I am working with the free Assetsville Town package from the market place and want to replace the 3rd person template character from UE5 with one of the characters from the package.
Since the characters in the pack do not use the default UE4 skeleton, the UE4 skeleton needs to be reassigned to them first. These are the steps:
Right click the desired character mesh from the pack
Select Skeleton → Assign Skeleton and Select “SK_Mannequin_Skeleton” which is the UE4 skeleton.
Confirm to add 3 facial bones.
Finally, convert the pelvis bone in the mesh from Animation to Skeleton
Now I want to get them working in the UE5 character, so I right clicked on the Animation Blueprint for Quinn and select Retarget Animation Assets → Duplicate and Retarget Animation Blueprint. Settings:
UE5 to UE4 Retargeter
Source Mesh: SKM_Quinn
Target Mesh: SK_Mannequin
Now I put a BP_ThirdPersonCharacter into the scene and possess him. I can also replace the Quinn Mesh with the UE4 Mannequin and the animation blueprint with the duplicated UE4 variant and everything works fine. However when I select the Assetsville character with the simplified skeleton, the IK no longer works correctly and the feet are stuck and not moving.
I noticed that in the duplicated Animation Blueprint the old UE5 Control Rig is referenced. So I duplicate the Control Rig, delete the hierarchy and reimport the hierarchy from the UE4 Mannequin skeleton:
Here I can see in the backwards solving that the IK_foot_L and IK_foot_R bones are not moving during the animation, they are stuck in place. So thats why the IK solver will always attach the feet in a fixed position.
I have basically 0 experience with IK poses, so my question is, what do I have to do so that the IK bones move together with the animated character? The strange thing is that in the UE4 Mannequin the IK bones are moving, while for the Assetsville character they are not moving. The only difference between the following two shots is the preview mesh I have selected in the top right corner. Both are using the same skeleton:
To be honest, I don’t understand why you do that…
So… do you want a character using the third-person base character?
Because of the animations? Let me download the content and see it…
Hi alberto, thanks! I just watched your tutorial on the meta human retargeting just in the hope I could learn something for my current problem I am really no expert, I worked through a number of tutorials on animation and Control Rig but I feel really lost doing it myself now
Yes I want to use the Assetsville character with the UE5 animations. Is that the wrong approach?
The animation class that you highlighted is the UE5 Animation Blueprint after converting it to the UE4 skeleton. It works with the UE4 mannequin just fine, but it does not work with the Assetsville character.
Hey thanks so much for taking the time to try this out and record the video! The video is still processing so I will wait until higher quality is available. I will continue tomorrow and write you how my progress goes!
Okay I went through the process and did everything like you in the video. I learned a lot and it was fun, too! I did not know you could retarget / refine animations in that detail. I can not thank you enough for taking the time and pushing me in the right direction!
After doing all the steps you did I was still missing the IK bones because they are not part of the original skeleton. But now that you showed me how to work with the rig manually, I tried some stuff and finally got it working.
So since I do not have the IK bones in the skeleton, I added virtual bones so that they could be used for IK. I am not sure if its a good idea to use virtual bones for IK but I found others here on the forums doing the same.
I added the virtual bones before duplicating and retargeting the Animation Blueprint and it turns out that there is a bug in 5.0.2 and virtual bones do not work correctly after retargeting, Fix ETA in 5.1:
So instead, retarget the animations with the original skeleton, then add the virtual bones for IK in the skeleton AFTER retargeting.
If the virtual bones are not correctly animating now and still stuck in place, try restarting the engine before the next step. Finally, replace the IK bone names with the virtual ones in the graph:
I think this bug may still be in the engine, and I’m still having issues with IK bones being stuck to the ground after trying the delete hierarchy in CR fix. Will do the steps over in different order and hopefully that will help
I just tried this with UE 5.3.2 and by adding the bones, fixing the skeleton, adding a IK retargeter, retargeting, and following the steps I was able to get good animations. However, the Animation Blueprint still didn’t move the feet. The animations when played individually worked, but the overall didn’t. I rebuilt the Animation Blueprint and that worked.
Thank you all for the amazing help. It would be nice if the Assetsville folks would update their stuff to work more out of the box so us noobs would have a bit easier time.
I am really no expert, I worked through a number of tutorials on animation and Control Rig but I feel really lost doing it myself now 
