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Call of Duty 4: Modern Warfare
Call of Duty 4: Modern Warfare is a first-person shooter video game, developed by Infinity Ward and published by Activision for the Xbox 360, PlayStation 3 and Wii video game consoles and the Microsoft Windows and Mac OS X operating systems. The game was released in North America, Australia, and Europe in November 2007 for video game consoles and Windows, was released for the Mac in September 2008 and was released for the Wii in November 2009, given the name Reflex Edition. It is the fourth installment in the Call of Duty video game series (excluding expansion packs), and is followed by a direct sequel, Call of Duty: Modern Warfare 2. The game breaks away from the World War II setting of previous games in the series and is instead set in modern times. Call of Duty 4 was in development for two years, and it uses a proprietary game engine.
The first thing you will have to do is download The Official Call of Duty 4 Mod Tools, Here.
Radiant is a program in which you will be doing all of your map work in.
The mod tools come with Radiant and all the other tools, needed for Mapping and Modding.
Here, is the Radiant Mapping Guidelines.