Making it in Unreal: how BioShock Infinite’s Elizabeth helped The Occupation

Recreating Elizabeth

The builders of the Manchester, UK-based White Paper Games are disciples of the immersive sim: the systemic, choice-driven likes of Thief, Deus Ex, and BioShock. They made a pilgrimage to GDC in 2014 to look at Irrational Games give a chat known as Creating Elizabeth – or, relatively, creating the AI that governs BioShock Infinite’s distinctive companion character.

Irrational shared their technique of working in Unreal Engine three, and White Paper have utilized the identical concepts to Unreal Engine four.

“We took the concepts that they used,” White Paper co-founder and designer Pete Bottomley tells us. “They have things called smart terrain objects that they place around the world that Elizabeth knows about and goes towards. She interacts with loads of different things.”

Moreover, Elizabeth has completely different states of being: completely happy, emotional, combat-ready.

“All these influenced our approach to AI,” Bottomley says. “Those kind of studios are using Unreal, so we can translate a lot of that stuff through. Creating Elizabeth was our benchmark – if we’re 10% of the way there then cool, we’ve done a good job as a small team.”

To that finish, the crew have leaned on Unreal Engine four’s blackboard system. A blackboard is solely a spot the place an AI’s information for decision-making may be written and browse. They’re typically used together with behaviour bushes, which is exactly how White Paper have used theirs.

“I’d never done anything like that before, so I was researching AI and how they’re supposed to talk,” Bottomley says. “It took us a while to figure out, between the behaviour trees and the AI logic, where it is that you include a voice line. The behaviour trees are supposed to be high level logic and decision making. It shouldn’t be storing 500 lines of dialogue.”

Growing confidence has seen the crew push for the sort of AI that’s necessary to their systemic, small-scale open-world, nevertheless. Since The Occupation performs out in real-time, all of its characters are given time-based duties to do. Internal logic tells a harassed NPC, for example, to go outdoors and take a break, or drink a espresso from the machine. If they do drink a espresso, they could have to make use of the bathroom afterwards. White Paper intend the sport’s AI to work together naturally with the world as typically as attainable – significantly when these interactions can yield thrilling gameplay prospects.

“If they go to the toilet when they should be in the office, that might be an opportunity for the player,” Bottomley notes. “I love the systemic and emergent elements of games like Dishonored, Thief, and Deus Ex. It’s just trying to be inspired by what those triple-A teams are doing. What is our nine-person approach to that? We’re trying to be smart about what our small team can achieve, and push production and interesting AI.”

Animating AI

White Paper discovered that, as their characters pathed their means round The Occupation’s constructing, the loops and repetition of their animation turned apparent. And in order that they’ve applied a couple of ‘loop-breakers’: whereas characters are strolling, they’ll generally scratch their pate or itch their arm. They’ve obtained head-look programs, too, so their eyes observe you round a room you maybe you shouldn’t be in.

“AI by default goes to a point, stops, and moves to another point,” Bottomley says. “It’s very linear. It’s good for run-and-gun shooters, but for believable AI, we introduced our own curved pathing system, so they know the corners and take them at a curve.”

It’s sufficiently spectacular that The Occupation’s debut trailer drew comparability to – guess what? – BioShock Infinite. And all of the extra spectacular whenever you be taught that, the place Irrational grew to 150 workers through the course of Infinite’s growth, White Paper Games have entry to precisely one animator. 

“We’re trying to think of the biggest pay-off we can get,” Bottomley explains.

A matter of time

“Everything in the world is based off time,” Bottomley says. “Instead of you hitting a trigger in the world to set off an event, events happen at a certain time.” 

Of all The Occupation’s excessive stage programs, nevertheless, its real-time conceit is probably the only. “The level logic is basically: the world knows what time it is,” Bottomley says. “We have an array of strokes which are the timed events. At 10:37 it will fire a custom event called ‘Clock tower rings,’ and the clock goes bong. That’s literally it. It’s the simplest system, but it just works.”

Since the sport has a common world time that’s all the time ticking onwards, the watch in your wrist and each clock on the wall pull information from that very same supply. Voila: prompt rigidity in a sport the place there’s no well being bar to lose, nor dwindling ammo in your gun.

“All of that [logic] allows the player to plan their time out,” Bottomley finishes. “Because that’s a big thing in an immersive sim: you’ve got this environment, you’re gonna plan and then execute upon those plans.”

There’s no launch date as but – however White Paper Games seem nicely on their method to executing theirs.

The Occupation is coming to the PC. Unreal Engine 4 is now free.

In this sponsored collection, we’re taking a look at how sport builders are benefiting from Unreal Engine four to create a brand new era of PC video games. With because of Epic Games and White Paper Games.