title: Cant draw hills on terrain in Unity 5.3.2
body: <p>Im new to unity so please ignore my mistakes :p</p>
  
  <p>My problem is that, I placed a terrain in my scene, made the environment as i wanted, and now i want to make some changes in it, like draw some more hills, put grass and trees,</p>
  
  <p>But now when I select "Raise/ Lower" tool from the inspector to draw hills on my terrain....nothing happens....However when I place a new terrain everything works fine :( I made that environment last day, now when I tried to make changes by doing the same as I did yesterday, but its not working....:/ Am i doing something wrong? please tell me</p>