The Illusion of Intelligence - A Talk by Halo's Chris Butcher and Jaime Griesmer
AI is broken down into multiple subsections, some of the responsibilities are down to the designers, such as mission objectives, scripting and object placement, while other tasks are the responsibilities of programmers such as firing patterns, path-finding etc. However, some parts overlap, such as combat behaviours which is what this talk is mostly about.
The next design goal that Butcher and Griesemer talk about is making the AI interactive. In Halo one of the techniques they used to achieve this was through the different AI's reactions to the player on first sight, for example; Grunts are afraid of the player and might try and run away whereas Elites will be angered at the sight of the player and try to eliminate them and friendly marines will shower the play with praises, this is all an attempt to make the player feel like the most important person in the room.
"You could have the smartest AI in the world but it wouldn't matter if the player doesn't understand what the AI is doing" (Butcher and Griesemer, 2002). It is important to show the player what the AI intends to do next otherwise the player will see the AI to begin performing an action and not really understand what is happening. Butcher and Griesemer explain that they found their players had more fun when they were able to see the states the AI are in as it gives the players a chance to learn about what the AI is up to.
This makes the AI seem smarter as the player is able to follow the decision making process. If the players do not understand, then the AI becomes much harder for the player to predict. To show the state the AI is in Bungie made use of three main techniques;
[2] Nanopdf.com. (2018). [PDF] The Illusion of Intelligence - Free Download PDF. [online] Available at: https://nanopdf.com/download/the-illusion-of-intelligence_pdf# [Accessed 30 Mar. 2019].
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When designing AI the player should be taken into consideration and what they can do as "the first design goal was to make the AI intelligible to the player, so the player can understand what they're doing". (Butcher and Griesemer, 2002) This means that when designing the AI they had to work within limited capabilities because if the player is unable to understand what or why the AI is doing a certain action, it might as well not be in the game. So the player will assume that the AI is able to do what they can do such as; see what they can see, do what they can do and know what they can know. This is demonstrated with the Elite's shields which recharges exactly the same as the player's.
However, it is also important that the converse is followed so that the AI cannot do things the player cannot do or see things the player cannot see, an example of this would be that the AI will not hit every shot fired, as the player is quite likely to miss shots. These limitations are only guidelines, for instance a game like Battlefield will follow these guidelines closely due to the realism the game tries to portray and being set in a human environment all players and AI will be similar, however in a game like Halo with alien species the guidelines can be followed loosely as the enemies might be slightly different to the human protagonist for example they might be able to jump higher or move faster.
"A good rule of thumb should be that you can give an AI an ability the Player doesn’t have as long as the ability is recognizable and the limits of that ability can be easily predicted" (Butcher and Griesemer, 2002)Giving AI a transparent thought process also helps in giving the AI an intelligible appearance, this can be achieved through the use of animations and dialogue cues. This will help the player to understand why the AI is acting in the way that it is, such as the AI shouting "grenade" when one is thrown, either by the player or the AI. Alongside this Bungie also gave the different species their own personalities for example Grunts are a rather cowardly race and might try and hide when they come under fire from the player or even give up and run away if an Elite is killed near them, whereas Elites are the opposite to Grunts and are aggressive and will stand their ground.
The next design goal that Butcher and Griesemer talk about is making the AI interactive. In Halo one of the techniques they used to achieve this was through the different AI's reactions to the player on first sight, for example; Grunts are afraid of the player and might try and run away whereas Elites will be angered at the sight of the player and try to eliminate them and friendly marines will shower the play with praises, this is all an attempt to make the player feel like the most important person in the room.
"You could have the smartest AI in the world but it wouldn't matter if the player doesn't understand what the AI is doing" (Butcher and Griesemer, 2002). It is important to show the player what the AI intends to do next otherwise the player will see the AI to begin performing an action and not really understand what is happening. Butcher and Griesemer explain that they found their players had more fun when they were able to see the states the AI are in as it gives the players a chance to learn about what the AI is up to.
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This makes the AI seem smarter as the player is able to follow the decision making process. If the players do not understand, then the AI becomes much harder for the player to predict. To show the state the AI is in Bungie made use of three main techniques;
- Dialogue - Every AI character has some speech attached either in the human language or alien
- Postures - Sneaking, running, walking, etc
- Gestures - One time animation such as throwing a grenade or diving for cover
Dialogue makes use of tone of voice, so although the player cannot understand all of the different alien languages, the tone is fairly universal across all languages for anger, panic etc.
This was a very helpful talk, and although they didn't go into the behaviour tree side of the AI in Halo, the covered a lot of points that have made me rethink how my AI works and what aspects I would change if I had the time.
Reference List
[1] Butcher, C. and Griesemer, J. (2002). Creating the Illusion of Intelligence: Where AI and Level Design Overlap in Halo’s AI. [online] Gdcvault.com. Available at: https://www.gdcvault.com/play/1022590/Creating-the-Illusion-of-Intelligence [Accessed 31 Mar. 2019].Reference List
[2] Nanopdf.com. (2018). [PDF] The Illusion of Intelligence - Free Download PDF. [online] Available at: https://nanopdf.com/download/the-illusion-of-intelligence_pdf# [Accessed 30 Mar. 2019].