I have a human skeleton, I got the global position for each bone, take headNode for example, between two keyframes I got the global translation, how to get the local translation for headNode?

Thank you very much !

Have a nice day!

Or you can use quaternions.  If your not careful you can loose a axis with matrices.

Thank you very much !

Hi, thank you for your reply.
You said:
“It follows a very simple and basic rule:
ChildGlobal = ParentGlobal * ChildLocal
So ChildLocal = ParentGlobal.Inverse() * ChildGlobal.
If the node do not have a parent, which means it is already the top one in the hierarchy,
then its Global == Local.
For Translation specifically:
ChildLocalTranslation = ParentGlobal.Inverse() * ChildGlobalTranslation
Notice: ParentGlobal is the whole transform matrix, not just the translation. “

Could you tell me how to get ParentGlobal.Inverse() for position and translation ?
And how to get the local coordinate system ?