The leading role of the director is to manage the ‘menace gauge’, which is a tool the game uses to monitor tension levels in the game. Controlling the tension levels in the game, this system will occasionally tell the alien to head to a location near the player, raising the tension. Equally, the director will tell the alien when to back off, so as to maintain the ebb and flow of anxiety. The director’s role is to decide whether the alien is in an active or passive state. All of this is done via a Utility AI; an effective way to model behaviors of non-player characters in games. By scoring the relative benefit of different behaviours, it can select the mathematically correct action for any given moment.
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Adaptive Difficulty: How AI makes Games more Immersive
From Scripts to Dynamic Action
The gaming industry is constantly evolving as technology advances and the expectations of a fresh experience for gamers is a mounting pressure on game development studios. Artificial Intelligence (AI) has become an increasingly crucial tool within game development, influencing and supporting the creation of many aspects of games such as; Non-Player Character (NPC) responses, generative worlds and adaptive difficulty.
AI applications in video games: Adaptive AI & Generative AI
Adaptive AI and Generative AI have very different roles to play within game development. A game studio can apply both types to a game or only choose to utilise one type. Both adaptive and generative AI, when applied right, can create a dynamic experience and encourage prolonged engagement from gamers. Adaptive AI takes pre-existing game elements (game mechanics, character models or a dialogue database) and ‘adapts’ them in response to the actions taken by the player. This creates the sense of a living game world that acknowledges the decisions made by the player.
Generative AI focuses on producing entirely new elements from scratch based on the actions taken by the player. These new elements could be entirely new worlds to explore or something smaller, such as new dialogue from NPCs. No matter the result, generative AI is used to ensure replayability on a grander scale than the scripted games we’re accustomed to. Whilst both adaptive and generative AI have their place in game development, this blog focuses on exploring the benefits of adaptive AI and it’s successes in the gaming world.

Alien: Isolation
Released in 2014, Alien: Isolation set out on a mission to recreate the near insurmountable tension and impending doom you feel while watching Ridley Scott’s Alien (1979).
The mission statement was simple, the player must feel what it’s like to be hunted by the ultimate killer. Breaking away from the traditional approaches seen previously in run and gun game, Alien 3 (1992), and first-person shooter Alien: Trilogy (1996) Alien: Isolation, is a survival horror game that only offers stealth mechanics as tools to survive. The player being powerless throughout was a stark change to expectations of AAA game development at the time. Replayability was a crucial factor for Creative Assembly, whilst scripted jumpscares would have been an easy scare tactic they’re predictable and lose effect quickly. Opting instead to generate fear through the unpredictability, as described by Andy Bray at the 2016 nucl.ai conference. The unpredictability comes from growing and waning tensions, lulling players into a false sense of security. Andy Bray, Lead AI and Gameplay Programmer, describes their design ethos: “‘Psychopathic serendipity’: the alien always find itself
in the right place at the right time.” All this had to be done without being scripted, as they wanted the player to feel mortal dread each time they play, not just the first time, and that’s where the AI system comes in.
When developing the AI system, there are two core principles that were significant; the system had to make sure the Xenomorph served its purpose but also, plays according to expectations. This lead to the creation of two specific behavioural management systems. That’s right, the AI system in Alien: Isolation is actually TWO entities.
The Director

The Alien

Reliant upon behavior trees, the alien has access to over 100 nodes that dictate what type of actions are taken whilst navigating the game and hunting down the player. Certain parts of the behaviour tree are locked at the start of the game, only being unlocked based on player behaviour - giving the alien the tools to perfectly hunt YOU, the player. It keeps you on edge, pressuring you into stepping out of your comfort zone. The alien is also fitted with sensors that are triggered whenever a player walks/runs and shoots their gun. Additionally, it has short range tracers in the back of its head that act like eyes to ensure that the player doesn’t avoid detection by stalking behind the alien.
Unlike the director, the alien isn’t all knowing. A lot of the movements it makes are hunting down and stalking around the environment. Anyone who has played Alien: Isolation will have noticed at one point or another, that the alien doesn’t always move with purpose. It can be observed wandering into rooms that the player isn’t in and sometimes even doubling back in them shortly after. This is a result of the AI behavioural model having key points of interest, responding dynamically to nearby locations or designated areas as specified by programmers. What’s special about this, is the sub-optimal routes often taken during these moments. By rechecking rooms it’s just been in, it gives the alien a sense that it’s searching, doubting itself and hunting down hidden prey. These moments give the player the sense of accomplishment, ducking past the alien as it rechecks an incorrect room are second to none. It also makes those moments where it does hear your movement all the more
terrifying because it gives the player a direct comparison between a success and a failure to avoid detection - raising the emotional stakes to hide and recover from the mistake, if you can.
It’s common in horror video games, for developers to allow their monster to ‘cheat’ by teleporting whilst offscreen, allowing them to catch players off-guard at the worst time possible. Alien: Isolation doesn’t do this, despite how good the behavioural model may make the Xenomorph seem, the alien is limited to physically walking around the station like the player. There are only 2 instances in which the Xenomorph teleports in the entire game and that is to ensure that the model can appear in cutscenes.
Alien: Rogue Incursion
We are already seeing the expansion into generative AI in the Alien game series with recently released VR game Alien: Rogue Incursion. Through the use of NVIDIA ACE, which stands for Avatar Cloud Engine, is NVIDIA’s latest technology suit. By utilising NVIDIA Audio2Face, developer Survios have generated entire facial animations on their characters only using the recordings of voice actors reading their lines.
Whilst playing Alien: Rogue Incursion, which is available on PCVR and PSVR2, you encounter other survivors all of which have been powered by NVIDIA’s Audio2Face. Traditionally, the game developers would have to animate this by manual animation or facial mocap. Unfortunately, when done this way, you often see that only the mouth is animated, which can be immersion breaking for many players. As technology advances, we’re seeing the quality of animation within video games improving dramatically. NVIDIA have been at the forefront of a lot of these advancements.
NVIDIA have released a short demonstration video so you can see for yourself the technology in action. The character you are seeing is Davis 01, a synthetic companion character for Zula. Be warned, this video does contain spoilers if you haven’t played the game yet.
Final Thoughts
Adaptive AI within video games, when applied right, can bring a level of unpredictability that keeps players coming back to replay it over and over again. Alien: Isolation is a fantastic demonstration of adaptive AI used brilliantly. Even now, over a decade after it’s release, people are still considering it one of the best horror games ever made - a large portion of that being because of the AI. Developer Creative Assembly have announced that Alien: Isolation 2 is in development, which is terrifyingly exciting news. Not many details have been shared with us as of right now, but Alistair Hope returns to lead development which is a good sign. With the release of NVIDIA ACE we might begin to see a rise in intelligent NPCs within video games, through their developments in AI powered autonomous game characters.
In anticipation of the release, my hopes are that the AI behavioural model is even more advanced than the first. As much as a scarier, smarter Xenomorph terrifies me, it’s a must for a sequel to a beloved game.