Grzegorz Mazur, Co-Boss / Programmer, Vile Monarch

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