The MH Groom Exporter exports groom curves and attributes to an Alembic file specifically formatted for Unreal Engine. It allows for exporting individual groom assets only.
The Source Mode can be either Groom Workspace or SOP Geometry. By default, both guides and strands are exported, with the option to export guides only or strands only.
The Groups tab allows you to export all strands and guides as one unified group, or split them into multiple groups, enabling detailed control over attributes such as width, color, and simulation in Unreal Engine.
Users can export various attributes from the groom, all designed to be MetaHuman-compatible. Additional attributes beyond the defaults can be included by enabling them in the export node. This provides flexibility to export custom data such as color, ambient occlusion, or other user-defined attributes when needed. These exported attributes follow Unreal Engine conventions to ensure compatibility during import.
Unless it is defined otherwise exported grooms will be Y up and the scale will be adjusted to be Unreal Engine compatible.
Alembic Schema for Grooms
The Groom Exporter will export strand-based grooms created using Houdini in an Alembic file compatible with Unreal Engine. To standardize the import process into Unreal Engine, an informal schema for hair data was implemented.
If an Alembic file contains curves but does not follow this schema, the groom will still import into Unreal Engine — but without any custom attributes.
When this schema is followed, Unreal Engine can interpret and apply key attributes such as width and color, along with guide attributes used for simulating interpolated hairs. Support for multiple hair groups in a single Alembic file is handled via the groom_group_id attribute. The rootUV attribute is also supported and retrieves the UV coordinates of the underlying surface (such as skin), enabling spatial variation across the groom based on its attachment area.
By default, the exported attributes include groom_group_id, which defines group segmentation. If not explicitly set, only one group will be used. The groom_width attribute is exported if width data is present. If guide curves are selected, they will be tagged with the groom_guides attribute. The groom_rootUV attribute is automatically included to support spatial variation across the underlying mesh surface.
More information can be found in the Alembic for Grooms Specifications.