Alex St. John is a former Microsoft employee who started the development of DirectX and by some is considered the father of gaming on Windows. Notably, his work in this direction was heavily influenced by Doom which by his account was a "religious phenomenon" at the Microsoft campus.
In 1995, Microsoft's focus was primarily "multimedia" -- essentially meaning video and educational material. Alex St. John however came to the insight "that the future of multimedia wasn't Encarta, it was DOOM"  and became "one of the leaders of the effort to make the company a player in gaming graphics."  A small group of developers, including St. John, subsequently developed WinG, "a video API that could run DOOM almost as fast under Windows as it did in DOS". WinG evolved into DirectX, which was used for the company's port of Doom, Doom95.
St. John left Microsoft to found WildTangent, and has notably also been involved in public debates about graphics technology with John Carmack.