When a program renders a picture on a display device, it must
compute a color for each pixel on the display. Computing the color for
a pixel involves taking samples from the model or scene being drawn.
A display screen has a finite number of regularly-spaced pixels, which
means that a rendering program will take a finite number of samples
from the model. Aliasing occurs when the finite number of samples do
not contain enough information to draw an accurate picture of the
The next three slides demonstrate sampling.