lighting problem: shadow on edges of brushes

I’ve been working with the displacement tool lately, and I have been making a hilly terrain, although when I added in a “light_env”, I get this:
https://dl.dropboxusercontent.com/u/74549506/2014-01-21_00003.jpg

The shadows are in the same places as the edges of the brushes. I have no idea how to fix this, can anyone help?

this usually happens when you’ve made every face of the brush you’re working on a displacement.

You should open the face edit tool after selecting each brush, de-select the top faces while holding ctrl, then go to the displacement tab and click “Destroy”. this will get rid of the unnecessary displacements.
Then you should re-select your remaining faces and click “Sew”, this makes the displacements seamless if they are lined up correctly.

Thanks, I’ve used the displacement tool before, but this is my first time using it with lighting.