Sketchup - rough/soft edge on (flat) surface


i want to have a sort of soft or rough edge around a road. i will import sketchup to lumion.
and want to create something like the image. road in the middle. a smooth transition to gravel and from gravel to grass.
the gravel to gras i can do that. (see image) but with the road to gravel i cant make that work…
is there a plugin or something what can do this good? i dont want a razor sharp edge

see this extra image for what i can create.
the gravel and the road has e to hard edge.
is is possible to create a smooth tranistion

You can use a texture like this one:

There is no soft transition in your picture between road and gravel. You can see a clear line. What you see is dirt on the edge of the road. You could find or make a similar texture for that.