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MoonTurtle

Atari ST 16-color limitations and tricks

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I was wondering about any limitations that the standard color graphics mode of the Atari ST (other than only having 16 colors to work with.) and how developers tried to work around these limitations,

 

Now sometimes it's hard to discuss this kind of topic without using some examples, but this can be a bit tricky to so for Atari ST because, when it comes to color graphics on the ST, there are two main ones, there's the standard 16 colors out of 512, and then there's the STE, which I'm told (I could be wrong) is 32 out on 4092 colors, the ladder being most common in late Atari ST games, mostly in the 90s.

 

Which is why it's tricky to bring up an example here, I was going to use Wolfchild on the ST as an example of some way to work around the 16 color limitations. but I have a feeling that's an STE game, not an ST game, because looking at the graphics, the game uses way more than 16 colors,

 

But I did have an idea, maybe the background graphics and foreground graphics use their own respective palettes, but I don't know if that's truly the case or not.

 

This topic is for the graphics side of Atari ST development. so people who are developing for the ST/STE/STF can learn tricks/loopholes/exploits and just general knowledge of graphics on the Atari ST.

 

This is mainly for the standard 16-color graphics mode of the ST, but the enhanced graphics of the STE and STF(Falcon) can be discussed here as well.

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the STE also only had 16 but out of a palette of 4096 colors

 

but you could do some trick, to get more on the screen.

 

edit add some info.

 

The St and STE had a 32000k Screen array.

and it had 4 bit planes in low res

2 bit planes in medium res

and 1 bit plane in high res

 

giving it 320x200 and 16 colors in low res from a palette 512 (ST) and 4096(STE)

in medium res it had 640x200 4 colors

and i high res 640x400 Black and white

 

the formula in low res is

(320 / 16 pixel) * 4 (bit plane) * (2 for word for the 16 pixel)

it have a interleave for the graphic,

 

so first one word (16pixel) for bit plane

so a word for bit plane 2

so a word for bit plane 3

so a word for bit plane 4

 

then word for bit plane 1

ect.

Edited by fedepede04

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Yes, STE has still only 16 colors at once on screen, only that palette is 'finer' - that is visible in case of some gradation effect, like sky - on STE if will be with less rough transitions.

 

However, programmers found way to display much more colors at once - first was Spectrum 512. The thing is on changing palette 'on fly' . Later came more advanced solutions, for STE, so we can have almost photo quality, even in movie playback:

http://atari.8bitchip.info/movpst.php

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I was wondering about any limitations that the standard color graphics mode of the Atari ST (other than only having 16 colors to work with.) and how developers tried to work around these limitations,

 

Now sometimes it's hard to discuss this kind of topic without using some examples, but this can be a bit tricky to so for Atari ST because, when it comes to color graphics on the ST, there are two main ones, there's the standard 16 colors out of 512, and then there's the STE, which I'm told (I could be wrong) is 32 out on 4092 colors, the ladder being most common in late Atari ST games, mostly in the 90s.

 

Which is why it's tricky to bring up an example here, I was going to use Wolfchild on the ST as an example of some way to work around the 16 color limitations. but I have a feeling that's an STE game, not an ST game, because looking at the graphics, the game uses way more than 16 colors,

 

But I did have an idea, maybe the background graphics and foreground graphics use their own respective palettes, but I don't know if that's truly the case or not.

 

This topic is for the graphics side of Atari ST development. so people who are developing for the ST/STE/STF can learn tricks/loopholes/exploits and just general knowledge of graphics on the Atari ST.

 

This is mainly for the standard 16-color graphics mode of the ST, but the enhanced graphics of the STE and STF(Falcon) can be discussed here as well.

 

CPU Interrupts are often used to swap out the color palette part way through drawing a screen. The easiest way to do this is at the start of a line, so that each line in effect gets its own unique palette. Programs like Spectrum 512 changed it mid-line so it would have 48 unique colors per-line. I believe mid-line color palette changes are more CPU intensive than interrupts at the start of a line.

 

In case you aren't familiar with the term, an "interrupt" in computing terms is just like someone at work interrupting you to work on another task. they can be scheduled or trigger by external events (mouse moves cause interrupts that get the computer to update the pointer). For increasing colors you would tell the computer "excuse me, but if you could change the palette to this before drawing line 96, that would be super!" (and saying please is accurate because some interrupts are allowed to be ignored under load). These interrupts also happen independent of the main program after you set them up, so that's nice from a coding aspect.

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There is a technique to create the ilusion (for our eyes, the result is far more colours at once) of more colours; using a single 16 colour palette.

 

Its called dualfield dithering; you create colour pairs and colour mixtures due to pixel positioning, in order to create shades of base colours (the 16 colour palettes)

 

See Atari Game Tools videos or these ones:

 

https://www.youtube.com/watch?v=FMrdjrrtxWo

 

https://www.youtube.com/watch?v=D1oAdc6MjQM

Edited by masteries

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On 4/4/2019 at 6:51 AM, MoonTurtle said:

I was wondering about any limitations that the standard color graphics mode of the Atari ST (other than only having 16 colors to work with.) and how developers tried to work around these limitations,

 

 

there are some great tools for preparing/converting 16 or more colors graphics for ST like:

16color:
http://atari.anides.de/


Multicolor:
http://tool.anides.de/

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1 hour ago, mchorvat said:

this is cool! but is there a way to upload own image? i can't see any upload button/file selector.

yep, just drag and drop your image

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On 4/5/2019 at 7:45 AM, ParanoidLittleMan said:

Yes, STE has still only 16 colors at once on screen, only that palette is 'finer' - that is visible in case of some gradation effect, like sky - on STE if will be with less rough transitions.

 

However, programmers found way to display much more colors at once - first was Spectrum 512. The thing is on changing palette 'on fly' . Later came more advanced solutions, for STE, so we can have almost photo quality, even in movie playback:

http://atari.8bitchip.info/movpst.php

When looking at those movie clips, hard to believe it's an STe.  I suppose our biggest limitation back then was not color palette or resolution, but lack of storage space!

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10 hours ago, zzip said:

When looking at those movie clips, hard to believe it's an STe.  I suppose our biggest limitation back then was not color palette or resolution, but lack of storage space!

Yeah, lack of storage space, but also slow hard disks for such task. + lack of digital video sources.

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