Anti-Aliasing
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Contents

Article : Anti-Aliasing
Date : 11/07/05
Page : 3
Reviewed By : ThePanther

Anti-Aliasing is a term used lots when selling graphics cards, but what exactly is Anti-Aliasing? We look deeper into the reasoning behind Anti-Aliasing and why we need it in the first place. There are varying types of anti-aliasing producing different results and different levels of performance hit.

Multisampling

Multisampling is a more efficient but slightly less pretty form of Anti-Aliasing. Multisampling takes multiple samples for each pixel. In a fairly standard example the quincunx system takes 4 samples in the corners and 1 sample in the middle. Each of these samples is given a weight the corners are given a weight of 1/8 each and the centre sample is given a weight of 1/2. the colour of the pixel is then determined by similar calculations to Supersampling.

With multisampling each cell on has two samples in it. Looking at the diagram below you can see that the other 3 samples are taken from neighbouring cells. So multisampling takes into account the colours around the pixel in question. This is how you get a blend of colour to achieve the desired result. It is important to note that Multisampling only happens when a cell is covered my more than one colour, otherwise a single colour is chosen and does not need to be calculated.

Levels of Anti-Aliasing

This refers to the amount of samples taken to determine the colour of the pixel. The higher the sample rate the better the quality of picture but the slower the image will be rendered. FSAA will be referred to as FSAA 2x or FSAA 4x, 6x and 8x are available but have too great a performance hit to be truly useful.

      

The image on the left shows samples taken from a graphics card using FSAA 2x, two samples are taken in two corners and used to produce the pixels colour. With FSAA 4x on the right you simple double the amount of samples taken for each pixel from FSAA 2x. when this is done on every pixel along an edge, the blending is much smoother and even less noticeable. As always though the trick is to balance quality and performance for your individual machine.

Pro's and Cons - The Summery

There are pro's and cons for using anti-aliasing in both games and applications. We have been through them but here is a quick summery to help you make up your mind if using AA or FSAA is right for you and your PC

Pro's

  • Smoothes out screen fonts
  • Rounded edges look to have smooth curves
  • Type can be easier to read due to better quality fonts
  • Games look a lot prettier and more realistic

Cons

  • Small text can be too blurred to read
  • already sharp edges can be made fuzzier
  • You cant print out Anti-Aliased text as it blurs
  • Static image sizes are larger
  • Games are affected by lower frame rates

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