An issue that I've noticed while working on models for a specific game engine, is that when using exporting FBX models or BVH data comes the fact that you have two different rotations formats, with both being Euler: You have either just Lcl Rotations or a set of three rotations, Pre Rotation/ Rotation /Post Rotation (Pre/Post).
Blender takes these account when Importing FBX Models but it doesn't add the opportunity to add them back in when exporting: This is what I think has been causing many of the issues with cross-suite animations not working within games (animation done in one app, while blender user for modeling, or vice versa)
Id like to improve the FBX exporter in Blender to allow for Pre and Post rotation values would be applied to the exported model, so that it would behave like exporting in Maya. Currently It does not seem to do that.
From what I've gathered they are rotations that are in order added to each other to get the final rotation, and must have something to do with the order how rotations done in every other 3D app and Engine, except Blender (blender seems to be using quaternions behind the scene if I understand correctly).
However to do that Id need to know some math on this:
How would I go on converting Quaternions into Pre Rotation, Rotation and Post Rotation? I can implement the rest into the fbx export script for experiment.