for Clive Barker's Undying (tm)
(c) burt, Doppiapunta 2005
Clive Barker's Undying (tm) engine can use Detail Textures to improve image quality of in-game textures. A detail texture is a very small, fine pattern which is faded in as you approach a surface, for example wood grain, or imperfections in stone. You may have seen this in almost any modern game (Unreal 2, for example): when you approach a surface, it won't get pixelized, but stays sharp with additional details appearing.
Original textures of Undying don't have detail textures set in order to get the finest performance on slow computers. That results in washed and pixelized picture when you get close to a surface.
Texture Updater updates original textures of Undying with detail textures to improve image quality and to make Undying look a bit more "modern"