Carmack builds the graphics 'engines' that make id's games go. The ideal engine of a 3-D game is an intricate and elegant construct of code that allows players to speed through solidly built virtual worlds. The engine allows every picture on a monitor to be drawn there quickly enough to convince hand and eye that it is instantaneous. . . . Carmack has put Doom behind him. Long before the game was finished, frustrated by its engineÕs limitations, he started building another from scratch. . . . something entirely new, whose engine lets id raise the stakes for 3-D world-building one more time.
(Marc Laidlaw, "The Egos at Id, "Wired August 1996, 124)