Quote - why do you use procedural instead of importing the bitmap directly onto a large terrain.

You can import a 4k x 4k 16 bit map onto a procedural terrain of any resolution* and the function will not lose any detail. This lets you preview with a 256 x 256 procedural terrain for speed, bump it up to 1024 or whatever to preview fine detail, take it back down, and then crank everything up to maximum for the final render.

*The function editor is independent of the final resolution.