Artifacting: Why use it?

[Urchlay]

Something I've been thinking about on and off for 20+ years...

 

Why does anyone write a game/demo/etc that uses GR.8 artifacts, instead of using GR.15/Antic E graphics?

 

The GR.8 and GR.15 modes use the same amount of memory, and both give you 4 displayable colors counting the background... but with a GR.8 display designed to use artifacting, you have a few disadvantages:

 

- No direct control over the artifacted colors (depends on the TV's color/tint settings, and/or which version of CTIA/GTIA is being used).

- Doesn't work on PAL (well, OK, there's such a thing as PAL artifacting, but it's totally different from NTSC, from what I've read. You'd have to totally redesign your graphics and create separate PAL and NTSC versions of your program).

- Doesn't work on monochrome monitors, or color monitors using the s-video (separate chroma/luma) signal. Even on a green or amber monitor, GR.15 can display 4 different shades of green/amber, but artifacted graphics just come out as closely spaced vertical lines... usually recognizable, but not attractive.

 

The only disadvantage of GR.15 mode I can think of right now is that the original OS in the 400/800 didn't directly support it, so you have to manually set up the display list (or modify the GR.8 display list) if you want to be compatible with the 400/800. I wouldn't think this would stop anyone but a beginning BASIC programmer from using it, though.

 

If you're mixing graphics and text, artifacting does let you use the standard GR.0 font wherever you want, I guess that counts as an advantage. To me, it doesn't seem like a good tradeoff for a game, unless it's a text-based game with just a few incidental graphics here and there.

 

(Everything I just said also applies to GR.0 vs. GR.12/Antic 4, too...)

 

So... why do people like artifacting? There's obviously no right or wrong answer, I'm just asking for opinions...

[Allas]

You forgot that Gr.8 let to display white pixels in hi-res 320x200.

Most of artifact color are display in 160x200. In the other side you can get until 9 colors if you know how to control the artifacting technique.

It's true PAL TV sets are in disaventage with artifact colors, but that isn't a reason to abandon new games or demos with artifact colors.

[potatohead]

As mentioned above, one can get more than 4 colors with artifacting. That's a good reason right there.

 

Texture is another. On monochrome screens, the different textures make things stand out.

 

If the object is the solid color, then it can be fully defined in the higher resolution. This can yield smooth movement, which is why so many early games featured a white ship, for example.

 

Text and detail. Having the option of addressing higher resolution pixels helps with this.

 

Overall appearance. Some graphics look good this way! So, it becomes a personal preference thing.

[Urchlay]

You forgot that Gr.8 let to display white pixels in hi-res 320x200.

 

Well, but not really... if you try to display one white pixel, you actually get a red, green, or blue artifacted pixel, double the width of your white pixel (so 160x200 is the effective resolution). If you try to draw something with white pixels, it ends up with color artifacts all over the place... On my Atari right now (XEGS, using composite), I'm looking at a GR.0 screen, and none of the characters look solid white.

 

Most of artifact color are display in 160x200. In the other side you can get until 9 colors if you know how to control the artifacting technique.

 

Hm, really? I only know how to get 4... or 5, counting the background, but the colors aren't independent (each pixel's color is partly determined by the pixels to the left/right of it, and partly by where it appears on the scanline).

 

It's true PAL TV sets are in disaventage with artifact colors, but that isn't a reason to abandon new games or demos with artifact colors.

 

Oh, I wasn't saying that... I was giving reasons why I, personally, wouldn't use artifacting... but I wouldn't tell anyone else what they should do!

[Fröhn]

- Doesn't work on PAL (well, OK, there's such a thing as PAL artifacting, but it's totally different from NTSC, from what I've read. You'd have to totally redesign your graphics and create separate PAL and NTSC versions of your program).

PAL artefacting doesn't work nearly as good as NTSC artefacting, that's why nobody used it

 

So... why do people like artifacting? There's obviously no right or wrong answer, I'm just asking for opinions...

With artefacting you could use some hires pixels. That's pretty much the only reason to use it.

[ZylonBane]

Well, but not really... if you try to display one white pixel, you actually get a red, green, or blue artifacted pixel, double the width of your white pixel (so 160x200 is the effective resolution).

That's why you DON'T DO THAT.

 

To effectively use the 320x200 resolution mode, you have to work around the artifacting. This means you have to avoid horizontal runs of even or odd pixels. Either pad single pixels with two or more blank pixels on the left and right, or have two or more in a row touching each other. The Atari's own built-in character set uses the latter technique.

[Gunstar]

You forgot that Gr.8 let to display white pixels in hi-res 320x200.

 

 

Most of artifact color are display in 160x200. In the other side you can get until 9 colors if you know how to control the artifacting technique.

 

Hm, really? I only know how to get 4... or 5, counting the background, but the colors aren't independent (each pixel's color is partly determined by the pixels to the left/right of it, and partly by where it appears on the scanline).

 

 

 

 

I have a gr. 8 art program (forget the name at the moment , but I'll find it) that lets you display around 9 colors (or more!). It depends on where you place the pixels to achieve different colors. The paint program has tools with the different patterns to automatically choose the colors you want, so you don't have to mess with it.

 

And as for why use artifacting, I, as an artist, thinks its FANTASTIC to be able to use the highest resolution on the 8-bit and have around 9 artifacted colors to use! I LIKE artifacted colors in games too, and if you don't, then just turn down the color! Simple as that. Oh, and S-video does NOT get rid of artifacted colors, though it does reduce them some so they are harder to see and the pixel patterns used to get the colors show up more because S-video is sharper, but the artifacting is still there. My C= 1080 monitor lets me use S-video, but it has a button to press on the back to revert it back to standard video, which I use depending on if I want a sharper image, or better artifacting colors.

Edited December 26, 2006 by Gunstar

[ZylonBane]

Oh, and S-video does NOT get rid of artifacted colors

Yes it does. Artifacting only happens due to the chroma and luma signals being combined. The conditions required to produce artifact colors DO NOT EXIST over an S-Video connection.

[Bryan]

Oh, and S-video does NOT get rid of artifacted colors

Yes it does. Artifacting only happens due to the chroma and luma signals being combined. The conditions required to produce artifact colors DO NOT EXIST over an S-Video connection.

 

Zylonbane is 100% correct. If you're using a Chroma/Luma connection and you're still getting artifact colors, then you've connected Composite Video to the Chroma jack.

 

-Bry

[mos6507]

I always thought artefacting was used only when a game was ported over from the Apple II.

[Bryan]

I always thought artefacting was used only when a game was ported over from the Apple II.

You know what bugs me is that GTIA contains 99% of what is needed to produce an actual 2 color high-rez mode. Atari decided that color changes would only be latched on color clock boundaries while luminance changes are clocked on every half-cycle, so we have the 1.5 color mode. A true 2-color mode would have given us some nice text options.

 

-Bry

[+remowilliams]

Oh, and S-video does NOT get rid of artifacted colors, though it does reduce them some so they are harder to see and the pixel patterns used to get the colors show up more because S-video is sharper, but the artifacting is still there. My C= 1080 monitor lets me use S-video, but it has a button to press on the back to revert it back to standard video, which I use depending on if I want a sharper image, or better artifacting colors.

As has been previously noted, s-video definitely gets rid of artifacting. It's one of the benefits of the higher bandwidth Y/C separated signal.

 

Though I do think I know what you are referring to with the C1080. I have a bunch of C1084 monitors, and (IIRC) if you connect a composite video signal to the Chroma input, instead of a proper separated chroma (i.e. one component of s-video) when switching the monitor back and forth between 'CVBS (composite) ' and 'LCA (s-video)' modes, the LCA mode will appear to be a sharper version of the standard composite signal. But it's not s-video

 

EDIT: OK, I guess I did recall correctly, now that I saw Bryan's other post above

Edited December 27, 2006 by remowilliams

[Urchlay]

I have a gr. 8 art program (forget the name at the moment , but I'll find it) that lets you display around 9 colors (or more!). It depends on where you place the pixels to achieve different colors. The paint program has tools with the different patterns to automatically choose the colors you want, so you don't have to mess with it.

 

If you find it, I'd be interested in messing with it. I've spent a good chunk of today with Atari BASIC and GR.8, trying to figure out how to get more than 4 or 5 colors. Even when I'm able to get 5 colors, two of them are so close together that I'm not 100% sure they're different colors

 

And as for why use artifacting, I, as an artist, thinks its FANTASTIC to be able to use the highest resolution on the 8-bit and have around 9 artifacted colors to use! I LIKE artifacted colors in games too, and if you don't, then just turn down the color! Simple as that.

 

Ehh, I wasn't trying to say I don't like artifacted colors, or that I didn't want to look at them. I just wanted to know why people choose artifacting over something like GR.15. Now I've got your answer... and it's a good one.

[Urchlay]

To effectively use the 320x200 resolution mode, you have to work around the artifacting. This means you have to avoid horizontal runs of even or odd pixels. Either pad single pixels with two or more blank pixels on the left and right, or have two or more in a row touching each other. The Atari's own built-in character set uses the latter technique.

 

Padding a single white pixel with two or more blank pixels on the left and right results in a purple or dark-green artifacted double-pixel, not a white pixel...

 

Two white pixels, padded with two blank pixels on the left and right, results in one double-pixel, either red or blue, depending on whether I start on an even or odd column.

 

The only way I'm ever able to see a single pixel of any color is to switch to s-video (which kills all artifacting effects, at least on my monitor).

 

I *am* able to get two different shades of purple, but the lighter one of them is made of 3 pixels in a row... and is displayed as being 4 GR.8 pixels wide (same size as one GTIA mode 9-11 pixel).

 

...hm, and I just now tried 3 pixels in a row starting on an even column, which appears as a lighter shade of green, and is actually 3 pixels wide.

 

All these tests were done on an XEGS hooked up to the composite input of a C=1702 monitor, with the text background black (poke 710,0).

 

So I can get 8 foreground colors on screen at once, plus a black background... but to use some of the colors, I have to give up lots of horizontal resolution, either by leaving blank padding pixels or by putting several lit pixels next to each other.

 

I still want to mess with Gunstar's paint program, I get the feeling I'm still doing something wrong.

 

Oh, and S-video does NOT get rid of artifacted colors

Yes it does. Artifacting only happens due to the chroma and luma signals being combined. The conditions required to produce artifact colors DO NOT EXIST over an S-Video connection.

 

Hm, could there be something wrong with a monitor that allows the signals to mix when they shouldn't? If I had an s-video setup, and I skinned the chroma and luma signal wires and shorted them together outside the monitor, or if I shorted the chroma and luma inputs together inside the monitor, would I see artifacts, or would I see a garbage picture, unusable?

 

Not that I think it would be a good idea, am just trying to understand what's going on...

[Goochman]

I was able to get:

 

white (duh )

blue

brown

green

yellow

purple

 

Yellow and Purple I stumbled across on the last Basic game I was working on back in the 80's.

 

What were the 9 colors you were able to get Gunstar?

 

Oh and why use artificating? It was a Basic programmers dream for me - Remapping the charset made it easy to create some colorful (somewhat) games easily - I didnt know how to map chars on to any of the graphic modes, so tile based charmaps were easy to create and manipulate for me

Edited December 27, 2006 by Goochman

[+remowilliams]

If I had an s-video setup, and I skinned the chroma and luma signal wires and shorted them together outside the monitor, or if I shorted the chroma and luma inputs together inside the monitor, would I see artifacts, or would I see a garbage picture, unusable?

If you tie luma/chroma directly together and stick it into a composite input, you'll get some rather crappy looking composite video I believe.

 

Not that I think it would be a good idea, am just trying to understand what's going on...

If you're talking about Gunstar's post - what's going on is what I posted previously ^ .

[Urchlay]

If you tie luma/chroma directly together and stick it into a composite input, you'll get some rather crappy looking composite video I believe.

 

I meant, connect the luma/chroma normally to the s-video luma/chroma inputs, then short the luma to the chroma, so the luma and chroma signals get mixed, and both luma and chroma appear on both inputs... would this even give a usable picture?

[mos6507]

I always thought artefacting was used only when a game was ported over from the Apple II.

You know what bugs me is that GTIA contains 99% of what is needed to produce an actual 2 color high-rez mode. Atari decided that color changes would only be latched on color clock boundaries while luminance changes are clocked on every half-cycle, so we have the 1.5 color mode. A true 2-color mode would have given us some nice text options.

 

-Bry

 

I agree. Only having two brightnesses of one hue available in Gr.0/8 is probably the most annoying limitation in the A8 chipset.

[Gunstar]

Oh, and S-video does NOT get rid of artifacted colors

Yes it does. Artifacting only happens due to the chroma and luma signals being combined. The conditions required to produce artifact colors DO NOT EXIST over an S-Video connection.

 

Zylonbane is 100% correct. If you're using a Chroma/Luma connection and you're still getting artifact colors, then you've connected Composite Video to the Chroma jack.

 

-Bry

 

It may be due to an old monitor, as I do have it hooked up via chroma/lumina jacks and it is definately sharper and most artifacting does not work, at least not as intended, but there is still slight blue&red artifacting only a little bit, it's not nearly as noticable as regular composite. it gets rid of 95% of the color and nothing but blue and red (depending on tint). But I haven't hooked it up on my TV or anything to see if that S-video is clearer. I may have not have been as clear on how little artifacting there is. Obviously there's no edge crawl and the display is much sharper still on my old 1080s. I could see where newer monitors or TV's with S-video would be even sharper and no NTSC artifacting shows up on them at all. I know S-video on my TV doesn't artifact with other video sources. So maybe it does the same with the 8-bit chroma/lumina.

Edited December 27, 2006 by Gunstar

[ZylonBane]

You know what bugs me is that GTIA contains 99% of what is needed to produce an actual 2 color high-rez mode. Atari decided that color changes would only be latched on color clock boundaries...

Atari decided no such thing. The artifact colors in GR.0 and GR.8 are exactly that-- artifacts. They are not intentional effects, they are unintentional side-effects.

 

As an aside, for some reason you can get noticeably more pure artifact colors if you run an "inverted" display-- set the foreground color to dark and the background color to bright, then fill the entire display and draw by erasing pixels instead of setting them.