Metahuman retargeting bugs

[DenisaXxX]

Hello,

I am attaching a video demonstrating the buggy state of the AnimBP once retargeted to the metahuman. I have added all the virtual bones prior to the retarget process. Any ideas as to why this is happening would be greatly appreciated, it has been giving me a head ache for a week now.

https://drive.google.com/file/d/1VLaGmAHe-ExqbgQxvsFE9GyFJqItzQ4O/view?usp=sharing

skeleton image
https://drive.google.com/file/d/13wTW_tL8R4dOUpWn8J-ryCyaBBhX9mxY/view?usp=sharing

Thank you

[dyanikoglu]

The foot tapping issue is a generic problem with ALS, and it's related with how you retarget, also check if your animations still have correct curve values.

[dyanikoglu]

You can get detailed information about the issue on discord server

[DenisaXxX]

Hi, The animations have correct curve values, there is a guy that did a retargeting from ALS to Metahuman video on youtube, but what he did is create all those ik bones as virtual bones and then renamed them in the actual AnimBP ALS functions to fix the issue, but those functions are hard coded in C++ so there is no way for me to fix it in blueprint with your performant ALS version.. It is driving me crazy.

[ghost]

also, make sure that in the anim instance C++ class you have renamed the ik foot variable correctly, your character will do their wiggling if you dont do this, in my experience.

[davicyyo]

I'm having the same problem, the minute of the video it describes is as follows:
https://youtu.be/t22BC_6IVyc?t=1495

There has to be some solution to modify that bone name from the virtual bones, according to the issue that has been closed (which I apologize):
#399

It is found in:
https://github.com/dyanikoglu/ALS-Community/blob/0930f7bcdd047020c5ed3b27b642c140b03146a3/Source/ALSV4_CPP/Private/Character/Animation/ALSCharacterAnimInstance.cpp#L346

[davicyyo]

Thank you very much for your contribution!

However, it has the same effect as the previous case, i.e. I have modified those values VB ik_foot_l and VB ik_foot_r in the same ways.

I just save the unreal startup file and I have no effect Will retargeting be needed again? Will this C++ code need to be compiled before opening unreal? I do not know the procedure for updating these files.

[SteveProteau]

One final part of the puzzle. Retargeting apparently breaks the constraints on the virtual bones so they are not anchored to the bones they are relative to. Here is a video on how to fix that:

https://www.youtube.com/watch?v=8HsJBHDuCU8

Note that the video is for normal ik bones. You need to swap for the virtual bones names we use for Metahuman retargeting (rename ik_* to VB ik_* and fix a few constraint bones). I have confirmed that IK now works with static retargeting! WOOT! Finally! Been a long haul getting here!

[SteveProteau]

I also had to fix ALS to use the Metahuman body when GetMesh() was called. Otherwise mantling and rotate-in-place were broken. Here is a hacky fix added to AALSBaseCharacter:

public:
// Metahuman fix for to return Body as the active skeletal Mesh
FORCEINLINE class USkeletalMeshComponent* GetMesh() const { return MetahumanBody ? MetahumanBody : Super::GetMesh(); }

protected:
UPROPERTY(BlueprintReadWrite, EditDefaultsOnly, Category = "Metahuman")
TObjectPtr MetahumanBody = nullptr;

You initialize MetahumanBody to your "Body" in your metahuman blueprint initialization. This solution works but is cringeworthy because GetMesh is not virtual so we are overriding an inline function in the base class. A better solution is to create a different accessor function to get the mesh, but that changes more ALS code and is less surgical.

Edit: An even better solution is to make "Mesh" the new "Body" and put the other body parts (face, torso, feet, legs) under that. Note that this is not what a lot of videos show but seems better than an empty mesh and works with ALS. You also have to update the master pose component to set the body parts to the Mesh as the new master bone component. Confirmed that it works.

[AchimTuran]

One final part of the puzzle. Retargeting apparently breaks the constraints on the virtual bones so they are not anchored to the bones they are relative to. Here is a video on how to fix that:

https://www.youtube.com/watch?v=8HsJBHDuCU8

Note that the video is for normal ik bones. You need to swap for the virtual bones names we use for Metahuman retargeting (rename ik_* to VB ik_* and fix a few constraint bones). I have confirmed that IK now works with static retargeting! WOOT! Finally! Been a long haul getting here!

It is possible to add ik bones to the MetaHuman skeleton as well. This should make the things way easier and also more clean. You can use the UE5.3 skeletal mesh editing tool or TTToolbox (it provides a right click function to add ik bones to skeletons like Mixamo, MetaHuman (see https://youtu.be/UJBG5WP3GfQ?si=mNLygBK80YdVWj8i).

[AchimTuran]

Also wrote down some notes here, but sadly never finished the entire guide. Maybe it helps someone.
tuatec/TTToolbox#11