Hi guys!
I found out this amazing tool (http://jpbouza.com.ar/wp/blenrig/) that you can use to automatically rig your Sim in Blender 2.63. I played around it for a little while and I honestly have to tell that it really does its work properly. It would make the Sims 3 animations world really simple IMHO.
Is there any way to implement a similar armature in the package? I mean, it's surely a particular rig, but could it work with Sims 3?

Thank you

Nope. The game is going to use the game rig, regardless of what you use to animate in Blender.

OK, thank you for the brief but really helpful answer.
I have another question... Is there a way to make the IK chains of the rig work? I mean something like when I move the feet the leg and the knee moves, too, and the same thing for the hands...
Thank you

As far as I know, there's no way to get the original IK chains into a programme to use for animation. I have been succesful in setting up my own custom IK chain, using that to animate and then transferring that to the game. This my pipeline:

1. I use AnimTool and the various Milkshape skeleton files that you can find in the Create section.
2. I export the skeleton from Milkshape to SMD.
3. Import the SMD skeleton (with the mesh) into 3DS Max.
4. Then use 3DS Max to send this model to MotionBuilder
5. Rig the existing skeleton in MotionBuilder (there are tutorials online on how to do that)
6. Animate in MotionBuilder. Motionbuilder is a very robust animation software package and is rightfully used a lot. It is a bit technical so you do have to hunker down and work yourself into its interface.
7. Send the animation from Motionbuilder to 3DS Max (3DS Max and Motionbuilder integrate in this way, by the way: you don't have to convert. There's actually just a button in each program to send your data over to the other)
8. The good thing here is that your animation is "baked" into the bones. Meaning it will work in the game without the Inverse Kinematics chain. Use 3DS Max to export your animation to SMD
9. Use Animtool to convert your SMD animation to a CLIP file.
10. Make a new package file with the new CLIP file. Edit the CLIP to remove all IK chains, or some weird bending may occur.

But I don't think that getting the original IK chains to work will ever be possible, unless a new way of converting CLIP files is found. The problem lies in the way these are converted: a key frame is placed on every frame, not just the ones that were used to animate the IK joints, this also happens in reverse (a custom animation going back into the game). This is why I always have to delete the IK chains in CLIP files to make my animations work, otherwise there's a conflict between what the IK joints want to do and what the keyframes are doing.

thank you very much for your detailed reply. I will surely try your method and see if it works for me.
thanks again!

OK...
I read something about the topic on the Intrernet but I haven't found the solution yet.
Firstly I want to specify that I don't actually use 3DS Max for my models&animations, so it would be really hard and time-wasting to learn all the commands and settings of that program.
Starting by this idea, I tried to search for a method to bake an animation to bones in Blender, that's the engine that I use.
So, I when figured out that it's possible, I thought that I could edit the Sims 3 base armature in Blender, move the bones in a simpler way with some IK Chains created by me, and then bake the animation that I made to the original bones.

I link the material that I found on the internet, just to let you know what I am working on and, in case you know something more than me about this, give me some advice that would be really accepted.

about baking animations to bones (I think this is what I need, but I don't know a lot about baking, so if you know something more tell me, please )
- How to bake an armature animation
- Various information about animation baking

about editing the armature
- Foot rigging tutorial (the first one of a series)

Thank you