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The Simple Antialiasing and Anisotropic Guide

By Koroush Ghazi from Jan 10, 2004 @ 23:00 CST

Before Going Any Further


Before you go any further in this guide, there is something very important you should note. This guide contains many screenshots designed to demonstrate the differences in image quality between various levels of Antialiasing and Anisotropic Filtering. To do this successfully, the screenshots herein are presented in three formats:


400x300 JPG Images - these are the ones that are loaded up with every page. They are not very good for seeing image quality differences, both because of their size and because the JPG picture format is lossy - i.e. the image is not as good as the original.


Fullsize JPG Images - when you click on the small images, you will see a fullsize JPG picture, which will show up image quality differences much more clearly. Again there are still some issues associated with the blurring and quality loss which comes with the JPG format.


Fullsize PNG Images - for the purist an option is presented under each image to view it as a fullsize PNG picture, which is a lossless format - meaning what you see should be exactly what appeared on my screen when I took the screenshot. This is the best way to examine and compare image quality, particularly at higher levels of AA/AF. The downside is that the PNG files are quite large, ranging from 500kb up to 2MB.


Most importantly of all though, to view the images in all their glory if you're using Internet Explorer, go to Tools>Internet Options>Advanced and under the Multimedia section untick the option "Smart Image Dithering" as this automatically blurs online images in an attempt to make them look smoother. Also, if you download any of the images, use something other than Windows Picture and Fax Viewer (the default picture viewer in WinXP) to view the pictures. The Windows Viewer also dithers (blurs) images. Use a professional application like Photoshop, or even Microsoft Photo Viewer or Microsoft Paint to fully experience the image quality. You can do this by right-clicking on the image and choosing "Open With...", then selecting something other than Windows Picture and Fax Viewer for example.


I know it seems strange to put this notice right at the start of the guide, but quite frankly it's pointless reading a guide about Antialiasing and Anisotropic Filtering if you cannot view the true image quality differences clearly for yourself.


Simple Definitions


Alrighty then, as promised here are the simple, straightforward definitions of Antialiasing and Anisotropic Filtering.


Antialiasing: Also called Full Screen Anti-Aliasing (FSAA) or simply Antialiasing (AA) for short. As the name implies, this is a method which counteracts the effects of aliasing. What's Aliasing? Well aliasing is the jaggedness and pixelation you see on computer images - particularly noticeable on things like the straight edges of walls, or the outline of buildings and terrain in 3D games. These jagged edges can even "sparkle" somewhat when you are moving around in a 3D environment. That effect can be overcome in two ways: by increasing the resolution at which your game displays (e.g. from 640x480 to 1024x768), and by the use of Antialiasing, or both. When AA is enabled, it uses your graphics card's hardware to blend the edges of the jagged lines and hence produce a smoother image.



The higher the level of Antialiasing applied (usually in steps of 2x, 4x, 6x and 8x), the progressively smoother the image, but the greater the strain on your graphics card in recalculating the image to produce these smoother images. Also, the higher the level of AA the greater the blurriness you may notice, and the graphics may in fact become too "cartoon smooth" in appearance.


While this is a relatively simple definition, other definitions of Antialiasing, including those which are more technical can be found here, here, here and here.


Anisotropic Filtering: Also referred to simply as Anisotropic (or AF) for short. This is a method which makes textures (the surfaces of all 3D objects) appear cleaner and crisper. Raising the resolution of a game is one way of improving texture appearance, however textures receding into the distance may still become noticeably blurry and their finer features may become indistinguishable even at very high resolutions. Anisotropic Filtering is used to enhance the details of textures, and to reduce the blurriness which occurs on textures that are further away.


Examine the two screenshots below, paying particular attention to the grid pattern in the distance. Clearly the use of high level Anisotropic Filtering in the lower image has removed virtually all the blurriness visible in the top image, particularly for more distant textures.



[Click on image for fullsize JPG or click here for fullsize PNG]


The higher the level of Anisotropic Filtering applied, the clearer the textures will appear, but the greater the strain on your graphics card in filtering the image to produce the clearer representation of textures. Also, at very high levels of AF the clarity of distant textures may be unrealistically high.


While this is a relatively simple definition, other definitions of Anisotropic Filtering, including those which are more technical can be found here, here, here, and here.


Ok, so that wasn't too painful to read through, was it? I think it's pretty clear that in gaming you use AA to reduce the "jaggies", while you use AF to sharpen up blurry surfaces. Obviously the two can be combined to produce 3D graphics with both smooth outlines and crisper surfaces.


The next section concentrates on how you can accurately adjust your AA and AF settings for your particular graphics card, and what the different settings mean.

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