A mipmap is a sequence of textures, each of which is a progressively lower resolution, prefiltered representation of the same image. Mipmapping is a computationally low-cost way of improving the quality of rendered textures. Each prefiltered image, or level, in the mipmap is a power of two smaller than the previous level.
You can use mipmaps when texture-filtering by specifying the appropriate filter mode in the D3DTEXTUREFILTER enumerated type. To find out what kinds of mipmapping support are provided by a device, use the flags specified in the dwTextureFilterCaps member of the D3DPRIMCAPS structure.
For more information about how to use DirectDraw to create mipmaps, see Mipmaps.