How can I avoid this?

[AradorasXeon]

How can I avoid at big maps, that the map is being leaked? When I try to make a big map, and I just want to make a test compile to see if everything's fit I always got map leaked. How can I tell radiant, to see those "border brushes"? Anyway I use 1.5.

[MUG]

edit: edits everywhere

 

Basically, if it is possible to get from any spawn-point, or entity, to anywhere you can see the void (grey background in radiant) then your map will leak. Proper solution is to plug up any holes in your map's outer edges, quick fix is to make a big hollow box around your entire map.

 

Later part of this video may help a little, with a skybox example:

http://www.youtube.com/watch?v=_BRktFlP5sI