mipmap

Mipmap is a sequence of textures used in 3D computer graphics to increase rendering efficiency and image quality. It consists of multiple prefiltered versions of a base texture, each at a lower resolution. Level 0 contains the original image; each subsequent level halves the width and height, continuing until a 1x1 texture remains. The entire chain is stored with the base texture and is typically generated in advance as part of texture creation.

Generation uses downsampling filters that reduce high-frequency detail to minimize aliasing. Common approaches employ box filtering or more sophisticated prefilters. The total memory required for a mipmap chain is about 4/3 of the size of the base texture, due to the geometric progression of texel counts.

In real-time rendering, texture sampling can select an appropriate mipmap level based on the projected size of the texture on screen, or interpolate between levels (trilinear filtering). This reduces aliasing in minification and improves cache performance, because smaller mipmap levels are more likely to fit in texture caches. Anisotropic filtering may be used in conjunction with mipmaps to preserve detail at oblique viewing angles, at additional cost.

The concept dates to the 1980s, and the term mipmap was coined by Lance Williams. Hardware and graphics APIs routinely support mipmapping as a standard feature, and it is widely used in modern game engines and visualization tools.