This will be a 3-part tutorial series on making objects react to other objects. This tutorial will be covering how to make a full body IK rig react with rigid body dynamics.
If you already have a rig, you can skip this part.
Setting Up The Collision Objects
In most cases you'll have skinned geometry connected to the joints. This doesn't affect the work flow in our case because we'll be using separate collision objects.
Step three - Now, use different primitives and sizes of primitives to create the rest of the collision objects (we used one box to make the hands; normally you'd want to make a bunch of small boxes to make the hand in more detail).
Rigging The collision Objects
We;re not going to smooth bind or rigid bind the collision objects to the skeleton. This would make then ineffective in a rigid body simulation. We're going to parent each object to an appropriate joint.
Step two - Do the same with all the joints and collision objects, only remember that the joint that you're creating a parent of your collision object needs to be the nearest joint, not the bone (the bone is the object that spans between two joints).
Now when you move your skeleton, all your collision objects should follow your skeleton.
Note On Animation
I've created a simple animation of the character walking and hitting a wall of boxes (yes, I know this animation is bad, but since this isn't an animation tutorial, I don't think it's required that it looks good).
Creating The Rigid Bodies
To follow this section exactly, you'll need to download this scene file. This file contains a wall of boxes, a floor, and the animated rig. If you don't understand rigid bodies, you should read this tutorial. Link:
Step one - Select the box wall and, on the dynamics menu set, got to fields>gravity. This will automatically turn these boxes into active rigid bodies and assign a gravity field to them.
Now play your animation and you should see the rig walk into the boxes and the boxes will be pushed aside.