@Iain Peet: The problem with computer graphics is, that the signal is not band-limited and therefore the nyquist-theorem doesn't hold. Imagine the simple step function (one black pixel adjacent to a white pixel). This function is not band-limited and therefore you cannot sample at a high enough rate to correctly reconstruct the signal. Therefore, the bitter truth for computer graphics is that anti-aliasing is always a bit of a "hack" - you can only approximate the truth. But that's not too much of a problem since in computer graphics (especially games) it only has to "look good" not "correct" (in the mathematical sense). As a result, it makes most sense to treat computer graphics within an error-framework rather than the "nyquist-framework". It's better to ask the question "how close am I to the truth?" instead of "How do I reconstruct the truth?" I recommend Michael Unser's excellent paper "Sampling - 50 Years After Shannon" for a very nice theoretical background overview on that topic.