SpeedTree is a procedural generation application designed to create foliage for digital applications. Unreal Engine supports the SpeedTree .st9 format, as well as the legacy .st format. For more information on using SpeedTree with Unreal Engine, see the SpeedTree documentation.
Unreal Engine imports your SpeedTree content using a set of Material and Material Functions that are found in the Engine/Plugins/SpeedTree Importer Content folder.