How can the transformation of the upper body spine skeleton affect the ik_hand_gun skeleton?

Development Character & Animation
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1

Here is the character skeleton:

ue1
ue11920×1104 256 KB

Now I am implementing QE-leaning functionality in ABP like this, just transform some spine bones:

image
image1318×460 95.2 KB

However, the ik_hand_gun bone does NOT transform with the upperbody, as it’s not under the main hierarchy of the Spine Bone. If I attach a Weapon in the ik_hand_gun bone, it will not rotate with the upperbody:

image
image1638×938 193 KB

The ik_hand_gun only moves when playing animation assets(as it is used to create animation sequences in Blender). It will not be changed by some behaviors in ABP. How can I solve this?:sob:

2

Either include the ik_hand_gun in Layered Blend per Bone for the upperbody split if lean is enabled, copy rotation/translation from the hand_r joint to the ik_hand_gun joint.
Frankly it’ll be better to handle the leaning using an animation that will carry the needed joints.