Paint a dirt path on terrain at runtime?

Hi there,

I want to be able to place a rectangle on any point of Unity terrain and have it so the detail grass under that object is removed and then have it so it paints the terrain under that object with a dirt texture.

The reason for t$$anonymous$$s is that when a building is placed I want to paint a dirt path out the front of it.

Is t$$anonymous$$s possible?

Thanks!