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FSAA - What is it? Why do we care?

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FSAA - What is it? Why do we care?
Posted by CaTaLyST
Posted 07-13-2005

FSAA (full scene ANTI Aliasing): What is it? FSAA is a feature of most newer 3D cards that smooth out any rough edges that appear on screen. ATI and nVidia were pioneering this technology back in 2000. However, at the time, many critics were of the mindset that FSAA was not a suitable compensation to high-resolution image.

FSAA support: Hardware vs. Software
There are two types of FSAA support; Hardware FSAA, or software FSAA. Well, by hardware, we are talking about suport within the chipset, instead of software enabled support through the device drivers.

Through each type, the end result is similar. The image is less jagged do to a simulated 'blur'. To accomplish this, the card renders "X" times as many pixels as determined by the FSAA algorithm. For example: you select 2 Sample FSAA in your ATi Drivers. This causes the card to in effect have 1/2 its normal fill rate, because it is rendering 2x as many pixels at a given time. With 4x you take a 1/4 fill rate hit. Through this, the card is able to create a smooth out the hard edges. The key here is that images are not sharper, but are much smoother.

http://fix-it.org/forums/attachment...hmentid=6&stc=1
NO FSAA

http://fix-it.org/forums/attachment...hmentid=5&stc=1
FSAA

ATI's Radeon supports FSAA out of the box. The Radeon supports an FSAA method called "Super sampling". What this means is that it takes the frame, multiplies the values by you selected setting. (example 2). It then takes that new frame and samples it back down to its original resolution. In other words, a game played at a resolution of 640 x 480 is sampled 2x and the frame is now 1280 x 960. This new frame is then sampled back to the original 640 x 480 image. It sounds like the image was blown up and shurnk again, so how does this method improve image quality? Well, when this type of FSAA shrinks the image back down, all of the previously jagged edges were re-rendered and now are various shades of color, instead of being the old color that produced the jagged edge.

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by PCJ on 07-14-2005, 03:09 AM

Great article. Very easy to understand IMO. I think that eventually (this will take a lot of time), each of our glossary terms should link to an article like this one.

by gurutoo on 07-27-2006, 05:14 PM

Well written and easy to comprehend. Good job!

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