home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Frozen Fish 1: Amiga
/
FrozenFish-Apr94.iso
/
bbs
/
alib
/
d7xx
/
d785
/
scrntst.lha
/
ScrnTst
/
ScrnTst.doc
< prev
next >
Wrap
Text File
|
1992-12-23
|
3KB
|
63 lines
ScrnTst.doc
In chapter 30 of his book "Computers and the Imagination" (publ'd 1991)
Clifford Pickover discusses a few useful computer applications of the MOIRE
pattern effect. One use is to render more readily observable any
'non-linearity or periodicty' in the successive beam sweeps across and down
the computer screen. For example the spacing of successive sweeps may not be
uniform. In principle, such irregularities in the vertical dimension could be
seen by having the computer draw a series of simple horizontal lines, but
Pickover maintains that defects are more visible by crossing these with a
second series of lines set at a rather small angle to the first (An example
of a moire effect). This results in a set of vertical bars showing on screen,
which will display slight waviness (sine-like curves) if non-uniformities
are present. Note that this applies only to the VERTICAL dimension of beam
motion. Such defects are correctable, incidentally, by manipulating the
monitor yoke controls.
On the assumption that beam irregularities ACROSS the screen might be
detected by, in effect, rotating 90 degrees both sets of lines, I have
programmed this variation as well.
PROGRAM OPERATION is simple. No options or conditions are required. It may
be started from the WorkBench or CLI. Menu selection permits presenting at
will either image (vertical test and horizontal test). There is also a 'QUIT'
selection. The program can be closed too, by clicking near the upper left
corner to expose the closewindow gadget.
************* NOTES to Version 2.0: *************
The present version (2.0) has been improved by introducing a RANGE of
angles between the two sets of lines forming each test pattern. For the
vertical test, pressing 'i' will increase the angle (4 stepwise variations)
and 'd' will decrease it. On increasing the angle, the vertical columns will
increase in number but be thinner. At the maximum, hitting 'i' will have no
effect. Similarly with 'd'.
For the horizontal test, a parallel set of operations is provided, but
using 'I' (shift i) and 'D' (shift d).
In programming the new version, I have switched to using two windows, one
for each test, instead of just one (though this results in no noticeable
effect!). Also the resolution has been changed to lores (320/200). This has
improved visibility of the horizontal test screen which was quite dark in
the earlier version.
Users may notice that in version 2.0, though the depth gadget is present
in each of the test screens, it does not respond to mouse clicking.
To get at the WB/CLI while the pgm is still active, simply use 'L-amiga m'.
****************************************
This program was written in assembler, using A68k and Blink. Though I have
V 2.04 OS installed, all functions and structure parameters employed are
based on those available with 1.3. Thus Amigans still using 1.3 should have
no trouble.
ScrnTst, V 2.0, is PD/FREEWARE. There are no restrictions on its use.
This documentary should of course accompany any distribution of the
program. Questions or comments about this work would be welcome. I can best
be reached by E-mail at AmigaNet in Wheeling,IL (708)983-6435:
bbarish@amiganet.chi.il.us