We have a problem using additive animations. The resulting rotations (especially visible in the upper arm) are wrong.
To identify the problem I created some very simple additive animations of single bones (with the character in T-pose). What we observed is this:
In the additive animation the upper arm is rotated around its local x-axis (in MotionBuilder).
What we want and expect when the additive animation is played on the idle is this, the upper arm rotating around its local x-axis:
But what we get in Unreal instead is this:
It looks as if not the local animation of the arm joint is added but the global rotation from the animation from the T-pose (compare picture above to first 2 pictures).
In Unreal the additive animation settings are set to base pose and local space.
Thanks for any help!