Atari 8-Bit Graphics Capabilities

[PixelCrunch]

7 hours ago, Gunstar said:

With modern LCD displays. flickering in software modes is less noticeable, or can be completely eliminated on some TV's or if upscaling converters are used like I have. I can turn it on or off with my S-video-to-VGA converter/upscaler. The color is also more vibrant due to the video upgrade in my 1200XL.

What upgrades do you use? And what upscalers? This sounds really interesting.

[Gunstar]

What upgrade you want for your video, IMO, depends on the computer, but also keep in mind I have no experience with any newer upgrades you can buy and install, like the UAV, or Sopia board or even the VBXE which also provides RGB output which is going to be better than any S-video upgrade. But I do have both RGB/component and S-video/composite converter/upscalers to VGA, and one cheap Chinese one S-video-to-HDMI.

 

Though I am thoroughly impressed with the, SuperVideo 2.1 1200XL version, that I did on all my 1200XL's, if I were going to do it today, I'd probably get the UAV or Sophia boards for a video upgrade. I'd stay analog though and go with an RGB out that I can feed to my VGA converter.

 

But if you are a DIY type of person, then I say do the latest S-video Clearpic mod for any XL or XE except the 1200XL. Do the Super Video 2.1 for it, which makes use of the unique chroma boost circuit the 1200XL had that no other Atari has. But they botched it and ended up not connecting Chroma at all to the monitor port. It gets fixed with this mod, and is wonderful. 

 

My brand of choice for reasonably priced, quality converters and up-scalers is Ambery, especially for analog composite and component video to VGA. There are direct links below. The  two converters I use, the RGB Ambery AV-1 EV422 also known as 15Khz RGB CGA/Component YCbCr to VGA Converter Scaler for over a decade, the S-video Ambery AV-8R1 EV1387 also known as Ultra Composite Video S-Video To VGA Converter Scaler for a couple of years. 

http://www.ambery.com/vitoxgacoscs.html

 

http://www.ambery.com/rgbcovitovga.html

 

All my video and RGB sources go through switch boxes and then into one of these two converters then out to a VGA switch box and finally to VGA input on my LCD TV's and CRT VGA monitors. (currently, once I get my CBM 1084S-P CRT fixed then my PAL 1200XL will use it via chroma/luma)

 

 

Edited July 12, 2019 by Gunstar

[Irgendwer]

On 7/11/2019 at 4:44 PM, zzip said:

2) Alternate graphics modes in a display list.   One line may have gradient values while the other has color value.   Again it tricks your eye, but if you look closely it's easy to see how this was done.

On PAL TV systems this isn't related to "eye trickery", but (ab-)uses the way the system works with it's halved and averaged color resolution. The color on screen is a real solid mixture of the lightness and hue and not produced by human interpretation.

(The same is true for use of  "NTSC-artifacting".)

 

TV Input:

 

PAL output:

 

Source:

vincent-van-gogh-sternennacht-ca-1889.xex

[PixelCrunch]

Ok, so i’ve provided some sample images so you could discern the argument better.

 

NOTE: I used Retrospecs v.2.9 to generate these images. The palettes may be slightly off for you, but for me it’s pretty damn accurate.

 

GTIA NTSC, 80x192, 16 Colors.

GTIA NTSC, 80x192, 16 Colors per Scanline.

 

Which one is more accurate to the hardware of the 8-Bit series from Atari? (Any model) Let me know.

[+Philsan]

Standard graphics mode are displayed here:

http://gury.atari8.info/ref/graphics_modes.php

Atari has overscan, therefore modes are not limited to 320x192, they can be up to 336x240 pixels.

Thanks to display lists, graphics modes can be mixed together.

Thanks to display list interrupts, you can have tens of colors.

For example, this 160x212 pixels image has 101 unique colors:

(tune's stereo thanks to double Pokey audio chip).

Tons of colorful images are in this post and in the thread 

 

Mixing display modes, colors and sprites (overlapped sprites generate colors) you can have many combinations.

 

You see, it's not easy to make a list of Atari graphic modes...

 

 

In addition, as in other platforms, there are interlaced graphic modes.

 

[Gunstar]

DP.

Edited July 13, 2019 by Gunstar

[Gunstar]

35 minutes ago, PixelCrunch said:

Which one is more accurate to the hardware of the 8-Bit series from Atari? (Any model) Let me know.

Both. Either GTIA mode 11 with 16 colors total, or GTIA mode 11 with DLI's allowing 16 colors per scanline. Actually, just plain mode 11 with 16 colors can use them all every scanline, with DLI's many more colors per screen.

Edited July 13, 2019 by Gunstar

[PixelCrunch]

Just now, Gunstar said:

Both. Either GTIA mode 11 with 16 colors total, or GTIA mode 11 with DLI's allowing 16 colors per scanline.

But which one is used more?

 

Please give me solid and easy-to-understand advice! The 8-Bit Series is something i WANT to like, and i’m trying to like it really hard!

[Gunstar]

Why is it hard to like? what is making it difficult to like? That just sounds like double-talk to me. More graphic modes, more colors, more abilities, mix modes, change display lists for tons of colors on-screen at once. What's NOT to like?!? Take away sprites, and no other 8-bit computer can compare graphically with all the flexability and 128/256 color palette that was unheard of in 8-bits outside Atari computers.

 

Have you even taken the time to look at this thread, which is just one of many ways of using Atari graphics? https://atariage.com/forums/topic/200118-images-generated-by-rastaconverter/?tab=comments#comment-2556201

160x240 resolution, up to 128 colors on-screen, up to 15 colors per scan-line, from a palette of 128 colors,

 

Edited July 13, 2019 by Gunstar

[PixelCrunch]

Just now, Gunstar said:

Why is it hard to like? what is making it difficult to like? That just sounds like double-talk to me. More graphic modes, more colors, more abilities, mix modes, change display lists for tons of colors on-screen at once. What's NOT to like?!? Take away sprites, and no other 8-bit computer can compare graphically with all the flexability and 128/256 color palette that was unheard of in 8-bits outside Atari computers.

 

Have you even taken the time to look at this thread, which is just one of many ways of using Atari graphics? https://atariage.com/forums/topic/200118-images-generated-by-rastaconverter/?tab=comments#comment-2556201

 

It’s just confusing and difficult to understand the crazy-ass ways graphics can be done on the Atari 400 / 800

[Gunstar]

And because it's so awesome how Atari 8-bits do graphics, it can take a life-time to figure it all out!  I've had my Atari for 34 years, using it for graphic art and I still see new ways of using Atari graphics nearly every day!

 

It's why I could care less if other 8-bits can have more and better sprites, there's so much more beyond sprites to Atari graphics! I say Keep your sprites, give me 256 colors, 14 hardware graphic modes, many, many more mixed and software modes, too much to go over in just one thread. I can do so much more with my Atari as an artist than I could dream of doing on any other 8-bit. P/M graphic (sprites) are just another bonus!

Edited July 13, 2019 by Gunstar

[PixelCrunch]

Okay, so which mode of graphics were used, Standard or D.P Mode?

[flashjazzcat]

Mode 11 intrinsically presents all sixteen colours at the luminance dictated by bits 0-3 of the background colour register.

 

Mode 10 would probably be the most useful of the 'GTIA special' modes were it not for the shortage of colour registers, which results in nine usable colours (without mid-line register changes, etc) instead of sixteen. Lastly, mode 9 allows all sixteen luminance values in a single colour hue. A series of compromises: one can either have all the colours (mode 11) or all the luminances (mode 9), or just over half the ideal number of freely selectable colours (mode 10). One might complain about the C64's fixed colour palette, but it wasn't the only machine to make compromises.  Sadly they didn't implement a bitplane version of mode 7 with - at the very least - nine freely selectable colours (using 2 bits on the first scan line plus 2 bits on the second) instead of four.

 

Among things that were 'new' to me during recent years are mode 15 PAL blending, and the pleasing hi-res tritone effects possible with player/missile graphics underlays (U1MB BIOS setup menu being one example).

[Gunstar]

@PixelCrunch  do a search for my images in the Rastaconverter thread...

 

Never mind, easier said than done, you can search for author in advanced search, but apparently not within a specific topic. At least I couldn't figure out how...

 

Just start at the last page of the Rastaconverter thread and work your way backwards, my images are all within the last couple years and about the last half of the pages...

Edited July 13, 2019 by Gunstar

[kiwilove]

Something so obvious which hasn't been stated - is that graphics for a static screen is one thing, and graphics within a game another, so too for graphics within a demo.  That so-called tricks can be done to enhance the image - to what is presented.

 

Harvey

[Gunstar]

I think not stated because it IS obvious. Though maybe not to @PixelCrunch and it is his thread, so good point. 

 

For me, the static screens are the most important, being an artist. That's why sprite graphics aren't a priority to me in what a system offers graphically. Though they do come in handy for Rasta and G2F graphics.

 

I wonder why there aren't some graphic art programs for the Atari that offer the use of P/M's for additional colors in static graphics? Of course one or two are needed for a cursor/brush, but really just some missiles I would think, leaving 4 players and 1 or more missiles for the screen art...I always have been dismayed that so few graphic paint programs even offer DLI's and multiple resolutions...and the few that do, most only joystick input!

 

Once I'm competent enough as a programmer, I think my first serious program will be a paint program that offers all graphic modes, some mixed and software modes, DLI's, P/M enhancements and input for mouse/trackball/touch-tablets. But that is probably a year or two down the road still...any current programmers care to take up the torch?

Edited July 14, 2019 by Gunstar

[R0ger]

Some 'special' modes can be used in games too. Like that 4 colors hue/brightness interleaved mode. Here is small demo. It's character mode, 4 hues, 5 brightness levels, which makes 20 colors. No flickering, it doesn't go well with the movement.

 

Btw. this has the most complicated kernel handler I have ever written ?

pong.xex

Edited July 14, 2019 by R0ger

[emkay]

Here a link to Atarionline

 

http://atarionline.pl/v01/index.php?ct=nowinki&ucat=1&subaction=showfull&id=1563089433

 

Have a closer look at "Invasion" and Medical Machine" . Besides , the A8 pictures look all well, the two in particular use a bug of GTIA that allows to mix graphics modes in a scanline.

[R0ger]

9 minutes ago, emkay said:

Here a link to Atarionline

 

http://atarionline.pl/v01/index.php?ct=nowinki&ucat=1&subaction=showfull&id=1563089433

 

Have a closer look at "Invasion" and Medical Machine" . Besides , the A8 pictures look all well, the two in particular use a bug of GTIA that allows to mix graphics modes in a scanline.

Hm .. interesting ! The Medical Machine is quite clear, but that Invasion ? How is it done ?

[emkay]

4 minutes ago, R0ger said:

Hm .. interesting ! The Medical Machine is quite clear, but that Invasion ? How is it done ?

As such pictures need a kernel, or a lot of DLIs, it is not really a problem to set PMg positions, before and after the GTIA Mode switch.

Do there seems some line up on the ships over the "Planet/Moon" and the stars. You know, you can use PMg more than one time per scanline as well.  But it seems to set the start without re using any.

But it looks definitely great.  

[R0ger]

21 minutes ago, emkay said:

As such pictures need a kernel, or a lot of DLIs, it is not really a problem to set PMg positions, before and after the GTIA Mode switch.

Do there seems some line up on the ships over the "Planet/Moon" and the stars. You know, you can use PMg more than one time per scanline as well.  But it seems to set the start without re using any.

But it looks definitely great.  

Right, that might be. We will know when there is XEX released. I thought the mode transition is quite on the left side .. I did it in Sails of Doom splashscreen, and it wasn't so easy. But I did 2 mode changes per line, and here is only one, so it won't be that much of a problem it seems.

Edited July 14, 2019 by R0ger

[danwinslow]

23 hours ago, PixelCrunch said:

It’s just confusing and difficult to understand the crazy-ass ways graphics can be done on the Atari 400 / 800

yknow, I actually think this is part of why the A8 scene is still so active. The flexibility offered by the hardware allows people to come up with amazingly clever stuff, and it produces a real sense of accomplishment. If you use a machine that has a hard-defined and well known set of pre-determined graphics capability, then there's nothing to do. There isn't the same sense of the possible. So yeah, I agree, it's confusing and technically hard, but that's part of the draw. If all you want to do is plot pixels in colors then there's any number of modern machines available.

 

Edited July 14, 2019 by danwinslow

[emkay]

Yeah. There is a lot potential to discover. But there also limits reached. Atari Blast is such a limit, depending on horizontal shooter games. I can tell you Paul Lay has used every possible trick to get that quality there.

[emkay]

Pixelcrunch

 

 

What would you expect to say "hey the Atari blowed my mind" exactly?

There is a lot potential undiscovered in ego view (2nd and 3rd person view) . And, yet vertical scrolling isn't also fully developed. Presentation in Demos also didn't reach the hardware limits yet.

 

[zzip]

On 7/13/2019 at 3:58 PM, PixelCrunch said:

It’s just confusing and difficult to understand the crazy-ass ways graphics can be done on the Atari 400 / 800

It boils down to this:

The Atari has a number of pre-defined graphics modes that all have annoying limits, but none generally exceed 8K RAM in screen memory

 

But it also has:

Player missile graphics (sprites) that can add colors, but they are only 8-bits wide, but run the length of the screen (8x240 basically)  Up to 5 players, with 5 unique colors

Display List: Each line of your display can easily be reprogrammed to be a different mode than the previous line, this allows interesting mixed modes

 

ok, but even with that it is still a bit limiting.  Here are the coding practices used to enhance the colors:

 

Display-list interrupts:  These allow you to run a small amount of machine code in-between the time lines are drawn on screen.   You can use this to change the entire color palette for the next line, or reposition a Sprite horizontally (giving the impression that there are more than 5 sprites)

Vertical Blank Interrupts:  Allow you to run code in between screen draws--   you could point the display at a new memory location each one, flashing between two different images rapidly to give the illusion of more colors

cycle counting:  Neither of the above interrupts allow you to change the palette in the middle of a line draw,  but with carefully timed machine code, you can do just this and put more colors on a single line, or make a sprite appear in two places at once.   This is probably the hardest technique of the three.

 

Clever people mix the above techniques to create innovative approaches to graphics.

 

I remember in the 80s, I always felt limited by the 8-bit's graphics capabilities.   But we also had very limited graphics tools.   If we had something like Rasta back then, it would have blown my mind.