Artificial Intelligence in Video Games

1. Artificial Intelligence in Video Games Jason Fuller

2. What is Game AI? • Imitate intelligence in the actions of non-player characters (NPCs). • Make the game “feel” real. • Obey laws of the game • Show decision making and planning

3. Goals of Game AI • Be fun! • Be challenging but not overwhelming (unless the hardest difficulty is selected) • Make sure the AI does not cheat! (At least do not get caught) • AI often get bonuses when difficulty increases • Do not hog all the resources! (CPU time)

4. Types of Games • Action games • Shooters (FPS and Third-Person) • Racing, Sports • RPG games (Role Playing Game) • Often include many action game aspects of AI • RTS games (Real Time Strategy)

5. Game AI Types • Action and RPG AI tend to work better with Finite State Machine based AI • RTS AI used Finite State Machines in the early years of AI development. • RTS AI work best with Artificial Neural Networks and Fuzzy Logic • Both contain path finding components

6. AI Path Finding Dijkstra’s Algorithm A* Algorithm • Most commonly used • Finds the shortest path • The world or map of the game is represented by a grid of points

7. A* Algorithm • Allows for high optimization • Either by changing the search algorithm to better suit the game or by changing the data structures. • Very similar to how people move between locations in a city.

8. Finite State Machines (FSM) • Simplest and most basic AI model. • Consists of: • States • State Transitions • Most common for Action games! • Not many different actions for NPCs

9. Finite State Machines • Among the States and State Transitions there are 4 components: • States which define behavior • State transitions which are the movement from one state to another • Conditions which must be met for state transition • Events/Actions which are internally or externallygenerated which may lead to a state transition

10. FSM Example

11. FSM Disadvantages • Very predictable • Too many states get tough to organize • Since there are such crisp rules between states, NPC does not feel natural

12. FSM within a State • States have a FSM within them

13. Modern FSM Example

14. History of Finite State Machines • In 1952, the game Nim used AI to play against an opponent. • 1960’s & 1970’s • Spacewar! • Pong • Space Invaders • 1980’s • Simcity

15. History Continued • 1990’s • Dragon Quest IV • Warcraft • Half-Life

16. Artificial Neural Networks (ANN) • No agreed definition, most common one is “a network of simple processing elements, which can exhibit complex global behavior, determined by the connections between the processing elements and element parameters.” • Mathematical model inspired by biological neural networks. • An adaptive structure that can learn.

17. ANN Structure • Very similar to the structure of our brain. • Input layer, processing (hidden) layer, output layer • Learns by example

18. ANN Structure • The hidden layer is not just a straight line of nodes • Each node in the hidden layer will contain just a small part of the overall calculation • The nodes have connectionsbetween each other withcertain weights

19. ANN Structure • The weight of the connections between the nodes determine the outcomes of the calculations • If a node is triggered by 2 different nodes it can then determine which one is more important

20. ANN Learning

23. Black & White • Came out in 2001 • First to effectively useArtificial Neural Networks

24. Halo Wars • Came out in 2009 • Featured a “Custom” difficulty level that used Artificial Neural Networks

25. Fuzzy Logic • Introduced in 1965 for use in Artificial Intelligence research • Present problems to computers in a way similar to how humans solve problems and that everything is a matter of degree (or preference or context).

26. Example Problem A store owner needs to decide how much produce to order. Elements to take in to consideration: • Time of year? • What is the weather like? • Is there a Holiday coming up?

27. Video • Fuzzy Logic: An Introduction

28. Games Now that the major types of AI have been covered, I will go into more detail about what games they are used in.

29. Racing Game AI • Large-scale cheating! • AI already know the track and optimal path • AI already has complete behavior determined before the start of the race

30. Racing AI graphs General Path Optimal Path

31. Racing Game AI • In its basic form, it is the most basic of game AI but in some of the racing simulators, the AI are more complicated • If the player is using the optimal path, the AI will actively try to push them off of it. • The AI will also use tricks such as spinning out opponents by making their back tires lose grip.

32. FPS Game AI • Implemented with a layered structure • Bottom layers control the path finding tasks and animation selection • Higher layers control the tactical reasoning which is where the Finite State Machine would be.

33. A* Graph of FPS or RPG World General path Playable Zone Unplayable Zone

34. FPS Continued • F.E.A.R. series has revolutionary AI • AIs have knowledge of map elements and will flank the player • AI will break through walls and windows to get to the player • AI will rush when they heavily outnumber the player

35. RPG Game AI • Many encounters with AI are unscripted • GTA IV and Far Cry 2 made great leaps in “friendly” AI

36. Elder Scrolls IV: Oblivion • Released in 2006 • During testing, a story important NPC kept being found dead. • A mechanic of the AI was the cause.

37. Bioshock Infinite • The player companion, Elizabeth (who is an AI), is almost entirely unscripted.

38. RTS Game AI • Started out using Finite State Machines to control AI • Too many options to cover • AI was “dumb” • AI would build up in a strict way • Once the player found a strategy that worked against the AI, it would always work. • RTS AI switched to a combination of Fuzzy Logic and Artificial Neural Networks

39. RTS Game AI • By changing to Fuzzy Logic and Artificial Neural Networks (ANN): • Fuzzy Logic led to smarter responses to attacks • ANN led to smarter development of base and better long term decisions

40. A* Graph of RTS Map

41. RTS Continued • Maxis is again changing the simulation landscape with the new Simcity • Every “Sim” is a full AI • Have there own agenda • Have specific wantsand needs

42. Video • SimCity: Economics AI

43. Future of Game AI • Game AI have made great leaps forward since they were first developed. • An AI that can learn how you play a game would be a great opponent

44. References • Champandard, Alex. "Top 10 Most Influential AI Games." Aigamedev.com. N.p., 12 Sept. 2007. Web. 25 Feb. 2013. <http://aigamedev.com/open/review/top-ai-games/>. • Grant, Eugene, and Rex Lardner. "The Talk of the Town." TheNewYorker.com. The New Yorker, 02 Aug. 1952. Web. 25 Feb. 2013. <http://www.newyorker.com/archive/1952/08/02/1952_08_02_018_TNY_CARDS_000236053>. • Grzyb, Janusz. "Artificial Intelligence in Games." - CodeProject. Software Developer's Journal, n.d. Web. 25 Feb. 2013. <http://www.codeproject.com/Articles/14840/Artificial-Intelligence-in-Games>. • "Neural Networks: A Requirement for Intelligent Systems." N.p., 2007. Web. 25 Feb. 2013. <http://www.learnartificialneuralnetworks.com/#training>. • "Short Term Decision Making with Fuzzy Logic And Long Term Decision Making with Neural Networks In Real-Time Strategy Games." Hevi.info. N.p., n.d. Web. 25 Feb. 2013. <http://www.hevi.info/tag/artificial-intelligence-in-real-time-strategy-games/>.

45. Videos • Fuzzy Logic http://www.youtube.com/watch?feature=player_detailpage&v=P8wY6mi1vV8#t=117s • SimCity http://www.youtube.com/watch?feature=player_detailpage&list=UUnje_8ilXP7KB2vdssyAWug&v=MxTcm1YFKcU#t=37s

46. QUESTIONS?