A technique used by 3D rendering engines
for First Person Shooter
type games. This technique is designed to prevent pixel
granularity when approaching a texture. The texture
is actually rendered several times at differing resolutions
As the viewpoint approaches the texture, the texture is scaled up, until a certain threshold, when the rendering engine loads the next higher resolution texture.
The popular computer game DooM did not use mip maps, so when the player approached a wall the texture used became very blocky and pixellated. Newer games of this genre tend to use mip maps and so textures do not become grainy, even at point blank range. Most modern rendering engines will automatically generate mip maps if they are not pre-supplied by the data files of the game.