1. Say I have such a set of character skeleton.
2. And I have such a set of controllers.
The pinks are the FK controls for the spine,
the yellow square is for the hip(IK),
and the big blue circle is the COG.
The hierarchy of the pinks are:
the lowest circle -> the middle circle -> the top circle.
3. Now put an IK (SC solver without sticky on) from the bottom spine joint to the one above, while the IK handle is still selected, parent it to the bottom pink circle. (shift select the pink and hit "p")
4. do the same to the second joint on the spine:
put IK on, and parent it to the pink circle below it (the middle pink circle).
5. do the same to the top one, put IK on, and then parent it to the pink circle below it.
6. make the yellow square point constrain the bottom spine joint. (the square controls the joint)
7. We are almost done! Just make sure your IK legs and feet are set, and the leg roots (the ones close to the hip) parent-constrained (or parented) by the yellow square.
Now you got your hip control (the yellow square), you can move the hip without moving the shoulder or the chest. You can also rotate the hip, make it dance.
And you can still manipulate your spine FKwise.
8. Finally, put all the necessary stuff into the COG (the big blue circle), in this case they include the yellow square and the bottom pink circle. (That's it...) And this is what a COG is doing: COG controls the entire upper body, and hip control does the hip alone, and you got the FK spine.
