What does anti-aliased mean? - Tilted Forum Project Discussion Community

Mondak · 07-18-2003, 06:43 PM

I have seen this in two situations

1 - My videocard controls I think said something about this.

2 - In Photoshop, I have the option of turning this on or off when it comes to text

Can someone please explain to me what this is and what it is doing in each situation.

Thanks very much.

yakimushi · 07-18-2003, 06:49 PM

Yep.

AA is basically blurring the edges on things so you can't see the pixels quite so much, "jaggys".

AA algorithms use a combination of pixel averaging on the geometry as well as better usage of blending.

Overall it just makes things look nicer.

You do take a performance hit in games though, so you might want to play with settings a bit so you get the best image quality / performance balance.

lumpenprole · 07-18-2003, 06:50 PM

Anti-aliasing is how jagged your fonts look. AA fonts are blurred mathematically to look a bit more smooth. However, sometimes they just look blurry. Rather depends on the app. Most of the Adobe apps do fine with them, but for gods sake stay away from it in Flash.....

Raw Kuts · 07-18-2003, 06:52 PM

It is a way to get rid of jagged edges. In a video game, if you have a straight edge that is diagonal, you will usually see a stair case like line. To get rid of this, anti aliasing renders the image at a higher resolution than you are running the game at (say you play at 800x600, 2x anti aliasing will render the scene at 1600x800 and then sample pieces of that scene to show you).

With text, what it does it blur the edges of the text when you are using a large font. If you have a black "A" on a white background w/o antialiasing then you will only see the A as black, and the background as white. If you put anti aliasing on, then the A will be black, but around it, there will be shades of grey to smooth out the jaggies.

I am pretty sure this is an accurate definition of anti aliasing, but I have been know to be very wrong on these kinds of thing, so someone correct me if they see fit.

Mondak · 07-20-2003, 07:07 PM

Not bad at all - this is a great example of why the TFP is such a cool place. Someone just check the time stamps to see that. Thanks a lot to all of you. I honestly feel enlightened.

JStrider · 07-20-2003, 07:38 PM

well since theyve said what it is... ill tell ya how to see for yourself....

go into photoshop pick a nice curvy font... and set the size up so one letter fills up most of the screen then change the settings for the AA to none... and then the other options
and you can see the edges getting smoother... or less smooth depending on which way your changing it

0count · 07-21-2003, 08:05 AM

Also, to add to the 3D AA explanations: The "old" AA systems use the anti-aliasing on the whole picture, thus using a lot of effort to smoothen things that don't need it. The never systems from ATI and NVIDIA(?) can find the places that need anti-aliasing in one frame and then use the AA in only those parts of the frame.

digby · 07-21-2003, 10:37 AM

woo hoo! physics lecture time! since everyone else answered the practical side, I'll try to explain what's going on behind the scene.

-note: if you don't care about sampling and recovery, and other aspects of applied digital electronics, you can skip this post and save yourself a headache.

Aliasing is an undesirable by-product of all digital to analog conversions. Because all data is stored at discrete values, you get that "jaggedness" in what would otherwise be a continuous function.

For example, imagine a sine wave. When sampled and restored, you would have something that looks like a bunch of ascending and descending stairs. From a mathematical standpoint, this is a construct of an infinite number of odd harmonics (multiples of the fundamental frequenct of our sine wave).

An anti-aliasing filter is a low-pass filter that (in theory) begins to operate just above the frequency of our original sine wave. This removes all those extra, unwanted frequencies and gives us a very close approximation of our original input signal.

I apologize if this isn't the most thorough explantion. I'm trying to pack about 4 weeks of digital theory lectures into a short little paragraph. Let me know if you need clarification.

[edit]I know all that stuff, but I still can't spell.[/edit]

Cynthetiq · 07-21-2003, 02:51 PM

it's those damned jagged diagonal lines.... ARRRGH!!!!

bermuDa · 07-21-2003, 03:59 PM

aliasing is the jaggies, anti-aliasing blends the color values on either side of the line to reduce aliasing. This is finally becoming a real option in games thanks to the newer graphics cards, like ATI's Radeon 9700 and 9800 cards, and Nvidia's nv35 chipset.

Garbalo69 · 07-23-2003, 07:36 AM

Anti-Aliasing, now Full Screen Anti Aliasing, is simply a filter that, depending on the algorithm used, it sort of creates a second image over the first one, slightly moved and blurred, many many times. It creates the illusion that the jaggies are reduced.

I LOVE FSAA

wasapeas · 07-23-2003, 02:56 PM

Crappy twist to the story: FSAA will be borked for Half Life 2 and many future games for most of the recent NVidia cards =(

http://www.shacknews.com/ja.zz?comments=27557

ChipX86 · 07-24-2003, 12:59 PM

Most of the people here answered what antialiasing is, and a couple offered some theory. I could get into the details of that theory, algorithms used, but instead I'll discuss something that I don't think has been talked about in this thead: sub-pixel anti-aliasing.

Sub-pixel anti-aliasing, also known as ClearType nowadays, was actually invented many years ago. Apple used it on their old monitors for some games. The concept is simple. You take a pixel on the screen and divide it up into three sub-pixels. This is more effective on PDAs and LCD monitors, where each pixel actually is composed of tiny red, green, and blue cells in one of a couple different patterns that can be turned on or off to varying levels of brightness. In a standard CRT monitor, the color is more "sprayed" into the pixel, to put it simply.

If you have Windows XP around, turn on ClearType in the antialiasing options (I think it's in the desktop properties dialog somewhere). If you look close at the screen, you'll notice little colors around the text. This will be more apparent on a standard CRT monitor than a flat screen LCD monitor. Here's why you see the colors.

Imagine your pixel as a box like this: []. On an LCD, it's really more like this: [][][]. The cells inside the pixel are usually in RGB (Red Green Blue) arrangement, though other arrangements are also used on some screens. When you turn anti-alias a line, you'd typically have that pixel (all 3 sub-pixels) set to black, and the pixels to the left and right may be a shade of grey to have the illusion of the line being anti-aliased. This takes 3 pixels. However, with sub-pixel anti-aliasing, your horizontal resolution, anti-aliasing-wise, triples. Instead of using 3 pixels, you can have the middle pixel set to black and the left and right set to a shade of their color, for a very thin line, or that pixel can be black and the right-most sub-pixel on the pixel to the left can be set to a shade of its blue, and the left-most sub-pixel on the pixel to the right can be set to a shade of red.

Did that make sense? :/

Anyhow, if you use an LCD screen (laptop or flat panel monitor, or some PDAs), try enabling ClearType. Even if you have a CRT monitor, check it out. It's really nice, and improves the quality a bit, though in some cases you'll see some color poking out around the side

You can find more information and some examples of the pixel arrangements, as well as quality comparisons by doing a search on Google for "Richard Leader" and "ClearType". Somewhere, he has a site with some nice examples and detailed information.

That ended up longer than I thought it would.

07-18-2003, 06:43 PM	#1 (permalink)
Mondak Industrialist Location: Southern California	What does anti-aliased mean? I have seen this in two situations 1 - My videocard controls I think said something about this. 2 - In Photoshop, I have the option of turning this on or off when it comes to text Can someone please explain to me what this is and what it is doing in each situation. Thanks very much.

07-18-2003, 06:52 PM	#4 (permalink)
Raw Kuts Insane Location: San Diego, CA	It is a way to get rid of jagged edges. In a video game, if you have a straight edge that is diagonal, you will usually see a stair case like line. To get rid of this, anti aliasing renders the image at a higher resolution than you are running the game at (say you play at 800x600, 2x anti aliasing will render the scene at 1600x800 and then sample pieces of that scene to show you). With text, what it does it blur the edges of the text when you are using a large font. If you have a black "A" on a white background w/o antialiasing then you will only see the A as black, and the background as white. If you put anti aliasing on, then the A will be black, but around it, there will be shades of grey to smooth out the jaggies. I am pretty sure this is an accurate definition of anti aliasing, but I have been know to be very wrong on these kinds of thing, so someone correct me if they see fit. __________________ ( o< --!"Take that bass out you're voice, you talk to me in treble." / / \ \/_/_ -->Mos Def

07-20-2003, 07:07 PM	#5 (permalink)
Mondak Industrialist Location: Southern California	Not bad at all - this is a great example of why the TFP is such a cool place. Someone just check the time stamps to see that. Thanks a lot to all of you. I honestly feel enlightened. __________________ All truth passes through three stages: First it is ridiculed Second, it is violently opposed and Third, it is accepted as self-evident. ARTHUR SCHOPENHAUER (1788-1860)

07-20-2003, 07:38 PM	#6 (permalink)
JStrider Poo-tee-weet? Location: The Woodlands, TX	well since theyve said what it is... ill tell ya how to see for yourself.... go into photoshop pick a nice curvy font... and set the size up so one letter fills up most of the screen then change the settings for the AA to none... and then the other options and you can see the edges getting smoother... or less smooth depending on which way your changing it __________________ -=JStrider=- ~Clatto Verata Nicto

07-21-2003, 10:37 AM	#8 (permalink)
digby Crazy Location: Ahh, the lovely South	woo hoo! physics lecture time! since everyone else answered the practical side, I'll try to explain what's going on behind the scene. -note: if you don't care about sampling and recovery, and other aspects of applied digital electronics, you can skip this post and save yourself a headache. Aliasing is an undesirable by-product of all digital to analog conversions. Because all data is stored at discrete values, you get that "jaggedness" in what would otherwise be a continuous function. For example, imagine a sine wave. When sampled and restored, you would have something that looks like a bunch of ascending and descending stairs. From a mathematical standpoint, this is a construct of an infinite number of odd harmonics (multiples of the fundamental frequenct of our sine wave). An anti-aliasing filter is a low-pass filter that (in theory) begins to operate just above the frequency of our original sine wave. This removes all those extra, unwanted frequencies and gives us a very close approximation of our original input signal. I apologize if this isn't the most thorough explantion. I'm trying to pack about 4 weeks of digital theory lectures into a short little paragraph. Let me know if you need clarification. [edit]I know all that stuff, but I still can't spell.[/edit] __________________ mmmm.... pudding Last edited by digby; 07-22-2003 at 05:59 AM..

07-18-2003, 06:49 PM	#2 (permalink)
yakimushi Addict	Yep. AA is basically blurring the edges on things so you can't see the pixels quite so much, "jaggys". AA algorithms use a combination of pixel averaging on the geometry as well as better usage of blending. Overall it just makes things look nicer. You do take a performance hit in games though, so you might want to play with settings a bit so you get the best image quality / performance balance.

07-18-2003, 06:50 PM	#3 (permalink)
lumpenprole Upright	Anti-aliasing is how jagged your fonts look. AA fonts are blurred mathematically to look a bit more smooth. However, sometimes they just look blurry. Rather depends on the app. Most of the Adobe apps do fine with them, but for gods sake stay away from it in Flash.....

07-21-2003, 08:05 AM	#7 (permalink)
0count Upright	Also, to add to the 3D AA explanations: The "old" AA systems use the anti-aliasing on the whole picture, thus using a lot of effort to smoothen things that don't need it. The never systems from ATI and NVIDIA(?) can find the places that need anti-aliasing in one frame and then use the AA in only those parts of the frame.

07-21-2003, 02:51 PM	#9 (permalink)
Cynthetiq Tilted Cat Head Administrator Location: Manhattan, NY	it's those damned jagged diagonal lines.... ARRRGH!!!! __________________ I don't care if you are black, white, purple, green, Chinese, Japanese, Korean, hippie, cop, bum, admin, user, English, Irish, French, Catholic, Protestant, Jewish, Buddhist, Muslim, indian, cowboy, tall, short, fat, skinny, emo, punk, mod, rocker, straight, gay, lesbian, jock, nerd, geek, Democrat, Republican, Libertarian, Independent, driver, pedestrian, or bicyclist, either you're an asshole or you're not. What's the best nation in the world? DO-NATION!

07-21-2003, 03:59 PM	#10 (permalink)
bermuDa don't ignore this--> Location: CA	aliasing is the jaggies, anti-aliasing blends the color values on either side of the line to reduce aliasing. This is finally becoming a real option in games thanks to the newer graphics cards, like ATI's Radeon 9700 and 9800 cards, and Nvidia's nv35 chipset. __________________ I am the very model of a moderator gentleman.

07-23-2003, 07:36 AM	#11 (permalink)
Garbalo69 Tilted	Anti-Aliasing, now Full Screen Anti Aliasing, is simply a filter that, depending on the algorithm used, it sort of creates a second image over the first one, slightly moved and blurred, many many times. It creates the illusion that the jaggies are reduced. I LOVE FSAA

07-23-2003, 02:56 PM	#12 (permalink)
wasapeas Upright	Crappy twist to the story: FSAA will be borked for Half Life 2 and many future games for most of the recent NVidia cards =( http://www.shacknews.com/ja.zz?comments=27557

07-24-2003, 12:59 PM	#13 (permalink)
ChipX86 Tilted	Most of the people here answered what antialiasing is, and a couple offered some theory. I could get into the details of that theory, algorithms used, but instead I'll discuss something that I don't think has been talked about in this thead: sub-pixel anti-aliasing. Sub-pixel anti-aliasing, also known as ClearType nowadays, was actually invented many years ago. Apple used it on their old monitors for some games. The concept is simple. You take a pixel on the screen and divide it up into three sub-pixels. This is more effective on PDAs and LCD monitors, where each pixel actually is composed of tiny red, green, and blue cells in one of a couple different patterns that can be turned on or off to varying levels of brightness. In a standard CRT monitor, the color is more "sprayed" into the pixel, to put it simply. If you have Windows XP around, turn on ClearType in the antialiasing options (I think it's in the desktop properties dialog somewhere). If you look close at the screen, you'll notice little colors around the text. This will be more apparent on a standard CRT monitor than a flat screen LCD monitor. Here's why you see the colors. Imagine your pixel as a box like this: []. On an LCD, it's really more like this: [][][]. The cells inside the pixel are usually in RGB (Red Green Blue) arrangement, though other arrangements are also used on some screens. When you turn anti-alias a line, you'd typically have that pixel (all 3 sub-pixels) set to black, and the pixels to the left and right may be a shade of grey to have the illusion of the line being anti-aliased. This takes 3 pixels. However, with sub-pixel anti-aliasing, your horizontal resolution, anti-aliasing-wise, triples. Instead of using 3 pixels, you can have the middle pixel set to black and the left and right set to a shade of their color, for a very thin line, or that pixel can be black and the right-most sub-pixel on the pixel to the left can be set to a shade of its blue, and the left-most sub-pixel on the pixel to the right can be set to a shade of red. Did that make sense? :/ Anyhow, if you use an LCD screen (laptop or flat panel monitor, or some PDAs), try enabling ClearType. Even if you have a CRT monitor, check it out. It's really nice, and improves the quality a bit, though in some cases you'll see some color poking out around the side You can find more information and some examples of the pixel arrangements, as well as quality comparisons by doing a search on Google for "Richard Leader" and "ClearType". Somewhere, he has a site with some nice examples and detailed information. That ended up longer than I thought it would.