A .kf file is a file which saves animation data in the Net Immerse engine. It is not used by the Zoo Tycoon 2 engine however, but there are some remaining .kf files in African Adventure. The animations in Zoo Tycoon 2 are saved as .bf files. .kf files can be created by the blender nif scripts and may be edited in Nifskope or a hex editor. For now, they are useless until we develop a conversion script.