Root bone as pelvis vs ground?

Question

In many rigs I have seen, the root bone is located in the pelvic area. However, where walk cycles are concerned I have also seen tutorials where there is a ground bone (or whatever you want to call it) that is hierarchically above the pelvic bone, but of course physically located at the lowest part of the armature - usually Z:0. This bone serves to position the entire character while walking, jumping, etc. Today I found myself asking: couldn't that just be an Empty instead?

What are some possible advantages or disadvantages of having a ground bone vs using an Empty (as a Parent of the Armature object) to control the character's position?

Answer 1

Having the ground bone as part of the same armature makes it much easier to animate as you can just stay in pose mode for the one armature the whole time. Furthermore actions are designed to be applied to single objects so it helps there as well.

The only reason why you might not have a root ground bone is if you are planning on exporting the rig to another piece of software with different expectations (e.g. matching a default skeleton in a game engine that has the root at the pelvis). In this case parenting to an empty isn't going to be that much help either though as the program likely won't know what to do with that either.