Question Additive animations on top of rig

What are the best practices for combining/adding an animation on top of rigged movement?

For example, the rig is set up to control the character's look direction with a lookAt by turning their head/neck, and you want to make the character play a headshake "no" animation whilst they're looking at the player. The lookAt rig prevents this because it overrides all movement from the animation, and turning the weight down or off would mean the character no longer looks at the player. What's the best way to 'add' this animation over the rig?

 

Surely this is a problem that's been solved before. I can't be the only one who wants combine animation with IK

 

Bump again, if anyone has insight.

 

It was indeed solved by ID software, you can check out this GDC lecture at about ~11 minutes

That said I'm not sure how does one go about implementing such feature in unity. You would have to bake reference poses for IK into scriptable object and maybe, like, have AnimatorBehaviour that would change reference poses on state enter, maybe? But general idea is to apply IK to reference pose, not actual current animation pose