Use additive worlds NOT substractive

This was something I found out early on, using substractive mapping will shoot your light rebuild times though the fucking roof, a 2 room map with some static meshes will take minutes in substractive mode even on my quadcore, same map in additive mode takes seconds to build.

It's very easy to get used to additive, just start with a brush to stand on, add a light, then go to staticmeshes and open package UN_Sky, select one of the skydomes, add it to the middle of the world, hit space to get the rotation widget, hold down ALT to copy and rotate 180, rebuild and start adding shit to your world.
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