OpenGL/DirectX: How does Mipmapping improve performance?

Question

I understand mipmapping pretty well. What I do not understand (on a hardware/driver level) is how mipmapping improves the performance of an application (at least this is oft

Answer 1

Mipmaps are useful at least for two reasons:

• visual quality - scenes looks much better in the distance, there is more blur (which is usually better looking than flickering pixels). Additionally Anisotropic filtering can be used that improves visual quality a lot.
• performance: since for distant objects we can use smaller texture the whole operation should be faster: sometimes the whole mip can be placed in the texture cache. It is called cache coherency.
  • great discussion from arcsynthesis about performance
• in general mipmaps need only 33% more memory so it is quite low cost for having better quality and a potential performance gain. Note that real performance improvement should be measured for particular scene structure.

see info here: http://www.tomshardware.com/reviews/ati,819-2.html