Animating BioShock Infinite's Elizabeth to foster emotional connections

Elizabeth, the heroine and driving narrative force of Irrational Games' BioShock Infinite, is more than just the sum of her parts. In a session at GDC today, animation director Shawn Robertson discussed how every department at the studio was involved in Elizabeth's creation, and what narrative techniques and other systems went into bringing her to life.

To create Elizabeth's humanity, Robertson said, her character needed not only a narrative force but art and other systems — combat, movement and the like — working in tandem.

Humans in the first BioShock were introduced in tightly-controlled cutscenes with no interaction or behind glass walls, preventing players from building relationships with them. The relationships in BioShock were between the Big Daddies and Little Sisters, relationships inaccessible to the players. For BioShock Infinite, Irrational needed to create a true companion character, an AI who would be constantly by the player's side and interact with them in a realistic, meaningful way.

"We wanted to bring the story fully into the player space," Robertson said. "We wanted her to share that journey with the player. We wanted a relationship the player could emotionally buy into."

The first question developers asked themselves was: Would Elizabeth talk? There are great animation opportunities for a companion that didn't talk, but after testing a silent Elizabeth, they realized a mute character would be obtrusive to the player experience. By pointing out enemies or other objects, a mute Elizabeth would pull players out of the actions they were doing every time she needed to communicate. Robertson said the test proved they needed to cut Elizabeth — not an option — or move forward with a speaking Elizabeth.

A speaking Elizabeth meant motion capture for her face, which in turn meant more work for animators. After testing performance capture for her face, the team eventually scrapped using this system for hand-keyed animation. This was because they thought it looked better, there was less data to sift through and the studio wouldn't have to hire an actress. Using hand-keyed animation, however, meant a more time-consuming job.

Robertson said an enormous amount of effort went into Elizabeth's dress physics.

"There's a reason you don't see a lot of real-time characters wearing dresses," he said. "Once you close that geometry around those legs, it opens a world of problems."

Robertson said that when Elizabeth ran, animators had to make sure her legs poked her dress in a realistic way. Sometimes her dress would stay aloft because she was running so fast the dress didn't have time to move around her properly. Putting her in pants wasn't an option because in the time period BioShock Infinite draws from, women wore specific kinds of dresses. Pants or a tinier skirt wouldn't work.

When developing Elizabeth for the downloadable content Burial at Sea, animators had to create a new outfit and new content that already fit into her pre-programmed emotion and locomotion systems. Elizabeth went from her more innocent Columbia version to a femme fatale "with a two-pack-a-day smoking habit," Robertson said. New gestures were added to her repertoire, including the smoking animation, a more dramatic head tilt and a slinky hand-on-hip standing position.

Initial versions of "Booker, catch!" involved Elizabeth pulling weapons out of tears at random times — however this changed the story of the action. Robertson said players shouldn't be wondering where the weapon comes from, but that Elizabeth came to help you out in the first place. Elizabeth's "Booker Catch" action was then framed to be more about helping Booker reload and recover health than her pulling weapons out of nowhere. Changing this mechanic resulted in "war stories" being told around the Irrational office, with studio members telling tales of Elizabeth giving the ammo when they were down to one bullet at a crucial time or healing them with a split-second left in a fight.

"Pre-production is a great place to have fun, but you can't get stuck here," Robertson said. "You have to make tough decisions. Player experience is everything. But while failing is good, you want to fail quickly. You want to learn from your mistakes quickly. And if you have the opportunity to, fail from the player's point of view. You'll learn from that.

"I think we were all surprised by the little things we could do to make Liz feel more human," he added. "Each of these systems on their own was not that difficult to create, but the way they combined together presented a really robust version of humanity."