It took years of iteration - and some disastrous results - before Irrational made Elizabeth feel less like a robot and more of a character.
By Patrick Stafford on March 19, 2014 at 7:24 am
Irrational Games may have all but shut down, but its developers are very much out in force at this year’s GDC in San Francisco – and have revealed some key secrets and failures about the development of BioShock Infinite.
Specifically, lead programmer John Abercrombie gave a talk today showcasing the creation of Elizabeth, and her complicated and well-received artificial intelligence – something the team struggled with immensely, Abercrombie said.
“In my last six years of development haven’t had something as challenging or satisfying,” he said, adding the role of the AI team was charged with making the player believe Elizabeth was a living, breathing character.
Elizabeth received a lot of praise as a companion – she didn’t simply follow the player, but acted as a real person, walking alongside the player character, providing contextual dialogue, and interacting with objects and characters in a surprisingly realistic way.
But it didn’t start out this way. Abercrombie showed several pre-alpha videos of Elizabeth as the team figured out how to make her work.
The false starts
“We struggled in a number of ways in the creation of Elizabeth,” he said. “Most difficult was how to navigate the world in non-combat situations.”
“Many games have scripted companion characters. Given our desire to have an organic character, this would have created an explosion of content for programmers that would have been unmaintainable.”
One early method had Elizabeth follow the player around, but Abercrombie quickly showed the “disastrous” result. Elizabeth would wander off screen far too often, and test players would follow her for some reason, ending up in a circle.
Another video screened at the talk showed Elizabeth moving via a prediction system – she would guess where the player was going. She ended up just wandering into inanimate objects.
Let’s go to the theatre
In the end, Irrational took inspiration from the world of theatre to help move Elizabeth around. Using the concept of “blocking”, which actors use to determine where and when to stand on stage during a scene, the team was able to adapt Elizabeth to different situations using a system they called “smart terrain”.
This enabled Elizabeth to walk around an environment, without remaining too close or too far away from the player. (To remind players of where she might be, the team made her say or do certain things – like sigh, or murmur).
As for combat, that was an entirely different problem. Abercrombie showed pre-alpha versions of the “item tossing” used in the game, but they were very clunky and unhelpful – one version made the player walk up to Elizabeth to retrieve ammunition.
Over time, the system grew more complex. To make Elizabeth feel like a real person, the team made her gesture towards approaching enemies – and, again using inspiration from the theatre, the game used a “spotlight” to highlight enemies.
“But I feel like this is just the tip of the iceberg,” Abercrombie said, in relation to the future of intelligent companions, imploring attendees to make characters feel “more like a participant…and less like observers”.