Atari 8Bit Colour Pallette

[PeterJ]

There was a recent post from a user who had converted one of the games from [mention]R-Tape[/mention] to the Atari.

This made me interested to take a look at a few games from the machines. I remember the Atari having a reputation for excellence in graphics and colour with it's Antic chip. However I have to admit disappointment with many screens I looked at being monotone with a prevalence for what seems to be a golden brown. For example Feud.

Am I just looking at the wrong screens, or was there a reason for this? Thanks

[toot_toot]

The Atari 8-bit computers (and even the 5200 console) had games with really vibrant colours, this might just be down to a fast and dirty conversion, like most of the Spectrum to MSX conversions that didn’t make much use of the MSX’s capabilities.

Rescue on Fractalus, Star Raiders II, The Eidolon, Bruce Lee are just some examples off the top of my head where the colours were quite vibrant and with better graphics than the Spectrum versions. I’d imagine if you were looking at Spectrum conversions to the Atari, they probably didn’t have much money spent on them as the Atari 800 like of computers were never as big in the UK. Some exceptions would be Jeff Minter and Archer Maclean’s games that were developed for the Atari 800. But games developed in the US, where the Atari 800 was really big, tend to look much better.

[AndyC]

I believe it was a limitation of the display hardware. You could get extra colours on the screen but only different hues of the main colour. It probably made the machine look better in marketing blurb which featured "X colours on screen" type details, but from a practical perspective didn't really make for particularly colourful graphics.

[Pobulous]

I think part of the issue is that the original graphics hardware is more limited than the XL/XE range, so many games didn't fully utilise the newer GTIA modes, which would allow more colours. Bosconian, a modern release, is nice and colourful.

I believe in the original CTIA the choices were 4 colours, or 1 hue with 16 shades, or 16 hues with one shade. So the 16 colour modes would be either garish or 16 shade monochomatic.

You could also change display modes and colour palettes every line without much effort, so there's not much excuse for that screen. I guess after the C64 took off, a lot of games would have been quick and dirty ports from that.

[Ralf]

Atari 8Bit is a very unique machine.

Believe it or not but even today there are new graphic modes discovered for it

Yes, it doesn't have one or three or any fixed number of graphic modes. As I understand you define your graphic mode by writing some configuration in memory. Many of these configurations won't work at all but sometimes you may discover something surprising.

As a curiosity, some guys discovered that Atari graphic modes depend on... computer temperature If it works long enough and is warm enough then some effects are possible which won't work directly after turning you machine on. Some analogue effects, changed resistances of hot parts etc., I believe.

I've actually been to a retro party where a guy was warming Atari with a...hairdryer taken from his wife to avoid waiting and show new graphic modes.

So going back to original topic, you don't have strong, vibrant colours on Atari for free, like on Zx Spectrum.

If you are beginner/average programmer you will probably end with shades of grey/brown.

If you are good, you may have something like:

[Pegaz]

We shouldn't forget the best hires version and programmers masterpiece.

[Joefish]

This is the CTIA 128-colour palette. Without any further hacks you either get to use one row or one column of this palette at a time.



So graphics either tend to look a bit dark or misty as they use colours with the same luminance, or monochrome / sepia as they use one colour in 8 shades. Note that when you pick one multicoloured row you don't have both black and white in the palette!

The only way round that is to use a four-colour mode, where you can assign any four colours from the palette.

But since it's an Atari, you can assign a list of changes to switch palettes and modes on different screen rows. And it has a limited number of sprites, which can be re-used as you go down the screen.

[Ralf]

This is the CTIA 128-colour palette. Without any further hacks you either get to use one row or one column of this palette at a time.

I believe it's more complicated, they have also sprites and in many games sprite feels to have very different colours from the rest

They also seem very often to use just 4 colours for the background while according to this picture they could 16 colours for free:

[akeley]

I agree with [mention]toot_toot[/mention], its' more about the devs than machine's limitations. For whatever reason, some just took the easy route. Apart from aforementioned games you can look at the likes of Ninja, Bounty Bob, World Karate Championship or Pathfinder (and I'm sure many others) for great use of colour. I think it can be on par - or better - than C64.

[Lethargeek]

No, it IS about the machine limitations as well. In short, Atari 8bit has excellent "vertical", but very limited "horizontal" color capabilities.

In detail, the Atari has background and sprites. There are no set screen modes for the entire background, as it is actually a customized stack of separate "mode lines". IIRC the each mode line can be a single pixel scanline, a double-height pixel scanline or a text mode line consisting of several scanlines. Modes and palettes for the each line are independent. A pixel line can be high or low resolution, but (beside PAl/NTSC artifacts) you get only 4 independent colors per line for low-res and only 2 non-independent (same hue, different brightness) for square-pixel hi-res. Compare it with maximum of all 15 Spectrum colors per line. Even if these 4 colors are selectable out of 128 colors palette.

Sprites might add some more colors per line, but you need them for, well, sprites)) and they are of limited width, even if scaled, and even more limited in colors - only one color per sprite scanline, and to select another for the next scanline you need to set raster interrupts.

As you see, this arrangement is not well suited for top-down or top-side-down view games like Feud. It's much easier to select the same 4 colors for the entire playfield in this case, especially if the background objects layout in the area comes from a different machine original version. OTOH it allows nice gradients in 1st-person racing/flying and side-view games.