Extended graphics on the IIgs (?)

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Eric Mulholland

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Jan 18, 1991, 8:57:00 AM1/18/91
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In article <11...@darkstar.ucsc.edu> unk...@ucscb.UCSC.EDU (The Unknown User) writes:
>In article <1991Jan18...@gacvx1.gac.edu> youn...@gacvx1.gac.edu writes:
>> limited/no animation ... good graphics and 80 column text below...
> Yup, you can switch between 640 and 320 mode on each line... I don't
>think it's ever been done in anything...

This HAS been done, quite a while ago infact. Remember FillMaze?
The maze uses 320 mode, fill mode, and differing. The text at the
bottom uses straight 640 mode, giving 80 column text.

On the topic of FillMaze, it's a good way of testing out the Zip Chip.
You never get below 60 frames per second, sometimes, it gives you more.
(because it can redraw the screen twice before the scan beam displays it.
With background Sound playing away, I still get 60 frames per second with
most songs! And never below 59 with any song! Now if I can just get a
reliable Zip Chip GSX...
--
____
Y_,_|[]| Eric Mulholland
{|_|_|__| er...@sage.cc.purdue.edu
//oo--OO ...!pur-ee!sage.cc!ericm

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David H. Huang

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Jan 18, 1991, 10:37:39 AM1/18/91
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|Ok, I posted a message on this subject earlier with sort of a "rediculous"
|subject line, and nobody replied... so I'll try it again...
|
|Does anyone know if it is possible to:
|
|1. Achieve a 32 color grey scale by "bleeding" together the current 16 color
| grey scale. i.e. You display the following the first time the computer
| refreshes the screen:
|
| black black grey1 grey1 grey2 grey2 ... grey14 grey14 white white
|
| and then change the scan line to:
|
| black grey1 grey1 grey2 grey2 grey3 ... grey13 grey14 grey14 white
|
| thus creating the illusion of 32 shades of grey to the naked eye??
|
| I think I read about this being illustrated in some demo somewhere, but I
| have yet to see it. I mean, even if the overhead is very high on the CPU,
| and there is a slight flicker, it would be nice for displaying GIFs that
| utilize a high number of colors in B/W.

I'm sure this is possible, since there is a demo called Kompressor (or
something like that) which switches (normal) hires pages back and forth very
rapidly, so it seems to blend the two hires pages together. If you mix
a green screen (color 1) and a violet screen (2), you get this grayish
screen. It does flicker slightly, but it isn't too bad. BTW, the demo
runs on a ][+ or higher.

|2. If the above is possible, then it should also follow that one could change
| between 2 different sets of 16 colors on a line and change a few pixels in
| that line to achieve the illusion of 32 colors/line...
|
| right?

I would think so...

|3. If the gs can display 640x200x"800" and 320x200x"3200", then it should also
| be able to split 3/4 of the screen into 320x200x"3200" and the bottom 1/4
| into 640x200x"800", right? This would be great for an adventure game, with


| limited/no animation ... good graphics and 80 column text below...

Not quite... 640x200x"800" is 640x200x4 per scan line. If you use the whole
screen, you have 200 scanlines, so you get 640x200x800. If you're only using
the bottom 1/4 of the screen, you have 50 scanlines, which is 200 colors
on that part of the screen. Same applies to the top 3/4... 2400 colors.
But if you only want 80 column text below, you could just let the top
be 320x200x2400 and the bottom be 640x200x4.

|Ben
|
|youn...@gacvx1.gac.edu


--
David Huang |
Internet: ifa...@ccwf.cc.utexas.edu | "My ganglion is stuck in
UUCP: ...!ut-emx!ccwf.cc.utexas.edu!ifar355 | a piece of chewing gum!"
America Online: DrWho29 |

The Unknown User

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Jan 18, 1991, 4:43:05 AM1/18/91
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In article <1991Jan18...@gacvx1.gac.edu> youn...@gacvx1.gac.edu writes:
>Ok, I posted a message on this subject earlier with sort of a "rediculous"
ridiculous. I'm a card carrying member of the Spelling and Grammar
Nazis of America.

>1. Achieve a 32 color grey scale by "bleeding" together the current 16 color
> grey scale. i.e. You display the following the first time the computer
> refreshes the screen:
> black black grey1 grey1 grey2 grey2 ... grey14 grey14 white white
> and then change the scan line to:
> black grey1 grey1 grey2 grey2 grey3 ... grey13 grey14 grey14 white
> thus creating the illusion of 32 shades of grey to the naked eye??

That isn't creating the illusion of 32 shades of gray...

It's creating the illusion of more than 4096 possible colors...
That is, if your theory is correct, and you display gray1 the first time,
then gray1 the next time, your eyes 'see' gray1.5, which doesn't exist.
In my very quick thinking of this, I don't see much use, as if
you are differing by many colors, the 'average' of the two will probably
be very close to another color that already exists.
Like.. Gray3 then gray13 theoretically equals gray8, which already
exists.

>2. If the above is possible, then it should also follow that one could change
> between 2 different sets of 16 colors on a line and change a few pixels in
> that line to achieve the illusion of 32 colors/line...

The above explanation goes for colors too, but I would guess
even more so.. (i.e., the 'average' of two colors is more likely to be
veryveryvery close to a color that already exists)

>3. If the gs can display 640x200x"800" and 320x200x"3200", then it should also
> be able to split 3/4 of the screen into 320x200x"3200" and the bottom 1/4
> into 640x200x"800", right? This would be great for an adventure game, with
> limited/no animation ... good graphics and 80 column text below...

Yup, you can switch between 640 and 320 mode on each line... I don't


think it's ever been done in anything...

--
/Apple II(GS) Forever! unk...@ucscb.ucsc.edu MAIL ME FOR INFO ABOUT CHEAP CDs\
\WRITE TO ORIGIN ABOUT ULTIMA VI //e and IIGS! Mail me for addresses, & info. /

Todd P. Whitesel

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Jan 18, 1991, 5:24:32 PM1/18/91
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The gray scale trick has been done, I believe in an ACS demo disk that was
out last summer (if not before). They called it 'IIgs HAM mode' which is not
accurate.

Well, we will eventually be able to add something like this to LHG as an
option. However, I'm a bit skeptical as to how practical it will turn out
to be...

Todd Whitesel
toddpw @ tybalt.caltech.edu

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