Software to compose separate models into an articulated model? I've inherited a system which animates a humanoid avatar by loading various models and manually calculating transformations for each one. I'm in the process of porting part of this system to Three.js, and rather than port the manual calculations across I'd prefer to pre-compose an articulated model and let the engine handle the transformations.

Is there any software which would let me import the existing models, define the bone hierarchy and the model which corresponds to each bone, and export a single articulated model in T-pose?

For what it's worth, I have access to both Windows and Linux, and if really necessary I can probably obtain access to OS X. The original models are in FBX format, but I have managed to export them to Three.js files, so I could import from either format.
Is there any software which would let me import the existing models,
  define the bone hierarchy and the model which corresponds to each
  bone, and export a single articulated model in T-pose?


I found that it is relatively easy to create articulations using Blender.
This tutorial might be helpful: Blender 3D: Noob to Pro/Bones | Wikibooks