Question tutorial on terrain tool custom shaders?

I have searched several times for this over previous months, but always came up short. I was wondering if there was a way to use custom shaders with terrain tools. Right now, using terrain tools, you can paint the textures as layers over the terrain. What I would like to do is be able to do the same, but with shaders, using the splatmap to determine which shader is displayed.

I think terrains really need to be up to snuff for video games. We are past the days of flat terrain, so painting textures only gets you so far, you know? To be able to utilize tessellation within a shader, and all the other things you can do with shaders, would allow terrains to go so much further.

If anyone can point me in the right direction, if a tutorial exists, I would appreciate it. Thanks