Kojima Productions developers decided to go through the expense of creating an entirely new engine, the Fox Engine, in order to avoid the limitations of licensed engines, according to an interview with KojiPro developers in the latest issue of Famitsu magazine.
"The control flow and tools we had been using were no longer a match with the times," replied Junji Tago, technical director at KojiPro. "So after Metal Gear Solid 4, we decided to design a tool from scratch that did. With commercial engines, you tend to be bound by the limits of the features already in the engine. We're looking to make something that goes one step beyond normal games, and to make that happen, it's best not to let ourselves be bound by other things as much as possible. That's why, when we thought about it, we decided to make a unique engine designed completely by ourselves."
One advantage of this approach is that Konami is able to tailor the engine to help solve the studio's problems on a deeper, more integrated level. "It's often said with most engines that it takes too much time between making something and seeing that reflected in the real game," Tago said. "The Fox Engine lets you edit things as they actually appear on screen and see the results right there. That shortens the iteration time required and changes the workflow so you can go through more trial-and-error processes to boost quality."
As CG art director Hideki Sasaki explained, the engine team is separate from the game-dev team at KojiPro, but they still work closely together in engine development. "For example, with the graphics, we have requests from [director Hideo] Kojima and the artists about the things we need to make the game's art, and the engine team implements that. If there's an engine feature we need for what we're trying to express, we have them implement it; what matters to the game always comes first. Like we said at GDC, the MGS team is basically aiming for photorealism. We're looking for realism that we didn't have before, but that in itself won't be enough to create attractive graphics. We're aiming for photorealism, but we still insert artistry when artistry is called for."
The Famitsu interview also brought up the close-up facial animation seen in the GDC footage, which Sasaki said was handled by a combination of motion and facial capture. "We debated over going for performance capture," he said, "but currently it's two separate recording processes. Going for performance capture, and combining motion and facial capture together, each has its merits and demerits. Doing it separately means that it's okay if you mess up a line during the body capture, since it'll be mixed in later anyway. With performance capture, one actor is handling the face, voice, and body movements, so he has to get everything right all at once."
There were certain practical issues behind the decision as well, including KojiPro's unique position as a AAA game developer based in Japan. "[Performance capture] would be the riskier path since it'd lead to more retakes," Sasaki noted. "We could reduce that risk by going to Hollywood or someplace else that had the environment all set up, but in that case, Kojima would have to go back and forth to and from Hollywood, which poses its own difficulties. That, along with other reasons, led us to go for motion/facial separately in the end."
One final note: Is the Fox Engine an MGS-only project or a console-only project? "We're picturing a fairly wide usage," Tago closed. "Talking strictly about the engine itself, it's certainly not beholden to MGS, and it can be used for other projects."