UE 5.8.3 MetaHuman Auto-Rigging Issue - Facial bones misplaced when fitting head mesh to custom body proportions

neowiz_namwook · October 8, 2026, 5:18pm

Summary

When running ‘Create Joints Only Rig’ after fitting a head mesh to align with custom body proportions (height/build), PCA-driven facial joints fail to follow the deformed head mesh surface, resulting in misplaced or sagging bones in the final skeletal rig.

What Type of Bug are you experiencing?

Other

Steps to Reproduce

Create a new MetaHuman Character asset in a clean UE 5.8.3 project.
Replace the body mesh with a custom body mesh using Import → From Template → Replace. (In my case, body mesh is taller than 23cm from archtype.)
Use the Mesh Fit tool to align the head mesh with the custom body mesh proportions. (Leave Isolate Head From Body disabled to prevent severe deformation of the custom body mesh.)
Run Create Joints Only Rig (Auto-Rig).

Expected Result

All facial joints (both surface joints and PCA-driven joints) should align correctly with the position and geometry of the fitted head mesh that matches the body proportions.

Observed Result

While surface joints correctly follow the modified mesh vertices, PCA-driven joints fail to receive these vertex deformation influences and take a different transform path, causing them to sag or misalign. This results in a broken facial skeleton layout in the generated rig.

Only the bones listed in Engine/Plugins/MetaHuman/MetaHumanCharacter/Content/Face/IdentityTemplate/inactive_joints.json are misaligned during mesh fit — all other facial joints follow the fitted mesh correctly.