Help with rotation problem of parent/child actors


A rotation related problem/question.
I’m sure this could be fundamentally simple but I obviously lack the needed knowledge to solve it.
Hope someone could help me understand.

My goal is to know: how to rotate a child actor by just rotating its parent so that the child actor will be rotated to match the parent actor’s current rotation.
I can do it if its only one axis, but if the child actor has rotation offset on 2 or 3 axis, I could not find a way to calculate the right value to feed to the parent actor.
I have tried nodes like CombineRotation, DeltaRotation, etc, but have no luck.

Here is an example to illustrate what I mean:

Here I have 2 chairs with the same location and rotation,
They are paired so the yellow chair is the parent and the blue chair is the child.

Scenario 1
First: the child blue chair is rotated on one axis: Z = 90

I can apply the negative value of the rotation on the yellow parent chair: Z = -90
So that the blue child chair is ‘reset’ back to the old position, as I needed.

Scenario 2
The blue child chair is rotated on 2 axis: X = 60, Z = 50

Simply using the negative value from the child chair’s rotation does not work, as shown below
How do I calculate the values to put on the parent chair?

I hope I made myself clear.
If not, please let me know.

Thanks for your time and help.

I’m not very good with vectors, there is no doubt a fancy way of doing this in BP. For the time begin, it works fine if you swap the parenting and rotate child back to zero :slight_smile:

This is it in blueprints, it’s to do with composing local and world transforms, with an invert transform thrown in for good measure:

Thanks a lot.
This works for me beautifully.