1. Games and AI

2. History or Why games anyway?

3. Games and Puzzles Checkers Chess Missionaries and Cannibals
Monkey and Bananas Go

4. Game types Two player – zero sum
With full knowledge (e.g. Tic-Tac-Toe)
Partial Knowledge (e.g. Poker)
Video games
Military games
Negotiation games

5. AI in Games
How to implement decision making

6. Decision Making
Internal
State
Decision
Logic
Action
External
State

7. Decision Trees Build a tree of choices Node types: Boolean Enumeration
Numeric value (values in ranges)
3D vectors (e.g distances)

8. Good for structured decisions
Can reduce complexity since not all conditions are checked
Depth of tree is limit on performance
O(log n), but worst case is O(n)
Works directly on elementary data

9. State Machines Adds simple memory Input is perception of situation
Used to record the current action/situation
Input is perception of situation
Issue: a perception can be a complex combination of elementary data

10. Hierarchical State Machines
Two extensions:
For design
State machines can be combined into a single machine - just like programs
Separation can be used for structuring
For exception handling
Emergency procedures called like a subroutine

11. Combining Decision Tree and State Machines
Use decision tree to collapse raw data to perception

12. Fuzzy Logic Classical Predicates are boolean Fuzzy Predicates
Hungry(Bob)
Fuzzy Predicates
Hungry(Bob) = 0.9

13. Fuzzification
Healthy
Hurt 1
Input Value

14. Fuzzy Logic Combinators
Not A
1-mA
A and B
Min ( mA , mB )
A or B
Max ( mA , mB )

15. Rules Define membership in a set by fuzzy logic
m(take action) = m(A) and m(B)

16. Defuzzification Use a threshold to get a boolean
Use set of thresholds for an enumeration
Use highest value for overlapping sets
Center of gravity

17. Center of Gravity

18. Markov Processes State is numerical value
State vector is a set of values.
Transition is a matrix operation
V’ = V x M
Each move has a matrix

19. Example Sate vector gives the safety of 4 locations player can be in
When player takes an action, the safety changes

20. Goal-Oriented Behavior
Players can have a set of possible goals and a set of actions.
When a goal is active, use a planner to select actions to achieve the goal

21. Rule-Based Systems If <conditions> then <action>
More about rules next week!

22. Summery
Choices!