Pictures on the ST

Pictures on the ST

Post by a.. » Wed, 04 Jul 1990 00:27:04




> Well, just to add more deadweight to the dying discussion... I've just
> finished porting Fractint 12 from MSDOS to the ST, and along the way I
> added some "new" video modes as well. I added 4-color grayscale to the
> monochrome resolution, and made the medium resolution 16 colors, and
> the low resolution has a palette of 256 colors. From my calculations,
> the available palette is 512 * 511 / 2 = 130816 distinct colors. The
> 4 color grayscale is nothing wonderful to look at. Downright ugly, to
> be honest, but it would look good on a monitor with high-persistence
> phosphor. The low resolution mode looks pretty slick, though. Most of these
> fractals look really gorgeous with 256 colors.

> The trick is pretty obvious, it seems. Just use two screens, and flip the
> physical page on every vertical blank. This effectively doubles the number
> of bits per pixel, and as expected, squares the number of colors that can
> be displayed at once on screen. It also introduces an incredibly annoying
> flicker... But hey, Amigans settle for a megapixel display that updates at
> 15 hertz, 30 hertz is a lot better. Sending 4 complete screens at 15 hertz
> on the ST would give, what ... 64K displayable colors out of, oh... 36 bits
> worth of palette. Not that it'd be incredibly worthwhile.... You'd really
> need the same kind of monitor that the Amigans use - an intelligent one
> that assembles the video frames in an internal buffer.

> Going to monochrome is a slightly different story. If you just use two screens
> and flip back and forth between them, you'll get dark, half-light, and light.
> To get 4 distinct levels of grayscale, or to make the significant bits really
> significant, you have to display them onscreen for a longer period of time.
> But that's pretty easy too... So, the 70 hertz monochrome video is split up
> into a low-significance image sent for one-third of the time, or 23.3 hertz,
> and the high-significance image is sent at 47 hertz. The flicker here is
> really really noticable. Anything slower than 30 hertz will be, of course.
> Turning the brightness down or getting a monitor with high-persistence
> phosphor would cure that problem....

> Ok, I guess I've rambled long enough. I've had a lot of fun getting this code
> working, and I personally think the doubled video modes are kinda neat, even
> if the monochrome flicker is as obnoxious as a fluorescent light...

> Now... If you're really really crazed, you can do vertical blank image switching
> *and* horizontal scan palette switching at the same time. I don't think it's
> really practical for general purpose drawing, or for drawing fractals either,
> for that matter. Limiting color selections on a per-scanline basis just seems
> like too much hassle to deal with. But if you wanted to try it, you could
> draw yourself... 256 * 3 swaps per line * 200 lines = 153600 colors per
> screen. I guess that's a bit excessive, given only 130K colors in the palette.

> SO.... I hope this discussion is really, truly dead now, so we can get to
> more interesting things. Meanwhile I'll be submitting fractint for posting
> Real Soon Now. (But sometimes, ya gotta wonder. Why are you spending all
> these cycles drawing these silly pictures???)
> --

>   ... the glass is always greener on the side ...

Hey, bud, our screens (640x200, 320x200, etc.) update at 60 frames per second.
ONLY our interlace mode updates at 30 frames per sec.  DON'T even start!!!

 ALso, we have a blitter and many co-proc's and the ONLY "co-processor" YOU
have is a DMA controller, BIG DEAL!  Later

------------------------------------------------------------------------

=   /// Amiga!     | ^Service Engineer^        |         -or-          =

= ____& Only...    | Wright State University   |"Ouch! Quit-it." - Bart=
=                  | Dayton, Ohio              |  Depeche' Mode, Now!  =
========================================================================

 
 
 

Pictures on the ST

Post by david r watte » Wed, 04 Jul 1990 12:55:41



>Well, just to add more deadweight to the dying discussion... I've just
>finished porting Fractint 12 from MSDOS to the ST, and along the way I
>added some "new" video modes as well. I added 4-color grayscale to the

This seems pretty impressive from the discription.

Quote:>flicker... But hey, Amigans settle for a megapixel display that updates at
>15 hertz, 30 hertz is a lot better. Sending 4 complete screens at 15 hertz

This is incorrect.  The Amiga monitors refresh at 60Hz, all the time.
The screens with Xx400 and greater are interlaced which gives an apparent
refresh rate of 30Hz.  1/60th for each of 2 fields making 1 full image
refresh at 1/30th.  
The 1200x400 and greater mode still refreshes at 30Hz, with each pixel having
half as much data letting you use 4 colors.

15Hz would be unusable!!!



 
 
 

Pictures on the ST

Post by Howard C » Wed, 04 Jul 1990 15:14:29



>Hey, bud, our screens (640x200, 320x200, etc.) update at 60 frames per second.
>ONLY our interlace mode updates at 30 frames per sec.  DON'T even start!!!
> ALso, we have a blitter and many co-proc's and the ONLY "co-processor" YOU
>have is a DMA controller, BIG DEAL!  Later
>------------------------------------------------------------------------

>=   /// Amiga!     | ^Service Engineer^        |         -or-          =

>= ____& Only...    | Wright State University   |"Ouch! Quit-it." - Bart=
>=                  | Dayton, Ohio              |  Depeche' Mode, Now!  =
>========================================================================

Nice job of cutting down on the quotes there, "bud." Note that I said on a
so-called megapixel display. I have it on good authority that the 2024 monitor,
which displayes 1024x800 pixels, is only redrawn at 15 hertz. Granted, it's
a fair amount of work getting 800K pixels onto a screen, but this display
will only spit out 4 gray levels for all that time & effort spent in
interleaving frames. My "garbage" Atari with "no coprocessors" puts out
an 800x500 monochrome display at 70 hertz. For 4 graylevels I drop down to
35 hertz or so. For me to stoop to the slow redraw speed the Amiga spits out
I can gain another frame time, for 16 gray levels. And this is on a stock
Atari monochrome monitor, not some jazzed up $700 "megapixel" tube.

I didn't bring this up to dump on your machine, I was merely quoting a figure
for the sake of comparison. No need for an antagonistic attitude...

[But since you brought it up ... *One* DMA controller is more than adequate,
given a powerful enough selection of devices attached to it. In my case, I
happen to have a NeXT box attached to my ST, and I've found it pretty adequate
for most of my multiprocessing needs.]
--

  one million data bits stored on a chip, one million bits per chip
        if one of those data bits happens to flip,
                one million data bits stored on the chip...

 
 
 

Pictures on the ST

Post by Joe O'Hara - Product Assuran » Wed, 04 Jul 1990 11:55:59




>> You'd really
>> need the same kind of monitor that the Amigans use - an intelligent one
>> that assembles the video frames in an internal buffer.

If I read you correctly here, Howard, you're under a misconception: the
standard monitors used on Amigas are not intelligent. They are analog RGB,
NTSC or PAL compatible (depending on country). You may be referring to the
use of multiscan monitors in conjunction with de-interlacing video cards which
buffer interlaced scan lines in local RAM before sending the signal to the
monitor to remove the flicker inherent in interlaced NTSC/PAL signals.

Quote:

>Hey, bud, our screens (640x200, 320x200, etc.) update at 60 frames per second.
>ONLY our interlace mode updates at 30 frames per sec.  DON'T even start!!!

> ALso, we have a blitter and many co-proc's and the ONLY "co-processor" YOU
>have is a DMA controller, BIG DEAL!  Later

Please, Amiga owners, be polite when visiting other groups. There's no need
to start flame wars over differences in various system designs. Leave
religious fervor in the realm of metaphysics.
--
==========================================================================
  Joe O'Hara                ||      Disclaimer: I didn't say that!
  Commodore Electronics Ltd ||
  Product Assurance         || "I never lie when I have sand in my shoes."
  Systems Evaluation Group  ||             - Geordi LeForge, Star Trek TNG
==========================================================================
 
 
 

Pictures on the ST

Post by GRIG.. » Wed, 04 Jul 1990 13:33:23


Are all Amigans so paranoid that the Atari might have its strengths, too, that
you all read atari.st just to make sure no one likes their machine?  Fact
correction is OK, but the Amiga/ST flame war is DEAD.  Don't start it again --
it's what kept us and still keeps us from seriously challenging IBM/Apple.
Both machines were rushed to market in buggy versions to compete with each
other, and both user communities have flamed each other instead of enjoying
their systems.  Capishe?
-grigsby, a 5 year veteran (now conscientious objector) to this particular war.
 
 
 

Pictures on the ST

Post by SPL.. » Thu, 05 Jul 1990 03:38:47



Product Assurance) says:
Quote:

>Please, Amiga owners, be polite when visiting other groups. There's no need
>to start flame wars over differences in various system designs. Leave
>religious fervor in the realm of metaphysics.
>--
>==========================================================================
>  Joe O'Hara                ||      Disclaimer: I didn't say that!
>  Commodore Electronics Ltd ||
>  Product Assurance         || "I never lie when I have sand in my shoes."
>  Systems Evaluation Group  ||             - Geordi LeForge, Star Trek TNG
>==========================================================================

Thank you, Joe.  That should be worth a Nobel Peace Prize.  ;-)
Kinda funny, what with Communism in decline, the environment a mess, the
drug problem, etc., etc., that we get all hyped over how many MegaFroznits
our monitors run at, eh?  A little cooperation amd respect would go a long
way.  (Besides, we _should_ be beating up on MS-DOS users! ;-)


 
 
 

Pictures on the ST

Post by Dave Hayn » Sat, 07 Jul 1990 04:52:54



>The trick is pretty obvious, it seems. Just use two screens, and flip the
>physical page on every vertical blank. This effectively doubles the number
>of bits per pixel, and as expected, squares the number of colors that can
>be displayed at once on screen. It also introduces an incredibly annoying
>flicker... But hey, Amigans settle for a megapixel display that updates at
>15 hertz, 30 hertz is a lot better.

You're confused about the Amiga megapixel display.  While it's true that the
entire display is logically updated at either 10Hz or 15Hz (selectable), the
actual video refresh rate (eg, will it flicker?) is 60Hz in the 1008x800x2
mode, and 50Hz in the 1008x1024x2 mode.  You don't see any flicker on these
displays.  But they're not suitable, in the high resolution modes, for real
time on screen animation.  Not that anyone using a monochrome display is all
that concerned about animation anyway.  The simple case of the mouse pointer
"animation" is handled by "mouse-tracking", where the quadrant or sextant of
the logical screen containing the mouse pointer is updated more often.  Note
that, to the system, the screen looks just like you'd expect a megapixel
screen to look, it's only the actual screen driver that must perform any
special tricks to display on one of these monitors.


>  ... the glass is always greener on the side ...

--
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
        "I have been given the freedom to do as I see fit" -REM