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How 343 made Halo Infinite's bots play like humans


In a series first, the upcoming Halo Infinite has bots. And not just any bots - as I reported, Halo Infinite's bots aren't messing about.

Developer 343 used the recent Halo Infinite technical preview to gather feedback on bot behaviour and online performance. To that end, the technical preview debuted with the Bot Arena playlist, which put four players against four bots on arena maps.

Cover image for YouTube videoDF Direct Special: Halo Infinite Technical Preview Tested on Xbox Series X|S, PC, Xbox One X|S
John Linneman, Rich Leadbetter and Alex Battaglia spend the best part of 40 minutes sharing their thoughts on the Halo Infinite technical preview.

As 343 pushed the bot difficulty lever over the course of the technical preview weekend, the AI became more deadly. These bots were accurate, aggressive and ruthless. They would come in for a well-timed melee hit after dropping your shield. They would dodge grenades. They used grenades well and often. They picked up power weapons and they were not afraid to use them.

Once, a bot used the grappleshot to fly towards me before smacking me in the face with the gravity hammer. I even had a bot outsmart me as I danced around cover.

Don't get me wrong - you can tell Halo Infinite's bots are bots. But they're perhaps the most lifelike bots I've ever faced in a first-person shooter. They're pretty impressive.

If you had told me that Halo would add bots that could style on me like this, I would have called you a liar from r/halo

In an email interview with Eurogamer, senior lead gameplay engineer Brie Chin-Deyerle and multiplayer designer Sara Stern explained how 343 went about creating Halo Infinite's bots.

At a base level, Halo Infinite's bots are designed to be good training partners for players, whether they're new to the game, fancy a quick warmup before competitive matchmaking, or just want a relaxing experience.

To achieve this, 343 tried to make the bots mimic actual player behaviour as best it could, and this led the developers to create a new set of behaviours and tuning parameters for the game's AI systems.

Cover image for YouTube videoHalo Infinite | Multiplayer Overview

But how do you model player behaviour? 343 used internal playtests to watch players at different skill levels on the team, to see how they moved, what they focused on, and how accurate they were with different weapons. "As an example, highly skilled players strafe very differently than players who are just getting started," Chin-Deyerle and Stern said.

"We aimed to have the different bot difficulties represent the movement cadence and combat behaviors of players with different levels of Halo experience. We wanted our bots to feel human enough that they were helping players develop the right skills to make them successful in matchmaking."

One thing players of the technical preview found was the bots were happy to spam grenades - particularly after 343 upped their difficulty. Even though going up against grenade spam can be a frustrating experience, 343 felt it was important for the bots to chuck the things because that's what players do.

"The way bots engage in combat (including the way that they throw grenades) is designed to mimic what human players do," Chin-Deyerle and Stern said.

"Grenades are an important part of success in Halo's combat, and one of the best ways to learn that is by going up against a human (or bot) who knows how to use them."

I got destroyed by this bot from r/halo

It's a similar story for the bots' ability to jump over you and melee you in the back - a play I was surprised to find myself on the receiving end of during the technical preview.

"Seeing a streamer shocked at getting Ninja'd made us laugh right along with them," Chin-Deyerle and Stern said.

"It's one of the emergent things they can do as part of their combat dance. Bots often jump as part of combat, and if they happen to decide to jump when you're within melee range, you may find yourself learning a good lesson about respecting the space of other players."

Now the technical preview is over, 343 is going through the data to make changes in time for Halo Infinite's release later this year. One thing the team didn't realise ahead of the technical preview was that the Spartan difficulty - the hardest bot difficulty available - had some "quirks" that made them feel easier for players to kill, especially in 4v4.

It turns out, this player sentiment was right. The Spartan bots were easier than the ODST bots, Chin-Deyerle and Stern confirmed. Elsewhere, the skill data has helped the team identify some additional bugs and tuning issues that need to be resolved.

Yo these bots need to chill from r/halo

We've already discussed why Halo Infinite's bots won't teabag you. Chin-Deyerle and Stern reiterated Halo Infinite's bots do not mimic some human social behaviours. So no taunts, either.

"Bots are there to help you learn how to be better at Halo, and punishing you for making mistakes is the exact opposite of what we want," Chin-Deyerle and Stern said.

"Making mistakes means that you're getting out of your comfort zone and improving a skill you haven't mastered yet, and it's the only way you can get better. A bot will never judge you for missing with the sniper rifle, even if it's trying to make you work hard to land a headshot."

And finally, what's the story behind the amazing bot names?

"The names are a collection of development nicknames for people on the team, inside jokes, and other references that are important to the many people who helped create multiplayer," Chin-Deyerle and Stern said.

"We've been working on this game with one another for a long time, and we wanted the bot names to honour both the team and the fun we've had making it together."