'FIFA 13' and the unforeseen consequences of altering connected systems

A modern sports simulation video game has so many concurrent, interrelated systems running that it's difficult to keep track of them all. Sometimes, that's even true for the developers.

A modern sports simulation video game has so many concurrent, interrelated systems running that it's difficult to keep track of them all. Sometimes, that's even true for the developers.

Soccer fans recognize the recent entries in EA Canada's FIFA series as some of the best simulations of the sport ever created. The studio tries every year to get closer to accurately replicating the beautiful game, and last year, it debuted a new physics engine in FIFA 12 to calculate collisions between players. The Player Impact Engine considers a not-insignificant number of inputs — momentum, direction, and player size and strength among them — to figure out how footballers should interact when they come into contact with each other.

FIFA 12's physics engine sometimes produced odd-looking results, like limbs rotating into physically impossible positions. This year, EA Canada went in and tuned the musculoskeletal structure of its players, accurately modeling biomechanical variables such as tension in joints, to deliver more realistic collisions.

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The implementation of physics in FIFA 12 had an unforeseen consequence: the in-game referees stopped knowing when to blow the whistle. They could no longer "understand when a collision started [versus] when a meaningful collision started," according to gameplay producer Aaron McHardy. So EA Canada had them err on the side of caution — that is, on the side of calling too few fouls, as opposed to being overzealous with the whistle.

"The complexity of that problem was mammoth," said McHardy, adding that "these things are difficult problems to solve using purely mathematics." The team knew the situation in FIFA 12 wasn't ideal, but McHardy told me, "I was quite proud of the guys, to be able to make the rules system work as well as it did last year." For FIFA 13, EA Canada reworked its referees, in addition to adding new features to the physics system, to ensure that fouls are called accordingly with contact.

A similar problem arose during the development of FIFA 13. First Touch Control, which governs the variability in the way a player "traps" a ball (i.e., receives a lofted pass), is a major new feature this year. It introduces "contextual trap error," so footballers aren't able to perfectly trap a 20-foot-high goal kick at midfield. A ball might bounce off a player's foot and skitter a few feet away, forcing him to make an effort to secure it, lest the opposing team take control. It's based on a variety of factors, including the player's skill level, the pressure from nearby defenders, the height and speed of the ball, and the weather.

"The complexity of that problem was mammoth"

The system is intended to provide a more realistic simulation and create opportunities for possession change. But in early iterations of First Touch Control, before EA Canada properly tuned the system, it was overly difficult to corral passes. The developers went to great lengths to make the trap error reasonable — to balance realism with fun. They wanted to "make sure that it's not a case that every time you get the ball, it takes you five or six touches to get it under control," said executive producer David Rutter. "What we're not trying to do," he told me, "is introduce frustration."

They're on the right track. I played a match of FIFA 13 last week, and appreciated that my midfielders couldn't trap goal kicks merely with a single soft tap from their feet. Jostling with opponents — an action made possible by this year's updates to the physics engine — gave them trouble, and I was even happier to see fouls called when the defenders pushed too hard.

In a sports video game, all of these complex systems have to work in concert with each other to deliver a realistic simulation. It's a tough balancing act, and developers must constantly make adjustments to maintain that harmony.

FIFA 13 is due out this fall for Xbox 360, PlayStation 3, Wii U, PC, Mac, Vita, 3DS, Wii, PSP, PS2, and iOS.