Now you see it - Now you don’t

Intro to Game AI

Book Learnin’

University of Chicago– BA in General Studies– Masters work in AI & Information Systems

Northwestern University– PhD work in AI: Robotics & Video Games

Street Smarts

Game Design and Tuning Workshop Indie Game Jam/Experimental Gameplay

Workshop IGDA Education Committee

... and kickin’ it with developers, in general

What is AI?

Some terms

AI is...

a philosophy an abstraction a tool

Philosophy

People do things based on rough goals and sketchy plans – modifying their behavior when problems or opportunities arise.

Abstraction

Tool: Finite State Machine

start

end

Tool: Planner

state

goal

Tool: Agents

What is Game AI?

Some Context

Environment

Big projects, getting bigger Dynamic worlds/systems Time is still an issue

Problems

Pathfinding Sensing Reacting Expressing

People

Programmers Designers Players

Goals: Programmers

Intelligent, coherent, reactive behavior Consistent, accurate sensing

Goals: Designers

Extensible, flexible code Intuitive interface

Goals: Players

Coherent Believable Entertaining!

Fortress of Solitude: “If they worked properly,

they’d be tools - not toys”

Currently

Slow progress on – sensing– reacting

Problems crop up in – code– interface

State of the Art

Game AI Today

State of Game AI?

“State machines and hierarchical AIs. The simple rules-based finite- and fuzzy-state machines (FSMs and FuSMs) continue to be the tools of choice for developers, overshadowing more "academic" technologies such as neural networks and genetic algorithms.” – Woodcock 2001

Finite State Machines

Systems, Sub-systems and Sub-Sub systems– Proliferation of nodes = slower code– Changes in Agent design = chaos– Schizophrenic behavior = common– Difficult to debug

Rule-Based Systems

Special Cases made easy– Scripting can be tedious– Debugging can be difficult– Flexibility? Extensibility?

Hierarchical AI

Commanders, Middlemen, Drones– Lots of reasoning– Lots of inter-level communication– What does the user see?

– Best in strategy contexts?

Other approaches?

Black and White, Creatures, The Sims– Neural Net– Learning/Reinforcement

– Transparency? (why?)– Transitions? (how?)

Other approaches?

Thief I & II– Complex Sensing– Brooksian, Distributed AI

– Scalability? (how many brains?)– Intuitiveness? (which brain?)

More Recently

Optimizations– Blackboard Systems (NOLF 2)

Broadening scope– Diagnostics (DX 2)– Expressive Characters (HL 2)

Paul Eckman

Recent Issues

New systems and genres introduce new problems... – Dynamic Path Planning– Strategic Team-based AI – Massively-Multiplayer AI

Next-Generation AI?

Will new technology engender new and improved techniques?

Will new problems have clear, simple solutions?

What about Middleware?

Game AI In a Box?

Middleware

Animation & Locomotion Control

Middleware

Behavior Control Systems

Middleware

Structural Organization/Interface

Middleware

Middleware

Hard to get developers to use it Not clear what value it provides

– are they the right abstractions?– will the tools be flexible enough?

AI seems specific to game genre/content

Looking Forward

Juicy AI Problems

Dynamic Game Adjustment

Difficulty Pacing Story Characters

– The future looks... complicated!

Natural Language Generation

Context-aware conversations Common-sense responses Dynamic phrase generation

Expressive Characters

Memory Feelings Independent goals

Persistence

Character Changes, World Changes– Chess Examples

Persistence

“There are no character classes in Project Ego, only personality styles that evolve according to the decisions you make. Your character will age as time progresses, and the actions you take put an idiosyncratic spin on his or her appearance. Early wounds will show up later as scars. Lethargy will manifest as a little extra blubber around your middle, and anaerobic exercise will show up in the form of Olympian muscles.

Even more important than your looks, your reputation will depend on the kind of life you lead. The incredible freedom of gameplay allows you to pursue every occupation from dashing hero to indolent bum to mischievous cutpurse.”

How would you build “Fable”?

Persistent beliefs about the main character Clear presentation of change/progress Characters that remember events Gossip? Grudges?

Wrapping up

What we covered...

Game AI Then

Big talk up to about 2001 Plenty of proposed ideas tanked/ignored

– Republic– Black & White

Game AI Now

Gamasutra/Game Developer AI Programming Wisdom

Game AI Tomorrow

Look to next round of games for ideas? AI ‘04 – workshop in the works GDC ’04 – hopefully some tidbits

Contact

hunicke@cs.northwestern.edu