Metahuman Custom Pipeline Pre-5.6 Update

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Custom MetaHuman Integration Pipeline (Without Third-Party Plugins)

This method enables integration of custom characters into the MetaHuman framework while preserving key facial and body functionalities, using only native tools in Maya and Unreal Engine.

Facial Setup Workflow

Requirements:

  • A MetaHuman scene opened via Quixel Bridge or another source.
  • The MetaHuman character must have a functional control rig with properly skinned body and face.
  • A custom character head that uses MetaHuman topology and identical vertex order.

Steps:

  1. Import Custom Face:
    • Import your custom model into the MetaHuman scene.
  2. Connect Blendshape:
    • Select your custom face.
    • Shift-select the MetaHuman face.
    • Navigate to Deform > Blend Shape in Maya to create a blendshape node.
  3. Activate Blendshape:
    • Open the Shape Editor.
    • Activate the custom-to-MetaHuman blendshape slider.
    • If the topology and vertex order match, the blend will function correctly.
  4. Resolve Hierarchy Issues (Input Order):
    • Right-click on the custom model.
    • Go to Inputs > All Inputs.
    • Drag the newly created blendshape node below the default MetaHuman blendshape node.
    • This resolves control rig dependency issues.
  5. Test Facial Controls:
    • Test any facial control via the MetaHuman Facial Control panel.
    • Controls should deform the custom mesh correctly.

Important Considerations:

  • This method provides basic functionality for human-like characters.
  • Characters with non-human proportions (e.g., large eyes or unique facial structures) will require customized or modified blendshapes.
  • It is recommended to edit existing MetaHuman blendshapes as they provide a solid base.
  • If new shapes are added (not edited), Maya will not export them due to DNA file restrictions.
  • Blendshapes in Maya are linked to the DNA file, specifically rl4Embedded > BsOutput.

Exporting Meshes

Face and Head Export:

  • Select the DHI joint chain hierarchy and head mesh.
  • Export as FBX.

Body Export:

  • Blendshape your custom body to the MetaHuman body.
  • Select the DRV joint chain and the body mesh.
  • Export as FBX.

Unreal Engine Import

  1. Import the head FBX with the DHI skeleton.
  2. Import the body FBX with the DRV skeleton.
  3. Follow the MetaPipe export tutorial for import settings.
  4. Replace the default meshes in the MetaHuman Blueprint with your custom assets.

Restrictions & Limitations

  • Blendshape Route:
    • You retain MetaHuman expressions and controls.
    • Visual appearance may partially revert to the default MetaHuman face.
    • Offers editable blendshapes but not support for newly added ones.
  • Skin Weight Route:
    • You retain full control over the custom face appearance.
    • Requires creation and manual connection of all new blendshapes to the controller.
    • Only edited default blendshapes are recognized by the MetaHuman system.

Additional Notes

  • Avoid adding new blendshapes to the existing node—only modifications to existing targets are supported for export.
  • New blendshapes must be integrated manually in Unreal's MetaHuman Controller to function.

    Add Blendshape to Custom Metahuman

    This workflow allows for direct creation and import of custom blendshapes into the MetaHuman framework, bypassing MetaPipe while maintaining control via Control Rig in Unreal Engine.

    In Maya: Creating and Exporting Custom Blendshapes

    Steps:

    1. Create Blendshape:
      • Select the face mesh.
      • Navigate to Deform > Blend Shape to create a new blendshape node and add a target shape.
    2. Modify the Shape:
      • Modify the shape without activating any facial controls.
      • You may:
        • Use Maya’s Shape Editor for direct vertex editing, or
        • Create shapes externally (e.g., in ZBrush) and import them back into Maya as targets.
    3. Attach External Shapes:
      • If using ZBrush or other DCCs:
        • Ensure the imported shape has matching topology and vertex order.
        • Attach it as a target to the existing blendshape node.
    4. Prepare for Export:
      • Select the DHI body joint chain.
      • Select the face mesh with the updated blendshape.
      • Export the mesh as FBX.

    In Unreal Engine: Importing and Hooking to Control Rig

    Import:

    • Import the FBX using MetaPipe settings, or reimport using the existing MetaHuman skeleton.
    • Confirm that the new blendshape (morph target) appears in the skeletal mesh.

    Modify the Control Rig:

    1. Locate Control Rig:
      • Navigate to MetaHuman > Common folder.
      • Locate Face_ControlBoard (Control Rig for facial controls).
      • Duplicate it to avoid modifying the original asset.
    2. Update the Control Rig:
      • Open the duplicated Control Rig asset.
      • In the Rig Hierarchy, find the Root.
      • Select your custom MetaHuman mesh under the hierarchy.

    ⚠️ Important: This step must be repeated every time you import a new blendshape to update the reference mesh.

    1. Map New Blendshape to Control:
      • Find the control you want to modify (e.g., Right Eye Blink).
      • Locate the corresponding “Set Curve Value” node.
      • Replace the curve name with your custom blendshape name.
    2. Compile and Save:
      • Compile and save the Control Rig.
      • If it fails to update or show changes, recheck the Root assignment as mentioned above.

    Known Limitation:

    • When using a custom blendshape, it fully overrides the mesh deformation, meaning it does not layer on top of skin weights.
    • This makes it less ideal for subtle corrective shapes or additive deformation workflows.

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