I wanted to know if there was a way to create a terrain material that uses layers that contain material functions in them? I want to use a tessellation material to my landscape but whenever i add the function it makes the whole terrain turn black.
Tessellation + landscape = risky at best
I tried to do this and it crashed my game, luckily I had not saved so I reloaded editor and cleared out the tesselation from the material 
but if your only issue is that the landscape is turning black, try painting over the blackened landscape and the lighting should return
that is a known issue
work around is just paint new stuff on each landscape component until the lighting is restored
“create a terrain material that uses layers that contain material functions in them?”
I cant see any reason why this would be feasible, try out my first suggestion and see how it goes!
Rama
Thank you, But is there anyway that i could use a material function for the terrain and use it like a brush or is it something that is not possible right now in the engine? could it be added later?
isnt each layer like a brush?
and if you plug a material function into one of your layers, then you have a material function as a brush!
What you want is the layer blend node
#LandscapeCoordinates
Keep in mind, you need to plug your Landscape Coordinates into your material function, by adding a parameter in the material function for the UVs of every texture in that function
in the pic below, imagine that the texture is actually the UV input for your material function
it seems that whenever i use the material blend node it crashes my editor. I have also tried your method with the functions and it seems that it still is not working, i am still getting a black terrain. i want it so that i can create a material with a normal and more complex networks for more detail on the terrain instead of the texture.
Landscape Layer Blend node causes the editor to crash. This is a known issue and i have reported it here and Epic is looking into it. So at the moment you must use Layer Weight node.
Satheesh is correct about this crash error. We are aware of it and it has since been resolved internally. The fix will be implemented in a future release of Rocket.
Cheers!
Alexander