Workflow with in a context.
Lets say you want to add animations to the free Mixamo characters which happens to have the same naming convention used by MotionBuilder.
Export one of the animations for a given character, I like the Goblin, to FBX and import it into MotionBuilder uncheck import animations. Since the animation is absolute the keyframes are stripped off and you have what ever character in it’s default t-pose facing in the Z direction.
Characterize the model as usual and since the Mixamo uses the required default naming convention your done with out any manual retargeting.
Do whatever animations you like.
Once done “plot” all of the animations to the skeleton.
With character selected use the characters control panel > file > save animations.
Uncheck everything and only the keyframes on the Mixamo rig is exported.
In Unreal 4 import the FBX animation and assign it to the character you exported, in my case it was the Goblin.
This is the result.
Why does the character do a flip flop?
Most time this is because there is no root node that controls what direction the character is facing as exported. You need a root nod that defines the rigs orientation and if not is pulled from the hips which usual results in the model laying on it’s back.
Bit of advice stick with MotionBuilder and work it out. Trust me it will get easier.