When a large part of the texture
corresponds to a single pixel in the framebuffer, simple filtering may give
strong aliasing artefacts. In
animations, scintillation (shimmering) artefacts may also appear.

Would prefer to average texels over
a large area of the texture. One
possible way to do this is to form smaller texture maps by averaging groups of
texels.
Mipmapping provides a simple way to do this.