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Atari 8-Bit Graphics Capabilities


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On 7/18/2019 at 6:36 AM, José Pereira said:

(just can't see how and already contacted Albert here because I don't get how to edit these bottom information on this new AtariAge forums but sadly and from a long long time I don't have his answer).

At the top drop down your username and pick Account Settings

2095708595_Screenshot2019-07-19at06_34_49.jpg.b3d97fb13c23082709f55f134a2338f0.jpg

 

Signature is about half way down

 

 

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5 minutes ago, José Pereira said:

It seems that usual PAL Blending technic (that wouldn't look good on NTSC machines) where on intercalated scanlines you have:

-> red, green, yellow;

-> black, gray, white;

(And blue is BAK register so is possible on all scanlines but it can also blend with all those above)

Yeah, but I just checked the image, zoomed in, and the interlaced lines are empty, there's no shade, nothing to blend with. It's just black.

 

I presume there's DLIs (to change per-scanline color registers), that's the de facto standard, easiest way to get multiple colors on Atari.

 

But the hues confuse me. Where do those come from if not from blending ? Now, if you had GR.10 on those interlaced scanlines (via Display List), yeah - those would blend very nicely with the Antic F (containing the actual image data).

 

BTW, is the reason for the worse-quality NTSC color blending the fact that on PAL there's simply more time for colors to blend ? Or is it in the HW ?

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Now I also downloaded and zoomed the picture. Most of the intercalated scanlines seems to have only black but there are also some that have solid colour in consecutive scanlines line the front of the car.

If you zoom for a large large picture you'll see that the intercalated scanlines aren't really black.

It seems that the in-between scanlines aren't using the usual black, gray and white but also the blue, green, red and yellow that blending gives this nice result?

Where's this and who«s the artist?

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Damn, this is hands down the best concealed blending I have ever seen !

 

I was previously only zooming to 1000%, so I couldn't  see  perceive anything but the black inside the interlaced lines.

 

But now that I zoomed to 3000%, of course there's some pixels there!

 

Can somebody please post a photo of this from a CRT TV ? This must look absolutely stunning on a real TV.

 

Thanks Jose for making me zoom in again !

 

 

BTW, your Loading screen looks great. Such nice warm colors. It screams Atari from distance. It doesn't even have DLIs, right ? Just PMG underlays for letters ? What a simple concept, yet the effect is beautiful!

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21 hours ago, Gunstar said:

It's just a loading screen, I wouldn't care if there wasn't a loading screen, it's the game that is important to me.

Did you never get excited as a kid about a beautiful loading screen ?

 

To this day, I still recall collecting my jaw from the floor, when Lucasfilm logo popped up on my Atari when loading Fractalus. That was more than 3 decades ago.

 

 

For me personally, both the Loading screen and Main screen are an intrinsic part of the Atari's charm :)

 

No 3DFX or nVidia GTX:1024 ever came close :lol:

 

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1 hour ago, VladR said:

You can also mix 4 hues and 4 brightness levels in 4 color mode. If you add character mode and PMG, you get 6 brightness levels. And using 2 frame flickering you can get 8 hues and 11 brightness levels. That can make images like this:

 

lambo.8x11F.png.ef104159aa0d2dd6527f86c2e13f65de.png

Humm... Why didn't I read it all/well. He says it all there (and were R0ger who did it?).

So it has flicker and to have this result you must be in PAL that flickers too much vs NTSC.

It maybe not so good ;)...

Edited by José Pereira
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1 hour ago, VladR said:

BTW, is the reason for the worse-quality NTSC color blending the fact that on PAL there's simply more time for colors to blend ? Or is it in the HW ?

No. It is in the TV color format. NTSC uses 422 subsampling, which means that every row, but only every other column gets an independent color - or to put it differently, the chroma (hue) information is subsampled horizontally, but not vertically.

PAL, however, uses 420 subsampling. This means that the chroma information has half the resolution horizontally *and* vertically, so any PAL TV *has* to bleed colors from two neighbouring lines. The reason why PAL uses also vertical subsampling is to avoid typical NTSC chroma defects (like faces turning green) due to phase shifts in the signal. While NTSC required a "tint" knob, PAL did not suffer from this because any phase shift between alternating lines would cancel out. So colors on a PAL TV tend to bleed out and loose intensity, while on NTSC, they would just get wrong.

The price to pay is the reduced vertical resolution, and the price to win is that you can mix colors. Note that this only works for the hue. The luminance does not mix.

 

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1 hour ago, VladR said:

 

Did you never get excited as a kid about a beautiful loading screen ?

 

To this day, I still recall collecting my jaw from the floor, when Lucasfilm logo popped up on my Atari when loading Fractalus. That was more than 3 decades ago.

 

 

For me personally, both the Loading screen and Main screen are an intrinsic part of the Atari's charm :)

 

No 3DFX or nVidia GTX:1024 ever came close :lol:

 

Of course, and it is always better to have great opening screens, I am simply saying that you can have great opening screens and if the game isn't good, who care's? Are you going to load up the game frequently just to see some splash screen's? And even the best get old after a while. I love the Lucasfilm loading screens, but they are also animated, not just stills, and you can't avoid them if you wanted because the game is loading while it is displayed. I'm referring to screens with no animation that you can skip, so after seeing them, I'd rather get to the game than waste time looking at them.

 

One of my all-time favorite's are the Alternate reality opening "movies" but after seeing them a few times, they get boring, no matter how good they are and so I skip past because I can. The game itself is what is important, otherwise go watch demos and look at static graphic art screens. Aren't you loading the game to play? Or just to see opening/loading screens and then shut it off when the game is loaded? YES, I would rather have a good game without loading screens than a bad or mediocre game with great loading screens. I stand by what I said, I guess I just had to spell it out for you and be captain obvious rather than you infer what I meant.

Edited by Gunstar
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Matter of fact, yes - I used to load up some games just for splash screens and main screen, as the game itself was boring :lol:

 

Then again, as a coder myself, I'm partial to the demoscene, so there's an obvious bias towards enjoyment of non-interactive content :)

 

Of course, from a pure gamer standpoint, yeah - the cutscenes go through the following stages:

 

1. Wow, that's so cool.

2. Alright, alright, alright - I saw that already

3. WTF ?!? No Escaping this BS ?

4. AAAAAAAAAARGH   #$!&& !!!!

 

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49 minutes ago, VladR said:

Ouch :)

Anyway, it's still an amazing piece of work.

 

Would have to see the real thing, though. Video can't really reproduce the flicker that you see in real life...

 

Yep, it's flicker-hell on PAL and hurts your eyes within a few seconds. Not useful within any game or program, not even useful as a "still" picture since it does not stand still (flickers extremely badly). Whoever said Crownland has flicker should look at this picture on PAL for several seconds - now everything, including the real world, has flicker... ;-)

 

Besides, this picture as well as most Rasta pictures do not look as good on the real A8 as they do in the screenshots here. Why ? On the A8 it is (they are) fullscreen, so you can see every single pixel, if you are sitting in front of the screen (e.g. only 30-50 cm away). You have to stay away some 2-3 meters from the screen to see and recognize the whole picture. [Set the emulator window to fullscreen to see what I mean...]

 

 

Edited by CharlieChaplin
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9 minutes ago, VladR said:

Matter of fact, yes - I used to load up some games just for splash screens and main screen, as the game itself was boring :lol:

 

Then again, as a coder myself, I'm partial to the demoscene, so there's an obvious bias towards enjoyment of non-interactive content :)

 

Of course, from a pure gamer standpoint, yeah - the cutscenes go through the following stages:

 

1. Wow, that's so cool.

2. Alright, alright, alright - I saw that already

3. WTF ?!? No Escaping this BS ?

4. AAAAAAAAAARGH   #$!&& !!!!

 

I am an artist and do like static screens and demos too and for that reason am also partial to the demo scene and static screens. Otherwise why would I bother spending the hundreds and hundreds of hours doing Rastaconverter images and taking the time to get as good at it as I am and bother re-attempting images on average a dozen times, sometimes dozens  of times! But even some of the best out there, after watching a half-dozen times gets old and I don't load them up anymore for years, then maybe go back and look again, once or twice, they get boring again quicker and then I don't bother anymore at all. By the time I get a Rasta image good enough to me to post, I'm sick of it and don't look at them again for months or years and only then to see how I am improving over time. The first 50% of the images I posted I feel like they suck now and may redo them all some day!

 

The first time I upgraded to 512K and could finally watch the 320K Numen on a real machine, I watched it over and over. Now it's been 10 years since I loaded it.

 

And yes, I agree with your 1-4 points 100%, that's what I meant in the first place, in the end the game is what is important.

Edited by Gunstar
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I never saw Rasta's output on real TV, so can't really judge it, but I believe Gunstar does that often and if I recall correctly, he always says that output on real TV is much better than what we see here in the thread, so I'll take his word for it.

 

But 3 meters distance to enjoy the picture ? Damn, that would be brutal :)

 

 

You just reminded me of some flickering demos I saw as a kid, and since I grew up in PAL land, I still recall how badly sensitive I was to the flicker at that time. I'm not the guy to complain of headaches, but man - that stuff was painful after 2 minutes :lol:

I'm absolutely sure I couldn't handle it today. God Bless LCD :)

 

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19 minutes ago, CharlieChaplin said:

 

Yep, it's flicker-hell on PAL and hurts your eyes within a few seconds. Not useful within any game or program, not even useful as a "still" picture since it does not stand still (flickers extremely badly). Whoever said Crownland has flicker should look at this picture on PAL for several seconds - now everything, including the real world, has flicker... ;-)

 

Besides, this picture as well as most Rasta pictures do not look as good on the real A8 as they do in the screenshots here. Why ? On the A8 it is (they are) fullscreen, so you can see every single pixel, if you are sitting in front of the screen (e.g. only 30-50 cm away). You have to stay away some 2-3 meters from the screen to see and recognize the whole picture.

 

Back then there was a small computer store nearby that me and my neighbours spent there hours playing games because the owner and the employer were nice guys.

They had an Amiga and a C64 all with Commodore monitors. Here the C64 appeared too late and was never a big seller so all my friends were allmost all ZX/Timex owners (the Timex computer factory was here so there was many 2048 and 2068 with that cart emulating ZXs) and they were always saying bad things about the C64 games and it's block 2:1 ratio pixels while they had small and detailed stuff.

Why? Just because on the monitor (I think it was a 1702) you see exactly the square pixels and no blend/artifacting, nothing... and they also had only TVs at home so the images blur but also all the C64s games I remember seeing there were multicolour 2:1 ratio ones, even the sprites (back then I even didn't know that C64 could have the two modes mixed and hi-res sprites untill I start to see some magazines on the shops).

I remember that, as an A8 owner habituated to 2:1 and multicolour, was the only defending the poor and humble C64 ?.

When some of them were in my home playing A8 games (and ours pixels/screen size vs C64 same 320x are even bigger) they never say nothing and notice the square pixels because I had a TV and was the PAL Blending ? though they still 'attack me' for not having all those arcade, driving and movies big names games they had for them ?.

 

Edited by José Pereira
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31 minutes ago, VladR said:

I never saw Rasta's output on real TV, so can't really judge it, but I believe Gunstar does that often and if I recall correctly, he always says that output on real TV is much better than what we see here in the thread, so I'll take his word for it.

 

But 3 meters distance to enjoy the picture ? Damn, that would be brutal :)

 

 

You just reminded me of some flickering demos I saw as a kid, and since I grew up in PAL land, I still recall how badly sensitive I was to the flicker at that time. I'm not the guy to complain of headaches, but man - that stuff was painful after 2 minutes :lol:

I'm absolutely sure I couldn't handle it today. God Bless LCD :)

 

Yes, to me Rasta images look much better on a real TV because you see the true colors of the Atari that you DO NOT see in the posted images, plus I have upgraded video on my real machine which has much richer color than posted .png images. But I also don't mind seeing all the pixels at full screen size rather than a thumbnail @CharlieChaplin says, if I did, I wouldn't bother with an Atari 8-bit and it's graphics at all. Especially when in most cases the graphics have much less color plus are "blocky." I stand 100% behind my comment that they look much better on a real TV/monitor, if charlie thinks they don't just because he can see the pixels, maybe he should try stepping back until they are the size of the .png images posted in the thread!

 

But I have no trouble enjoying the amazing images Rastconverter produces up-close and personal as I see with ANY graphics on the A8 or other 8-bit machines. You either except them for what they are, 4 colors or 128/256, or why bother with these old low-res machines at all? I don't see how someone can enjoy any graphics, demos or games on old 8-bits if they think Rasta Images look bad on the real hardware, or even full-screen on an emulator (unless emulator users reduce the window size to actual 4x3 inches for 4:3 ratio!) I recall when people have suggested how cool graphic text adventures would look with Rasta images and others say it would look terrible because of the low resolution, but then wouldn't they still be far, far superior to the old graphic text adventures with a mere 4 colors?!? Those people just need to move on too modern computers and shut up and let the rest of us enjoy are low-resolution old-school graphics.

 

Rasta images look much better on a real Atari close-up than they do on an emulator at full-screen close up and they look much better if you stand back so they are the same perceived size as the small .png images in the thread. Period. Do the real full-screen Atari Rasta images, except for color, look better in the small .png thread images? Not unless you step back, true, but the color on the .png images is far worse not matter what.

Edited by Gunstar
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2 minutes ago, Gunstar said:

And yes, I agree with your 1-4 points 100%, that's what I meant in the first place, in the end the game is what is important.

 

Hehe, that's why I ask sometimes to have no more than one title or loading picture in front of a game. If loading (playing) the game several times it gets boring (annoying) to load several intro/title/loading pictures again and again. Evil as I am, I changed Bomber, Mighty Jill and a few other games (think Bosconian also) in my personal collection to have only one loading or title screen and removed all others (e.g. removed all lesbian screens from final version of Mighty Jill)...

 

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4 minutes ago, CharlieChaplin said:

 

Hehe, that's why I ask sometimes to have no more than one title or loading picture in front of a game. If loading (playing) the game several times it gets boring (annoying) to load several intro/title/loading pictures again and again. Evil as I am, I changed Bomber, Mighty Jill and a few other games (think Bosconian also) in my personal collection to have only one loading or title screen and removed all others (e.g. removed all lesbian screens from final version of Mighty Jill)...

 

?

On Bomber? And do you ever thought of all the hours, days and nights, weeks I lost to do all them?

?

?

:thumbsdown:

 

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12 minutes ago, CharlieChaplin said:

 

If loading (playing) the game several times it gets boring (annoying) to load several intro/title/loading pictures again and again. Evil as I am, I changed Bomber, Mighty Jill and a few other games (think Bosconian also) in my personal collection to have only one loading or title screen and removed all others (e.g. removed all lesbian screens from final version of Mighty Jill)...

 

Wait, you mean you disassembled the game executable and hacked it in hexa editor to remove the calls to those functions ?

 

I now stand corrected and understand I should have added Stage 5 to my Cutscene Enjoyment Phases:

IDareYouMF02b.thumb.gif.4761619420c418afb9e2bd45f9b97fe5.gif

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8 minutes ago, VladR said:

Wait, you mean you disassembled the game executable and hacked it in hexa editor to remove the calls to those functions ?

 

I now stand corrected and understand I should have added Stage 5 to my Cutscene Enjoyment Phases:

IDareYouMF02b.thumb.gif.4761619420c418afb9e2bd45f9b97fe5.gif

Even I enjoy them the first few times, until they get old too me. But would I still want the games without them? Of course, but as an artist I DO appreciate them until they get old, which includes my own art work. I understand Jose' frustration with the long time and hard work he puts into them, as I do with Rasta images, but I do get sick of my own Rasta images after staring at them for hours and hours, day after day while trying to improve them. But I go back much later and enjoy them again even if some of my older ones I think I could improve a lot, after all my years and thousands and thousands of hours experience with Rasta.

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17 minutes ago, José Pereira said:

?

On Bomber? And do you ever thought of all the hours, days and nights, weeks I lost to do all them?

?

?

:thumbsdown:

 

My personal collection, my personal choice... ;-)   (Kept the Bomber title screen, removed the other screens; after the title, the game loads.) But don't worry, I don't have an A8 webpage for downloads, so the "shortened" programs do remain in my personal collection only. Back in the 80s this was done more often, to save space and loading time, especially for tape users. And I have been a tape-only user until 1992 or 1993, when I bought my first A8 disk drive... so I am used to having games without any title picture or just one title picture...

 

11 minutes ago, VladR said:

Wait, you mean you disassembled the game executable and hacked it in hexa editor to remove the calls to those functions ?

 

Much easier, I am no programmer so I did not disassemble anything. Just loaded the XEX into a packer / linker and removed some data segments (and init adresses) and tested the end result again and again, until it worked like I wanted...  ;-)  And when I could not get it working, I asked some Atari friends to do it for me...

 

 

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Back to topic. Maybe someone can post some nice screens that a) show all available standard A8 gfx. modes (one pic/screen each for Gr. 0 to Gr. 15) and b) several screens with new/modern gfx. modes like HIP, RIP, TIP, CIN, MAX and many others...?!?

 

For the standard modes it would be nice to have some game or demo screens (e.g. "this example shows a Gr. 0 screen:", "this example shows a Gr. 1 screen:", etc.), for the modern gfx maybe one could use some picture or demo screens... ?!?

 

 

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3 hours ago, VladR said:

How exactly is this one done ? At first I thought that since this is interlace, then we're talking PAL blending, and alternating two different framebuffers. It's also not using PMGs, as you say that would give you 6 levels.

 

But then you mentioned the 2-frame flickering would give you more, so it implies that the image above isn't using flickering.

 

I would understand additional colors would be produced/artifacted if it wasn't interlaced with blank lines (as at that point, any color below the current scanline will "bleed" some color into the color above it). But the interlace makes it confusing for me to guess what exactly is going on here. Is this a carefully timed kernel ? But then you wouldn't talk about hues, it would be straight new colors. So, why hues exactly ? Is the every odd empty scanline a GTIA mode ? It's still empty, so it shouldn't matter to color blending, no ?

Let's take it in steps. It's something I worked for months, and the final stage is quite complex unfortunately.

 

First step is 4 hues, 4 brightness values. Odd lines are hues, even lines are values. PAL mixing gives me 16 colors.

My first approach was red, green, blue, black for hues. But then I realized I don't need black (which would give me various grays). Gray is not very common color, and can be easily dithered using the other colors. So instead black I use yellow, as the yellow i get by dithering red and green is quite bland.

You can also use other hues if the picture misses one color. Like that Pong demo .. it doesn't have green, so the palette uses yellow, red, blue and orange IIRC.

This basic mode does not use char mode (but it can), and does not use PMG. Also it does not flicker, and has the usual memory size. There is kernel routine, which changes 4 color registers every line, so it's pretty CPU intensive. It's the simplest mode though.

 

The Lambo picture in this mode looks like this (xex bellow). I call this mode RGBY.4x4.

 

lambo_4x4.png.8893577f71f94b226d031cdf91e779f7.png

 

Now .. 4 hues is OK. 4 values is not. That's what makes the picture look rough. Using PMG and char mode we can get 6. 4 in every individual character, of course. You can look at it as every character is either dark, average, or bright. If we had levels 1,2,3,4,5,6 .. the average chars will use 2,3,4,5. Bright char will swap 2 for 6. And dark will swap 5 to 1. Hues are the same in all characters, I tried to somehow swap them too, but it's not really needed.

This mode obviously only works in char mode, and it consumes all PMG (stretched to max size). It needs extra memory for the PMG and character map. The kernel is pretty much the same, I don't have to change any extra color. Badlines complicate it hugely though. In this mode the kernel has to be unrolled, the loop cannot be fitted into it. Maybe it could be done on normal lines, there is always room for improvement.

Btw. the Pong demo uses character mode and 5 brightness values, as the PMG is used for the ball. So it's something between 4x4 and 4x6. Character mode, amount of changes needed per line, and scrolling, make the kernel code nightmare level complex.

 

Lambo in this mode looks like this. I call this mode RGBY.4x6

 

lambo_4x6.png.9f8d8c709c45d280b85593455b4e479c.png

 

Another step is the interlacing. There isn't really interlace in Amiga sense, the hue and values lines do not swap. I don't want to increase resolution. The previous modes give reasonable 160x100, square pixels. Ideal.

I want to increase color and brightness depth. Lately I call these mode flicker modes instead if interlaced. By flickering red and blue, I get extra purple hue. By flicker 2 neighbor brightness levels, I get something in between, and so on.

This approach doubles amount of hues, it gives me one more between each neighbors on hue circle. And I get twice as much minus one brightness values. I only flicker neighbor values, to improve perceived flickering. So instead of 4 values I have 7, and instead of 6 I have 11.

If you use this flickering approach for brightness values, there is one problem. One of the field (one of the two pictures you flicker) covers even values from the source image, and the other covers odd values. One of the two is on average 1 step brighter. That makes the picture flicker quite visibly. But it can be drastically improved by exchanging pixels between field in checkerboard pattern. This then can collide with dithering used in the picture itself, but since I used Floyd-Steinberg, specially modified to break any repeated patterns, it's no problem.

 

The kernel and working of the individual frames is the same as with non flickered variants. The palettes are the same too. It all takes twice as much memory.

All the smart stuff is done during the conversion.

 

Here is the Lambo in flickered 4x4, which I call RGBY.8x7F.

 

lambo_8x7F.png.fa50a64f239c137abe2d75b14e9721d9.png

 

And here is flickered 4x6, which I call RGBY.8x11F.

 

lambo.8x11F.png.59be8d636151bf321e06734813c1e8c2.png

 

Recently I made some more small improvements, but it's nothing drastic. I can make better gray in flickering mode, and I improved character boundaries artifacts in character modes. But let's not deep too dive into this now. Also I had these pictures prepared for my talk about the mode on Atariada 2019.

 

And here are the XEXes. In emulation you need PAL artifacting, and the same refresh rate as your screen. Or frame blending. 50Hz emulation on 60Hz screen will create unrealistic 10Hz flickering, it's not supposed to look like that !

On real hardware, keep in mind that it wont flicker at all on modern LCDs. It should look decent on CRT TVs. The flickering is somewhat more visible on CRT monitors.

 

lambo.4x4.xexlambo.4x6.xexlambo.8x7F.xexlambo.8x11F.xex

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