i have been looking for 3d Bone Animation for plain C# (to be used with Sharpdx or Slimdx) but i did not find anything !!! I just find some for XNA.
Any Suggestions! Accept c++ suggestions also
I'm not sure if it goes to as low a level as you like, but seeing as Ogre has its own .animation and .skeleton formats, I think it does.
However Ogre is for C++, so what you would want to use is Mogre which is the official port of Ogre to C#. I use it, and it is great.
A slimmer solution might be Cal3D, which is an open source bone animation api, which is independent of any graphics API, unlike Ogre. It is also in C++.
Irrlicht is another alternative, it is a quite popular open source C++ graphics engine, which seems to have bone-morphing capabilities.
Lastly, I know this is not exactly what you are looking for, but Blender has some awesome animation capabilities, and is open source. There was also a recent overhaul of its animation API, so it is much cleaner and more usable. I have not done any scripting or development of Blender, but I know that its scripting is primarily in python. However, in the API Overview, it mentions that more advanced modules (which I think includes animation) is programmed using C++. (The link I provide here may not be exactly accurate, the site seems to be down right now, so I will find and post the correct link later if you are interested)
Even if you dont intend to do scripting in Blender, studying its animation techniques would certainly help you.
Good luck! :)
EDIT: Looks like this is pretty much ignored, but user Erwin Coumans mentioned in a different question that AnimKit is also a good one.