Yeti supports the Alembic for Grooms Specification created by Epic to provide a common means of exporting hair and fur to their Unreal engine from DCC's using the industry standard Alembic file format.
The easiest way to do use this is to select the groom you want to export and use the Export Unreal Abc Yeti menu item.
Alternatively you can use the script command
pgYetiCommand -exportUnrealAbc [filename (string)]
In either case the current Display density will be used to evaluate the graph so the exported asset will match what is visible in your viewport.
When exported Yeti will map attributes defined in the graph to those in the Groom spec based on this table below.
|Yeti Attribute Name||Yeti Data Type||Groom Spec Attribute Name|
|Width||vertex float||Alembic's default curve width data|
|s and t||uniform float||groom_root_uv|
|groom_guide||uniform float (should be set to 1 or 0 as it's converted into a boolean)||groom_guide|