Source

1. AI “I have always tried to teach the AI the same successful strategies that I use in playing a game”. – Brian Reynolds (Civilisation II & Alpha Centauri)

2. Source • Rouse, R., (2005) Game Design, Theory and Practice (2nd ed.), Wordware Publishing Inc., Plano Tx USA, chapter 9.

3. Turing Test: • Humans are provided with terminals • They type sentences • A machine provides responses on screen • If humans believe that responses provided by human, the machine has passed the Turing test.

4. Depth of AI • In games, AI tries to make the game fun • Game’s AI may be completely random • Game’s AI may be completely logical • Bigger challenge to design behaviours and movement patterns • E.g.: Tetris selects the next block at random.

5. Depth of AI • Degree of AI depends on the game • In RPG (role playing game) expect high level of AI • In Sims, the AI is the game • (NPC = non-playing character = AI driven)

6. Rules of AI • AI must not do silly things • High standard expected from “human” characters (the Uncanny Valley effect) • Non-humans don’t need to be so clever • Nevertheless, dumb behaviour destroys the game experience

7. Making AI Appear Human • AI must be unpredictable • Humans are unpredictable • If game behaviour is predictable, the fun stops • Players need surprise • Surprise can be as simple as a random number generator

8. Making AI Appear Human • Players attribute intelligence even if actions random, “What’s it trying to do?” • Fuzzy logic: randomness weighted so as to make good strategies more likely • Or small amount of randomness added into cold logic to add surprises • Try not to let randomness get in the way of enemy strategy

9. Storytelling • AI assists storytelling • Better to show than to tell • CAN show that citizens frightened in a cut-scene • BETTER: program citizens to avoid the player • Dynamic storytelling: NPC responds to how you treat it – either helps you or opposes you.

10. Storytelling • AI can create a living world • There are NPCs which are part of the game • Other NPCs simply set the scene – make the player feel less lonely.

11. The Sloped Playing Field • Humans are usually smarter than AI • Not realistic to give each a fair chance, so: • There are more of them than us, They never need to reload, We have to shoot them while they only need to touch us • Victory against insurmountable odds is far sweeter!

12. AI and the Environment • Stupid NPCs sometimes get stuck in corners • Need to match the design of the level to ability of NPC to navigate - compromise • Levels and NPCs are usually designed by different teams, so it doesn’t always work first time • If the NPC is on the player’s side, make very sure it won’t let her down.

13. Scripted Behaviour • If there is something really tricky for an NPC to do (swing on a rope?) – script it. • Don’t use too much scripting – it looks and is predictable • Can switch between scripts, randomly or intelligently • Common to script “human” guides who lead and advise at various points • Guides tend to be big talkers! • If a guide leads, program the end-point but use AI to decide the route

14. Policy and Programming • Game itself is anthropocentric (revolves around human player • NPC interacts with human player: • Simple reactions (eg shoots back when shot at) • General attitudes (behaviour depends on how treated) • Complex intentions (agenda of own)

15. Where to put the intelligence • The more restrictive the game world is, the more complex the NPCs need to be • eg: If the game world allows NPCs to walk into a fire, we need to programme the NPC not to • If the game world prevents anyone from walking into the fire, NPC programming becomes easier

16. Humanness and Stance Humanness: • NPCs are limited in humanness – so multiplayer games can look far more realistic • Even minor displays of emotion can make a character look more human • Humans unconsciously try to read humanness into character actions • If the game world is interesting to watch, it will also be enjoyable to participate in

17. Humanness and Stance Humanness: • There are games which don’t have human players (eg: Sims, Singles) • Humans remain as non-participating observers • Enthusiastic watchers: parents and coaches watching protégés and own children

18. Humanness and Stance • Stance: • Enemy • Ally • Observer

19. Humanness and Stance • Stance: Enemy • Traditionally NPC is an enemy • Must show intelligent or at least purposeful behaviour • Illusion that NPC is at same level as the human player

20. Humanness and Stance • Stance: ally • Reconnaisance officer must provide data in a visually accessible format • Human players require consistency, even at the expense of complete data. • NPC allies can even take on tasks for player

21. Humanness and Stance • Stance: neutral • NPC is observer (camera operator, commentator) • NPC is referee (football) • Can simply be part of the story • An extra • There to provide atmosphere • Assist immersion

22. The MVC Model Model - View - Controller

23. The Role of the Computer • Coordinating the game process (eg realising a participant’s move in a chess game according to the rules • Illustrating the suituation ( e.g. displaying the chessboard and pieces on the screen) • Participating as a fellow player

24. The MVC Model • Developed by the Smalltalk community and adopted by the object-oriented world. • The underlying application domain (Model) • The way the scene is presented to the viewer (View) • The way the user interacts with the game (Controller) • These should be kept separate.

26. Model • Includes software components that do coordination: evaluate rules, uphold game state • Rules and basic entity information (eg gravity and other physical laws) form the core structures

27. Model Core structures need not cover all rules as they may be instantiated: • Core structures cover basic mechanism and properties of eg playing cards • Instance data provides additional structures needed for game (eg ranking of hands, stake handling, resolving ties)

28. View Section • Handles the presentation of the game state to human and synthetic playeers • Rendered view goes to output device for human players. Sometimes customisable. Includes audio. Can include sensory feedback (rumble) • Synthetic view goes to synthetic (AI) player. Has coordinates and mathematical data - more useful than rendered form.

29. Controller • Controller allows human and synthetic players to input moves into the game • Controller can exclude illegal moves suggested by the player • usually human input enters controller through an input device and driver software. • Configuration component initialises the game.

30. Extensions of MVC model • Diagram only shows one player and one AI synthetic player. There may be many • The model may be distributed over many computers

31. Directed study: • Download Doom95 and play it • Note especially the behaviour of the monsters • What do they do when they aren’t engaged? • When do they engage with you • What do they do while engaged? • Do they help each other?