Root Motion is an important part of a retargeting workflow. Unfortunately it has not been working within UEFN for some time now.
As shown in the video above the root motion scale translation for two UE5 skeletons is set to 1.0 by default. For the motion to play correctly with the root bone, the scale must be adjusted in the retargeter to .01
This allows the animation to retarget correctly to the target mesh. However, when used within a level, this shrinks the target mesh’s size to exactly .01 of what it should be. This requires turning the mesh scale up to 100 to compensate, making staging meshes for animation very difficult.
In Unreal Engine 5 this same process works without issue. Let me know what else I can do to help.
Hello, thanks for reaching out about this retargeting issue.
Erratic root motion scale can be caused when the bone considered as the “root” of the body (this is separate from the root of the skeleton) is on or near the floor.
The solution is to set the retarget root to the Pelvis/Hips bone. And use a Pin Bone Op in the post settings to generate the motion for the skeleton root (“Root” bone).
Please let me know if that helps.
EDIT: Use a Root Motion Generator Op, not a Pin Bone. You could use Pin Bone to pin the root to the other root bone, but the RMG op gives you more control.
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Thank you Kiaran for this response. I feel that I am getting closer to understanding this.
The root bone is set to pelvis in the IK 
I have set up a “Root Motion Generator” in the “Post Settings”
The scale translation in “root settings” is set to (1.0)
I am happy to say that this produces positive results within the retargeter.
But in the sequencer the target is still exactly 100x smaller than it should be.
In your previous message, you suggested a “Pin Bone” in the Post Op settings. How would I set this up and what settings do you recommend? I have tried every combination I can think of between the pelvis and the root without result.
Thank you again for you help.
@SirDustyDirks Glad to see your root motion is sorted out. You were correct to use the Root Motion Generator. The Pin Bone Op is used to pin auxiliary bones (like pinning IK bones to hands etc). You caught me before my morning coffee haha.
As for the scale issue in sequencer, I’m not really sure what is going on there. Can you verify that the scaling disappears when not running a retarget? It may be due to something else…
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@KiaranRitchie Thank you again,
Everything is looking great in the retargeter. You can see my settings in this video.
But when I use it within the sequencer everything is off the scale, almost as if the post settings are not applying to the target once I export the animation.
In the video above the courser, the mesh appears when the animation starts playing. When the animation completes the mesh resumes its normal scale and positioning.
My email is seth@moistymedia.com if you are willing to connect on this. I can demonstrate this issue in detial. Thank you!
Hello! Replying here as this issue persists but I have made a discovery. The issue comes from the global root bone.
In the third video below you can see that when I convert the animation to FK the bone scale is dropping to .01 instead of 1.0 which is the default. I am confused as to why the retargeter is doing this on its own as this root bone is not a mapped chain in the IK rig.
Please let me know if this sheds any light on the issue. @KiaranRitchie Thank you