajous does not continuously evaluate the functions, but
pre-calculates 256 values from Min to Max. The Initial x/y values are the
index into the table of these 256 values. The values wrap around at 256, but
may be specified as negative numbers as well. The Current x/y values show
the index values after using the cursor keys during plotting, allowing you
to set new Initial x/y values.
OK: click for your input to be entered and evaluated. An error message will
be produced if the function produces an invalid number (too large or small).
Draw: Same as OK but then enters draw mode to show the resulting plot.
Cancel: discards the data and closes the Edit window.
Notes: If you press Select over OK or Draw, the Edit box will be closed, but
not if you use Adjust. Load the sample Lissajous files to see how functions
can be defined. Use the up/down cursor keys or Return to move around the
editable fields. A plot can be reversed by swapping the Min & Max values -
eg. Min=2*PI Max=0 is valid.
Saving And Loading Data
=======================
The function data can be saved by selecting Save from the menu - it operates
in the standard RiscOS way. Saved files are loaded br dragging onto the
Lissajous icon or into the Edit window. If you double click on a Lissajous
file it is loaded into !TidyDesk, not !Lissajous.
The supplied Lissajous directory contains some sample Lissajous functions.
The name of the current file is shown in the Edit panel title.
--------------------------------------------------------------------------
Extensions
----------
There are several ways you might like to extend this program.
1) Plot more points - currently 256 are plotted, but the plot mechanism is
fast enough to allow many more points to be plotted each screen refresh.
2) Multiple plots - using the same function data, different x & y index
points can be used to show the plot at different phases.
3) Colour - possible in 16 or 256 colour modes, but you will need to change
the plotting mechanism.
I would be interested in seeing any successful results.
--------------------------------------------------------------------------
Copyright
---------
This software is copyrighted by Mike Curnow and IS NOT PUBLIC DOMAIN.
However permission is hereby granted for use of !Lissajous 1.00 on any
machine so long as no charges are levied for its usage. This software must
not be resold without prior consent from the author.
!Lissajous is based on an original program by Michael St Aubyn published in
Acorn User in November 1985.
Mike Curnow,
Stoneleigh
Swan Lane
Great Bourton
Banbury
OX17 1QR
SAE with all correspondance please.