Encouraged by the amazing progress of the project I will take a risk and ask the same question for the third time (it was, unfortunately, ignored twice in the past on OpenMW topics. No offensive, I understand: there could be reasons for that).
MW/OpenMW PC/NPC/creatures Animation System.
It is not a secrete that MW animation system (data storage (nifs/kfs), AI, animation related scripting functions, collision detection/propagation, etc.) is outdated, very rigid (several serious hardcoded limitations), and primitive even for the moment of the game release. Moreover, there are several serious bugs (e.g. not working for NPCs PlayGroup/LoopGroup functions).
Animation system is a substantial component of a video game. Hence, without significant revision/improvement of it in OpenMW the project IMHO is doomed to remain a pure eye candy (competing with MGE).
I am going to talk neither about fancy things like Havok/PhysX, bone LODs, lip-sync, flex, morpheme, nor about animation related scripting aspects (on this stage of project development). So, let's be realistic: OpenMW is not that opened ? it uses exclusively MW specific nif/kf format (4.0.0.2, very old version) and has Ogre3D as a base (expertise and time of project developers are also not infinite). Moreover, I would like not to post walls of text. I am not a game programmer or artist-animator but I know some MW animation technical details and have access to animation software. To be short, main limitations of MW PC/NPC/creatures animation system (as promised no animation scripting, AI, etc. questions/requests) from my point of view are:
1. As you know MW game engine takes animation data from kf files (x.nif contains corresponding skeleton structure, .the third animation nif is used only actually only in the TESCS) that contain text keys/note tracks (NiTextKeyExtraData) with sequences names (e.g. Idle7, WalkForward, Death2, etc.). These names are hardcoded and their number (206) is limited: there is no way for instance to add totally new combat animation or more that seven idle animations (Idle is reserved for transitions, Idle2 is not supported). This limitation is MW specific, NetImmerse v.4.1 (MW is based on this NDL game engine) does not have it. It would be great to overcome this limitation in the frame of OpenMW.
2. All MW animation sequences should be stored in one huge file: it is possible to "attach" only ONE animation file to a given NPC (PC third person is an NPC with ID "Player") or creature. This is a NetImmerse recommendation that was removed in later (Gamebryo, LightSpeed) engine versions: e.g. in Oblivion it is possible to add nearly unlimited number of animations that are stored in separate kfs. As a result there are zillions of custom animations for OB and only few for MW. Huge MW animations files (ca. 5000 frames) are badly handled in Max and Blender. LisTail's kit helps a lot (split/merge kf), but this excellent tool has several bugs and limitations. So, could this problem (all sequences in one file) be addressed in OpenMW?
3. Partial MW animations like NPC head rotation in the PC direction, arm animations with a torch (other carryable lights) can often corrupt main animations in the game creating totally unrealistic bending abgles. Ogre3D (like Gamebryo) has sophisticated access animations of specified bones or bones chains. How that will be implemented in OpenMW?
4. Alternative Bounding Volumes Proxy Geometry. It is relatively developed in NetImmerse v.4.1 (see MaxImmerse docs) but in MW it is reduced to one big and famous "Bounding Box" structure in animation files. The result of this are very simplified and bad collision interactions with game objects including NPCs. Hence, it is difficult to sit on a chair, to hug, to kiss?he-he. Are you going to change that?
5. Bones. For unclear reason MW PC/NPC bone names and number are hardcoded and limited (usually there are some obligatory bones with fixed names, others can be added freely). Result: no way to add extra animated bones (e.g. for hair, clothes), helper bones (additional to weapon and shield bones), twist bones (supported by NetImmerse and nicely working in MW). Are you going to break this limit?
That's enough for today (again a wall of messy text, sorry). I tried to address only features that are known to be supported in MW animation nif/kf format.
Thank you.
BTW, I have tried to summarize our knowledge about MW NPC/PC animation system here:
http://www.gamesas.com/bgsforums/index.php?showtopic=883042&hl=