So recently I have been working on inverse kinematics as part of my game development project. The motivation is mainly because I have found it very difficult to export animation from blender to my projects. Blender pose bones are in some very weird transformation spaces plus the xyz coordinate system adds ta new level of frustration. I have tried countless times to force blender to export the animation to local space of each joint using parent-child inverse matrix but it never seems to work.
Well, enough with that nonsense. I have written an excellent IK solver system and post a tutorial of on my website. Take a look. Comments are greatly appreciated.