Jayna Pavlin’s Very Derivative Clavicle Set Up

Create null for the Clavicle

Create a curve controller for the clavicle

Freeze Transformations on it after placing it

Parent it to the null

Unparent your arm rig from the rest of your character heirarchy.

Create a group above your arm rig (not including the clavicle) and move its pivot to the shoulder, call it something like L_ARM_RIG_ALL. 

Note: this will not be under a null, but should instead be the parent of the null over your upper arm controller.ull and freeze transformations again

Create a locator and name it L_CLAVICLE_DUMMY

Move the locator to the clavicle joint L_Clavicle_Dummy

Parent the L_ARM_RIG_ALL group under the L_Clavicle_Dummy

Select the clavicle controller and then the clavicle joint and Constrain>Parent Constrain

Select the clavicle joint and then the Clavicle Dummy and Constrain>Parent Constrain (maintain offset)

Select the L_ARM_RIG_ALL group and the L_Clavicle_Dummy and in hypershade select the graph input/output nodes

Select a mult/divide node from general utilities (left side of the hypershade)

Select rotation out of the L_Clavicle_Dummy to input1 of the mult/divide node

Select the output of the mult/divide node into the rotation of the L_ARM_RIG_ALL

On the L_Arm_Controller (or equivalent) create an attribute called Inherits_Rotate_Off and set it to go from 0 to 10 with the default being 0

Create a set driven key with that L_Arm_Controller’s Inherits_Rotate_Off attribute driving the multiply/divide nodes Input 2X, 2Y, and 2Z attributes. When Inherit_Rotates off is at 0, the multiply divide notes Inputs should be set to 1, when Inherits_Rotate is at 10, it should be at -1

Parent the L_Clavicle_Dummy to your top spine controller not under the L_Clavicle_cntrl

if it spins out, cntrl-Z to undo, then group it under a group called L_CLavicle_Group

create a null; select the top spine join and then the null and do a parent-constraint with maintain offset left unchecked

delete the constraint

parent the L_Clavicle_Group under the null

select the null then shift select the spine controller and parent (P)

then select the null of the clavicle controller and shift select the spine controller and hit P to parent it into the heirarchy. it is part of the spine heirarchy and not at the top of the arm heirarchy of null/controllers.