its already in engine just missed the deadline so yes it will be in 4.13 for sure.
Yes docs should come.
Mobile friendliness I will leave up to individuals to decide. It might run but it will be relatively expensive.
Here are the notes I have for now:
Texture Object (T2d): The texture to use.
UVs (V2): Base UVs to use.
Tiling (S): Tiling factor.
Offset (S): The strength of the random offset. For some textures you may notice different interference patterns and so trying different values for the offset can help hide them.
Optional Heightmap (T2d): When using HeightLerp, this provides the heightmap to use.
Contrast (S): The contrast of the height lerp.
Is Normalmap (B): This must be set to true for normal maps. Checking this box performs transformation accounting for flipping and rotation of normalmap.
Enable Height Lerp (B): Whether to enable height lerp blending. Increases the quality of the blend at the cost of some instructions.
Additional Note: The heightmap texture defaults to the R channel. To change it you must make a material instance and change the Component Mask Parameter “Heightmap Channel”. This was done this way as exposing the channel as an input would require a dot product and be more expensive. This allows the channel picker to be free.