Yes, I know what niflib is, but thank you for the overview. It's not really what I want but it may or may not be the closest I can get.
Personally, I am trying to extract mesh data from skyrim armor .nif files. I want complete triangles and vertices for a NiTriShape branch -- including bone weights for the vertices. So far, I've not gotten very far because of my limited knowledge of the internals of the niftools and because of the early stage of development of skyrim support in nif tools, and because compilation instructions are a bit sketchy, and because of lack of time on my part -- not even an hour a day on average -- and because my dev environments have some "bad things" about them (like: I had msysgit path in system path, seems to be bad for qt build environment -- though not in a way that generates any errors or warnings, just problems using the builds after they have been compiled).
At one point, I was hoping that I could have a text file export/import for the meshes, and was pointed at the maya obj export/import facility. But that is not complete enough for my purposes. (For example, it does not include the "vertex weights" that might go in a .skin.txt file: http://graphics.cs.cmu.edu/projects/sma/textData/
-- and I recognize that skyrim uses keyframe and not eigenskin animations). [And, in case this matters: I will also be wanting to update the mesh -- changing the number of vertices, the number of triangles and some of the values within the mesh, and I am going to want to import the changed mesh.]
One of my struggles is that the architecture of niftools very much focusses on the object structure implied by the nif files. I do not want that. What I want is nearly relational in structure: The texture paths; the vertice coordinates, normals, tangents, binormals, uv coordinates, bone weights, and the triangles. As far as I am concerned, or my current belief is: it's all simple blocks of data and I just need to understand how their locations and sizes are encoded.
So, anyways, when someone has something working, I like trying to find out specifically what they used, so I can try that myself and see if I can get working sources for something that deals with skyrim .nif files. (I need working sources because the underlying file structure is only documented in source code.)