Bitmaps page 3
Dithering is not often encountered in animation work, but you should understand the term.
If it only used 24 colours / shades, it would look like this:
As you can see, the result is very poor and the limited number of colours / shades very obvious. However, by dithering the pixels, we can get a more reasonable looking picture:
The sphere is still not smoothly shaded, but it is pretty good in view of the fact that we have only used 24 colours instead of 16 million!
The way the trick is accomplished by the software is seen by looking at a small part of the sphere near the top and blowing the image up:
Dithering, as its name implies, is a way
of scattering pixels at random to cheat the eye into seeing more
colours than are really there - a technique first invented by the
Impressionist painters. You will probably not encounter dithering
Antialiasing is a technique used to smooth edges
in bitmap images.
...it looks as though the yellow arrow shape is
smooth, even though there are relatively few pixels making up the
image. (In fact 150 x 150).
Pixels made by mixing between the foreground and
background colours are added around the boundary edge - giving a
softened, blended look.
Without the antialiasing, the full sized image would look a little rougher...
...blow up the image now and you will see the horrible raggedy line of the unantialiased pixels:
Most of the time, you will want to leave antialiasing switched on when offered a choice.