Rigify Rig: What's moving the chest bone? I was looking at the Rigify rig for how it is solving some problems as I was implementing my own IK rig. But I am not able understand this:

Instance a Human Meta-rig, and generate the Rigify rig (no need for having a character). Hide all layers except the torso. Now, when you rotate the hips or the spine bone, the chest bone moves in world space (but not in local space). The chest bone is a child of the torso bone (which has the cube shape), whose transform doesn't change on rotation of spine or hips bone. Both the chest bone and torso bones also don't have any bone constraints.

What's causing the world space location of chest bone to change on rotation of hips or spine bone?

P.S. The reason I want to understand this is: I have a similar torso design, and I want that the chest bone in my rig also move the same way, so that it remains attached to the body (visually). But in my case, the chest bone actually remains static in world space right now, on rotation of hips/spine bones.

Thanks in advance!
The answer is so much simpler than what I was thinking: You can set "At:" field in the custom shape options for a bones. The bone itself doesn't follow the body, just the custom shape does.