Anti-Aliasing
Sand down those jaggies
By Stephen Orgill
You will of all heard of the phrase Anti-Aliasing when talking about computer games
or graphics cards. You are told about what level of anti-aliasing your card can
achieve but do you really know what anti-aliasing does or do you just accept it as
a good thing and go for the best one? In this article we will show you what
Anti-Aliasing actually does and show you why its important to graphics in images
text and games. We will also go into details about what side effects anti-aliasing
has in games and why you have to strike a compromise between a high level of
anti-aliasing and the performance of your computer.
What is Anti-Aliasing?
The letter on the left is a blown up letter a with no anti-aliasing. The letter on
the right has had anti-aliasing applied to it. In this blown up form it looks like
its simply blurred but if we reduce the size down to a more standard size you may
see the difference.
Now look closely at the two letters. You can still tell that the letter of the left
is jagged but the letter on the right looks a lot smoother and less blurry than the
example above. Remember I have only shrunk the image down back to normal size and
have not altered anything else to the image at all. So as you can see, Anti-Aliasing
bring a much more pleasing image to the eye. Something like what come out of a high
class printer rather than what you can be used to seeing when on a computer screen.
Why do we get jagged edges on our graphics?
Jagged edges are cause by limitations in a computer screen, whether that be a CRT or
TFT/LCD screen its all the same. Monitors are capable or producing nearly perfect
straight lines either horizontally or vertically, but when it comes to diagonal lines
of any angle your monitor is not capable of producing a line without some jagged edge.
This is because your screen is made up of pixels in a grid formation. When you draw
a diagonal line on a computer screen it has to cross several grid lines, because
pixels create blocks of colour diagonal lines displace these blocks slightly causing
jagged edges, Check out the following example to see what happens on your screen.
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