Grzegorz Mazur is the co-boss and technical director at Vile Monarch. He discusses various techniques used for artificial intelligence in video games, including scripted AI, finite state machines, behavior trees, and influence mapping. Behavior trees allow for more complex and emergent agent behavior than finite state machines by evaluating decision trees. Influence mapping represents game elements as influence maps that can determine strategic areas for troop movements based on tensions between opposing forces.

1. AI in Video Games
Grzegorz Mazur

2. Who we are?
Vile Monarch
Warsaw, Poland

3. Who I am?
● Co-Boss and Technical Director at
Vile Monarch
● Previously 11bit studios – Lead
Programmer of This War of Mine and
Sleepwalkers Journey
● Lecturer at Warsaw Film School
● Musician - amateur
grzegorz.mazur@vilemonarch.com
@dagenoth

4. What is AI in games?
● Interactive system that animates game world
● AI Agent
● Agent based on his state and game world state takes
action

5. What is AI in games?
Stimulus, for example:
- enemy in sight
- hearing call for help
- taking damage
State of agent, for ex:
- HP level
- resource quantity
- current goal
AI System
Action, for example:
- shooting
- playing animation
- beginning of movement
- command to move troop

6. What makes AI good for player?
● It should support gameplay...
● ... especially create challenge
● Good AI DOESNT have to be SMART

7. What makes AI good for developer?
● It should support gameplay... ;)
● Configurable
● Predictable
● Reusable
● Scalable

8. Scripted AI
● Simple scripts "if X then Y" and event-based programming
● Simple customization
● You have to predict everything
● Its hard to make it emergent
● It becomes drastically complicated with size

9. Finite State Machines
● In every moment Agent is in a single, specific state. For
example: combat, retreat, looking for enemy.
● State → specific behaviour
● Under specific conditions agent can make transistion from
current state to another

10. Finite State Machines
Idle
Combat
Following after enemy
Retreat

11. Behaviour Trees
● Node – complex agent behaviour
● Each node knows if he can run
● When node is running it tries to run its first runnable child
● Thats how tree-based decision structure appears
● At each moment only one branch of tree is running

12. Behaviour Trees
Enemy
Combat
Following after
enemy Idle

13. Behaviour Trees
Enemy
Combat
Following after
enemy Idle
Choos random
POI
[Range:5m]
Move
[Speed:3]
[Mode: Walk]
Play random
idle animation
[Loop: false]
[Time:5-10s]
Wait
[Time:5-10s]

14. Behaviour Trees
Enemy
Combat
Follow after
enemy Idle
Is enemy in
range
[Range: 1m]
Play animation
[Animation: hit]
Deal damage
[Damage: 30]

15. Behaviour Trees
● Sequences, selectors, actions, decorators
● After certain time/after certain stimulus we cen reevaluate
whole tree
● After reevaluation of tree a new branch can start running
● Behaviour trees look similar to hierarchical finiste state
machines

16. Behaviour Trees

17. Influence Mapping
● Method of finding areas in which we should move our
troops
● Game world represented by grid or graph

18. Influence Mapping
● Each unit/building/resource on
a map has its own base
influence – area and value
● Map of our influence
● Map of enemy influence

19. Influence Mapping
● Influence Map = Our
influence map – enemy
influence map
● Weight of area = influence
/ cost of movement
● Goal for troop = area with
highest weight

20. Influence Mapping
● Tension map = our influence + enemy influence
● The higher value – the bigger forces at the area
● Vulnerability map = tension map – ABS(influence map)
● The higher value – the bigger even fights at the area

21. Influence Mapping
● Based on information from different maps and additonal
conditions we can create any strategy
● Optionally we can introduce inertia and propagation of
influence
● Designer can introduce his own additional goal map
● Simple scripts are enough to make use of influence map

22. Influence Mapping

23. Other techniques
● Planners
● BDI
● Neural Networks
● Fuzzy Logic

24. Thank you!
grzegorz.mazur@vilemonarch.com
@dagenoth