This reminds me when i worked on an open world game ~12 years ago. I implemented spline-based "stripes" (think long decals), mainly to be used for roads (though

This reminds me when i worked on an open world game ~12 years ago. I implemented spline-based "stripes" (think long decals), mainly to be used for roads (though could also be used for smaller things like blood trails) and i added a button in the editor to align the terrain with the stripe with a configurable falloff so that it transitions smoothly from the stripe to the surrounding terrain - and optionally you could use a (grayscale) texture to modulate the falloff so that the transition isn't completely smooth. Next thing i knew, the environment artists had started using stripes to sculpt the terrain :-P