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BioShock Infinite’s Elizabeth owes her believable AI to Shakespeare

Posted on March 18, 2014 AT 01:14pm

In a GDC 2014 talk entitled “Bringing BioShock Infinite‘s Elizabeth to Life: An AI Postmortem” Irrational Games lead programmer John Abercrombie revealed that the beloved companion character’s behavior had an unlikely source of inspiration: the theater.

Abercrombie said that over the course of the project, Irrational’s AI programmers gradually came to understand that the best way to make Elizabeth believable and visible to the player was to borrow elements from stage productions, concepts like blocking, exaggerated gestures, exclamations, and improvisation.

One of the biggest indicators of the challenge that needed to be overcome, Abercrombie explained, was the simple task of making Elizabeth feel like a plausible partner during the game’s non-combat, exploration-driven segments. In an early implementation, the team tried having her follow the player, but that led to what Abercrombie termed “a comedy of errors,” where players would awkwardly try to follow Elizabeth as she tried to follow them, oftentimes struggling to keep her onscreen. A later attempt had her attempting to guess where the player was headed and anchor to a point along that path. Not only was this approach difficult, but it also led to strange behaviors, like awkward, sliding movement and a tendency to run straight into game geometry.

The final decision was to focus on situating Elizabeth in what Abercrombie referred to as a “goal side” position, borrowing a phrase from another unlikely field, soccer. That meant finding out where the player’s next gameplay goal was and charting the path there, then placing Elizabeth near a point ahead of the player on that path, close enough to feel connected but not awkward. On top of this, the team then layered other blocked and improvised behaviors, like interactions with nearby points of interest along that pat.

Combat, Abercrombie said, presented its own set of challenges. Originally, the team wanted Elizabeth to stay onscreen as much as possible, so they tried sending her to cover in the player’s line of sight. That led to situations where she would seem to lack any sense of self-preservation, running between enemies and players just to take cover behind visible objects.

Eventually, the team realized that players were too invested in combat to notice whether or not Elizabeth was actually on screen, so they settled upon the idea of having her operating in the background, trying to deliver support items. At first, players needed to physically walk up to Elizabeth for her to toss them the items, but  Even then, he admitted, it took a while to find the sweet spot. “For a while, we had it really long, like she was a football quarterback,” he joked.

Irrational Games head Ken Levine recently announced the studio will be winding down, making BioShock Infinite and its upcoming DLC their final projects. For more on the game, you can check out Andrew’s review.

Josh Harmon, Associate Editor
Josh Harmon picked up a controller when he was 3 years old—and he hasn't looked back since. This has made him particularly vulnerable to attacks from behind. He joined EGM as an intern following a brief-but-storied career on a number of small gaming blogs across the Internet. Follow him on Twitter @jorshy. Meet the rest of the crew.

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