there's a couple of ways that animations are saved in .x files (and probably most 3d file formats)
the first is interpolated.
this is where the model is saved with keyframes. The computer then has to workout the frames inbetween at run time to create the animation. it results in slightly more work for the PC, but a small file size.
the second is frame by frame
In this one, the position of every vertex is saved for every frame of animation. Its easier on the processor at runtime, but will probably take longer to load as the filesize is much bigger.
hope that helps
Martin
I don't have a sig, live with it.