Anti-Aliasing

• When high resolution images are presented in a lower resolution causes visual defect in digital images like jagged (or) stair-stepped lines called Aliasing. 
• To reduce that visual defects and to make that jagged (or) stair-stepped lines smooth Anti-Aliasing method is used.
• Jaggies appear when an output device like monitor does not have a high enough resolution to represent a smooth line correctly.
• The pixels that makes up the screens of the monitor are all shaped in rectangles (or) squares.
• Smoothing the jagged appearance of diagonal lines in a bitmapped image.
• These effect can be minimized by increasing the resolution of the monitor, making the pixels small enough that the human eye cannot distinguish them individually.
• A single image pixel may be take up many monitor pixels, it is impossible for a lower resolution monitor to mask the jagged edges. This is where anti-aliasing required.
• This method removes jagged edges by adding subtle color changes around the lines, tricking the human eye into thinking that the lines are not jagged.
• The slight changes in color around the edges of a image help the line blend around curves, giving the impression that the line is true.

• Different types of Anti-aliasing methods used in computer games are:

     1. SSAA (Super sampling anti-aliasing):

• It was the first type of anti-aliasing available. It is useful on photorealistic images, but is not very common in games any more, because it uses so much processing power.

     2. MSAA (Multi sample anti-aliasing):

• It is used in modern games. It is only smooths out the edges of the polygon, not anything else. Low power processing power compared to SSAA.

     3. CSSA and EQAA (Coverage sample anti-aliasing and Enhanced quality anti-aliasing):

• These two types are similar to MSAA, but fraction of performance cost.

     4. FXAA (Fast approximate anti-aliasing):

• It has very small performance cost. Smooths out the edges in all parts of the image. But it makes the image look blurry.

       5. TXAA (Temporal anti-aliasing):

• It only works on certain newer graphics cards, but combines lots of different techniques to smooths out the edges. It is better than FXAA, but still has blurriness to it, and uses processing power.