Mannequin animation retargeting

How to retarget animations from Mannequin to Ready Player Me avatars.

Ready Player Me full-body avatar skeleton is not compatible with the Mannequin skeleton. To apply Mannequin animations to the Ready Player Me avatars, the animations need to be retargeted using an IK retargeter.

1. Find in a file explorer: [PROJECT_NAME]/Plugins/ReadyPlayerMe/Resources/RPM_Avatar_Rigs.zip.

2. Unpack the Zip file to a folder. The archive contains a FootIK control rig, an IK rig for the RPM FullBody avatar, and two IK retargeters, one for UE4 Mannequin and another for UE5 Manny. These files are delivered inside a Zip file because the plugin is also compatible with UE4.27.
3. Add the control rig and the IK rig directly to the Content folder of your project.

4. IK retargeter for UE5 Manny depends on IK_Mannequin IK rig. Make sure that the file Content > Characters > Mannequins > Rigs > IK_Mannequin exists. Add the IK retargeter directly to the Content folder of your project. Afterward, open the IK retargeter In Unreal Engine and set the Retarget target to RPM_Mixamo_FullBody.
5. If you need to retarget animations from UE4 Mannequin, the same can be done for the IK retargeter for UE4 Mannequin, make sure that the file Content > Characters > Mannequin_UE4 > Rigs > IK_UE4Mannequin exists.

6. (Optional) Depending on the use cases we might need to adjust the hands or the feet of the avatar so they would be in the same position. To enable this functionality and adjust the IK goals, select the chains that you need (LeftArm, RightArm, LeftLeg, RightLeg) and change the Blend to Source value to 1. This functionality might be very useful when retargeting animations for the FPS game, where the gun needs to be positioned correctly in the hands of the avatar.
7. You can move those files to other folders from the UnrealEngine's Content Browser afterward.

8. If you retarget an Animation Blueprint it will retarget and create a copy of every animation and blendspaces that is used in the blueprint as well as create a new Animation Blueprint. Right-click on the ABP_Manny Retarget Animation Assets > Duplicate and Retarget Animation Blueprint, This will open the retargeting window.

9. Select the newly added IK Retargeter, set the folder for the retargeted animations, and click Retarge. This will create an animation blueprint along with all of the retargeted animations.

   
10. Once the process is complete we should end up with animations and/or animation blueprints that work with our Ready Player Me avatar.

11. The default third-person template comes with the CR_BasicFootIK Control Rig, which uses bones specific to the Mannequin skeleton. We need to change the control rig in the animation blueprint to use CR_RPM_BasicFootIK in order for it to work with our skeleton.

12. Make sure to assign the Override Physical Asset in the SkeletalMeshComponent of the character blueprint. You might encounter issues with shadows otherwise.