While my map compiles (one hour and a half just for the visleafs...) I wonder... I?m going to do some outdoor map and I learned not to do very wide areas since takes aeons to compile... To do some outdoor area we must cheat the player, make him believe he?s in a wider place than he really is... We could do the area (a garden, for example) and surround it with an outer wall. And then we?ll surround this wall with a sky brush and it will make the trick... But when we shot to the sky (something very common :P) we see sparks...
And I wonder... What if I between the sky and the world I make a ticker enough to contain the sparks func_illusionary brush, texture it with sky and run the map?. The illusionary would block the sparks vision, I?m I right???. This way it would look more realistic. Maybe I?m missing something (maybe func entities can?t be textured with sky) but as I can?t try now (map still compiling... I?m growing older) I just tell you.
See if you can make it work, it would be very cool and use little rendering resources (in fact, the sky brush could be textured as null or something like that).