1. CIS 488/588 Bruce R. Maxim UM-Dearborn
AI Overview
CIS 488/588
Bruce R. Maxim
UM-Dearborn
11/23/2018

2. What is AI?
A form of intelligence artificially recreated using machines
A set of academic techniques, research methods, in problems that fall into one sub-branch of science
Algorithms and data structures that can be used to help a machine do something interesting without explicit programming
11/23/2018

3. Intelligence
Set of skills that allow humans to solve problems with limited resources
Learning
Planning
Imagination
Creativity
Non-player character (NPC)intelligence is the artificial version of human intelligence
11/23/2018

4. Academic AI
Historically AI has tended to be very focused on detailed problems solvable using specific techniques
Weak AI techniques can not be applied outside their intended domain
Weak AI has been successful in some domains, but often requires manual interaction with human experts to work
11/23/2018

5. Why use game AI?
Create more intelligent characters to improve game play
Allow the creation of single-player games with good opponents
Allow multi-player games to be played by one person
11/23/2018

6. Agents Smart entities are known as agents
Systems able to coordinate several agents as known as multi-agent systems
For performance reasons, the more agents in the game the simpler the complexity (time and space) of the AI
11/23/2018

7. Game AI
In game AI, results are important not the verisimilitude of the agent’s cognitive processing
Robust AI technology may not be needed if cleaver software engineering can be used to craft the illusion of intelligence
11/23/2018

8. Scripts Get keys out of pocket Put key in door Open door Get in car
Close door
Put key in ignition
Turn key to start car
11/23/2018

9. Searching and Routing
Least cost routing and searching systems use heuristics to simulate intuitive leaps of understanding that humans exhibit
Pathfinding is a variation of the routing problems
Some people equate faster search algorithms for with better problem solving capabilities\
Least-cost costs are preferred when a problem will be solved more than once
11/23/2018

10. A* Add root to queue of partial paths
Until queue is empty or goal is attained
If first queue element equals the goal then
do nothing
Else
remove the first queue element
add its children to the front of the queue of the partial paths
sort the queue of partial paths by distance traveled plus the estimate of distance to goal
remove redundant paths
If goal is attained then announce success
11/23/2018

11. A*
Makes use of both a cost measure and remaining distance underestimator
Removes redundant paths from the queue of partial paths
11/23/2018

12. A* Weaknesses Requires the use of a “natural” distance measure
Underestimator is a guess as best
Sorting takes time
Removing paths takes time
11/23/2018

13. Rules and Expert Systems
Knowledge bases are a substitute for institutional memory
Expert systems have been used quite successfully for to solve diagnostic and patter recognition problems
NPC behavior can be determined by expert systems, learning in these systems comes from acquiring more information about a situation rather than creating new rules
11/23/2018

14. Logic and Uncertainty
Need ways to accommodate incomplete and imprecise information
Fuzzy logic provides one way of dealing with these problems (set membership determined by probability membership function)
Usually requires numeric values to be assigned to degrees of uncertainty and numeric thresholds to determine when something is “likely” or not
11/23/2018

15. Natural Language Processing
Considered the holy grail of AI
The hard part is getting an NPC to understand the intent of a spoken question or statement, not just recognizing the words
Lots of heuristic tricks are used to make NLP seem like it is happening in games
Key word searches
Restricted (simplified) language grammars
Restricted vocabularies
11/23/2018

16. Neural Networks
Numerical approach used to simulate learning in AI systems
Good at learning to recognize desirable “patterns” in complex and imprecise data (give enough training and reinforcement)
Not good at explaining their decisions or reasoning processes
Very robust and can operate with reduced performance with missing network nodes
11/23/2018

17. Swarm Intelligence
Modeling behavior of groups made up of intelligent entities
Self-organization in game applications
Emergent (leaderless) coordination
Social insects/animals
Swarm systems do not have master controllers
The simple group entities are processing the same local data independently and arriving at similar decisions
11/23/2018

18. State of Game AI
Use scripted behaviors and A* pathfinding are examples of mature technologies found in many game AI systems
Some systems make use of decision trees or reinforcement learning, but it is some times hard to see where using advanced AI techniques has produced improved gameplay
AI technology may have the potential to speed up game production by speeding up design and experimentation during development
11/23/2018

19. AI Design Revolution
Several games like Black & White and the Sims are based on interactions with agents capable of modest amount of learning
These games have been widely received by the public
These games rely on AI established technologies but only recently has platform performance been sufficient to allow its use in real-time settings
11/23/2018

20. Designers vs AI Intelligent game characters behave autonomously
Designers need to control the behavior of NPC’s
Question: do we need both?
Presence of AI threatens designers’ authority
11/23/2018

21. Explicit Design
Designer’s implement their game vision in a top-down manner controlling every detail of the game
Common in game based on a single story line like Doom 3
With single-player scenarios there is little need for AI
NPC’s can be implemented using simple scripting techniques
11/23/2018

22. Implicit Design
Bottom-up design focused on using the interaction of AI and the game environment to create game play
There is no master story the game characters work together to create on like in Rollercoaster Tycoon
If NPC’s are intelligent, the designer’s only control over their behavior is by manipulating the environment
11/23/2018

23. Combining
Combining top-down and bottom-up design is an AI research problem
One solution is to alternate explicit control (set up the story) and implicit control (allow the player to play) like in GTA 3
During cut-scenes NPC behavior is disabled
During game regular play autonomous AI is free to do its thing
11/23/2018

24. Designer vs AI
The designer’s job is to craft the game from low level behaviors to the over all story line
Animating characters is part of this job
It is the AI’s responsibility to control the behavior of in-game characters to bring this vision to life
11/23/2018

25. Conflict
Occurs when the designer wants explicit control over an intelligent NPC (the AI must be turned off temporarily to accomplish this)
Occurs when the designer has a specific story line in mind (it is hard to get the NPC’s to force the player into the needed situation instead of doing what comes naturally)
It is important to specify particular story line twist early in design since resolving conflicts can require a lot programming work arounds
11/23/2018

26. AI in Game Programming In practice game AI controls every NPC:
Primitive behaviors (picking up items)
Movement (obstacle avoidance)
Decision making (decide what actions are needed and how to sequence them)
11/23/2018

27. AI Technique Benefits Provide elegant solutions for explicit control
Explicit requires over-riding system behaviors in certain situations
Provide technology to support implicit control efficiently
Implicit control requires when multiple operations are needed to achieve a goal
11/23/2018

28. Useful AI Techniques Motor control Pattern recognition Prediction
Approximation
Design patterns
Testing methodologies
11/23/2018

29. Game Value Added by AI Entertainment Believability
Tests skills of human players
Provides challenges with increasing difficulty
Evokes player emotions by adjusting environments
Believability
AI characters can improve immersivenes of games
Allow NPC’s to behave in plausible manners
11/23/2018