The proper math Murphy didn’t mention would be done using the Object Bounds.
You have to fuss with it because I dont remeber the exact formulae, but something like bounds x 2 divided the world position.
The result you want is that if you take a texture (any texture, any size), it is accurately stretched across the whole landscape actor you are currently dealing with.
The line trace process is likely still used to determine which landscape (or mesh) you are interacting with, so that coordinates/UV sizes can be adjusted for the render target you are using to work.
Actually you are in extra luck again. I found a screencap of the formulae.
Go play the lottery or something…
Obj position - obj bound defines one corner.
You subtract that from wpo so you get the starting point, then you count up the bounds to define the area of interest…