Exporting animations from Blender to DirectX

It's been a while since my last post... Owh Gooood! The most time and energy consuming thing is behind me. Skeletal animations has been written and I'm really happy about it. In fact, I was swearing at them all the week, the more technologies you use - the more potential bugs you get. What a discovery!

Let me share a few critical problems I got on my way. Maybe it'll save someone's time in the future ;)
It's not a tutorial or step by step instruction, only hints.

1. Exporting skeletal animation from Blender (v2.65) to a .x file
   
   • Only active ArmatureAction strip is exported, I was trying with NlaTrack but failed
   • Remember to triangulate the mesh
   • Keyframes on frames <=0 aren't exported
   • Bones have to be in rest pose before running the exporter (but not in Rest Position from Skeleton tab in Object Data panel, I prefer to make a special "rest keyframe" in frame 0)
   • You need to select armature and object first, then launch the .x exporter
   • My exporter options checked:
     
     • System: Right-Handed (my Assimp loader is configured to automatically change coordinated to Left-Handed)
     • Apply Modifiers
     • Export Textures
     • Export Armatures
     • Animations: Keyframes Only (I guess you know why)
     • Export: Selected Objects


2. Importing a .x file with Assimp library
   Assimp interface is very neat, so there probably won't be any problems with it. The main I had, was with this function:
   Despite of a fabulous name - it just converts Assimp matrix to XNA matrix. They're both structures with 16 floats in them, and XMFLOAT4X4 has a constructor that enables to build it from a float pointer.
   Tracking this error was a really funny thing, you know where was the problem? The returned XMFLOAT4X4 matrix was transposed... Here's the fix:
   
   
3. Some code issues:
   
   • Watch out when you want to have a structure like a list of keyframes containing offsets of every bone in current pose. When you're importing, you have a list of channels (corresponding to bones) containing offsets for every frame. It's easy to write some dirty code here.
   • Take a special care for quaternions. Sometimes they're stored as (x, y, z, w) and sometimes as (w, x, y, z)
   • IMHO pointers are much better than lists when managing a bone and animation structure
   • When stuck and don't know what to do, start small. Make a super simple animation with a 3 bones and 6 vertices. Debug all transformations and properties, you'll figure out what happens for sure :)