Thanks for the kind words. The get texture from surface features depends on you having a surface node attached to your generator. The map uses the surface's UVWs to place the texture and the segments will take a single colour from the pixel that sits below it on the surface. To determine that location, RailClone uses the centre of the bounding box for the transformed segment.
Regarding the built-in macros. I have plans to release several mini tutorial explaining them in the future, as well as how to build your own.
I hope that helps to clear things up, please let me know if you have any further questions.