Hitman: Absolution’s killer AI
This is the third and final part in our series of previews of Hitman: Absolution. You’ll find our demo impressions here and discussion of its controversial new additions here.
For an AI programmer, stealth can be a headache. Protagonists who can attack from anywhere, at any time, mean AI-controlled foes have to be able to react spontaneously to assaults, rather than making use of easily anticipated cover points and lines of sight. In previous Hitman games, enemies would swing erratically between acting like complete dolts and displaying terrifying omniscience – a botched kill could all too easily snowball into a bloodbath when guards who should be none the wiser would take it upon themselves to rush to the scene.
According to Ulf Johansen, lead AI programmer on Hitman: Absolution, however, the realtime editing offered by IO’s new Glacier 2 engine has made ironing out AI quirks easier than before. At his workstation, he fires up the demo we’ve just seen, before switching on an a whole suite of annotations in the engine – Metal Gear Solid-esque sight cones spring from enemies’ heads, for instance, while individual NPCs’ ‘thought processes’ appear in realtime on an adjacent screen. “Imagine you want to know something, like, ‘why is this guy not searching?’” he explains, highlighting a guard who seems particularly uncaring about a gun battle erupting on the other side of the room – “Before, you’d [attempt a fix] and have to redo the level and wait ten minutes to see if it had any effect. Instead, we can just see it now.”
Lead AI programmer Ulf Johansen
But realtime editing has only been one improvement in the tech. “We’ve put in a system that coordinates the behaviour of the AI,” he continues. “They actually understand what’s going on with the other guys. That’s something we couldn’t do in Blood Money. We’ve also added a new component which we call the reasoning grid,” he says, before switching on said grid, causing the dark and musty floor of the library to become covered in green squares. “The grid spreads across the level – we can calculate information such as visibility and assign it to points in this grid to help the AI do better spatial reasoning,” he explains. As he speaks, 47 takes cover behind an empty shelf. The nearby area is covered in luminously bright squares which represent positions advantageous to the AI.
Johansen engages in a flowing battle among the library shelves 47 crept through when we were first shown the demo. As well as offering us a glimpse at an alternate approach to the checkpoint, the AI’s intelligent use of cover suggests a game in which gunfights will be more tactically satisfying than ever before. “We have gone for what we’d call a hero-centric approach,” says Blystad. “It will always centre on you – whatever you do, the AI will react to that dynamically.”