This is where you have stretched vertices beyond there limits. Then compile and get lines of stretched texture or where the patch messes join.

I will show you how to get rid of this. Here’s the first Image of my terrain where you can see the light map squares don’t match cause of the manipulation of vertices.

(Make sure you have a backup of your map before trying this)

Open up radiant and load your map.

Then make sure you have "Caps Lock ON",and push and hold "Shift" + "L". your map will turn into "Light Map Mode".You will see everything in white and grey squares.

Now I turned off some filters so I can see all my terrain and structure brushes better. You can see where I've highlighted a (512x512) patch.

Then you will hit "S" for "Surface Inspector”. I found that the best way to do this is to "CAP" that piece of light map grid. Any other method seems to crash radiant when compiling. You will find that in some places even after Capping the patch the square doesn’t seem to be just right...Don't worry it will compile fine.

Then Hit "Shift+L" again to exit light map mode.

I’ve been playing with it and I have also found that if you cap all your terrain at once, it also crashes radiant in compile. So will fitting the light map texture to the patch.

What I have been doing is going in fixing a couple and then compiling. Seems to be working out good...

Hope this helps some of you’s out...