Programs needed:
Blender 2.49b
Python 2.6.6
PyFFI 2.1.11
Blender Nif Scripts 2.5.9
Download here:
http://niftools.sourceforge.net/wiki/Blender#Installation
Autorigging doesn’t give the same result as ‘real‘ rigging unfortunately, especially the more complex animals will get some distortions. That is why it’s best to only use this technique on animals with ‘simple’ animations, like fish. The big advantage of this technique is that it is easier and quicker than ‘real’ rigging.
1.Open your animal’s model & the model you want to rig it to in Blender.
2.Remove the LODs of the model you want to rig your model to. (Not all models have LODs, so you don’t always have to do this step)
3.Make sure your model fits the other model as best as possible by scaling and/or rotating it. You can use the wireframe mode to make this easier. Don’t forget to apply the new scale (Ctrl+A).
4.Select your model and the bones you want to rig it to and press Ctrl +P. Then select: Armature – Don’t create groups
5. Now select your model and the original model and press: Object – Scripts – Bone Weight Copy.
6.Choose Quality 1 or 2 (2 is better) and press Ok. Now wait till Blender is finished.
7.Now you can delete the ‘original’ model.
8.Now export your model to .nif format. (Select your model and the bones and press File – Export – NetImmerse/Gamebryo)
9.Now you only have to nifcode the model in Nifskope and you’re done !
If you don't understand this tutorial you can watch this video: