Official SDK - All Bright
Right, so this is kind of disappointing. I got the official SDK and suddenly I can't compile any of my maps without letting the compiler open my map - I can't leave Portal 2 open and let the map just start loading.
Not only that, but everytime let the editor load the game, everything, even the official maps (even campaign mode from the main menu) is set to -allbright and nothing I do can change or fix it.
Is there any way or command to add to the compiler that fixes this? I'd rather not have to manually load my map everytime I want to run them.
Better yet, is there a way to 'fix' it so that I can keep Portal 2 open, hit compile, and wait in Portal 2 for my map to start loading, like I did in the Alien Swarm SDK? 
Oh and the reason I keep Portal 2 open, besides faster loading, is because otherwise the viewports in Hammer break like 2/3 of the time when Portal 2 opens or closes, even when it's in Windowed mode. So yeah, I'll be submitting it as bugs, but in the meantime... am I doing anything wrong?
I don't have a solution for brightness you're experiencing as I'm not having the problem.
As far as compiling goes. just uncheck the $game.exe and you'll be able to work like before
Has anyone tested if -hijack still works? It would be able to not only compile the map, but reload the map if it is running in-game already.
If you guys are noticing what you might think are bugs, then I would really suggest you join the official Portal 2 Mappers mailing list and report them there. The new SDK is in "beta" so the only way to help is to report it to Valve.
Please do not Private Message me for assistance. Post a thread if you have questions or concerns.
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have you tried mat_fullbright 0 in console ?
if you have no lights in your map it sets automatic mat_fullbright 1