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I have seen alot of maps lately like this:

http://projectmimesis.com/forum/viewtopic.php?t=1265

Like they take a map (Gemini). and I dunno how but they put stuff from signle player and other maps and make custom maps from scratch. Anyone have a breif tut or hell maybe a long tut on how to make a CUSTOM MAP!?

that is called a BSP conversion, theres a tut in the tutorial's section or look in Snave's tutorial repository

I click on the link for BSP Convesion but its nothing look:

http://files.halomods.com/viewtopic.php?t=48897

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