now you see it… now you don’t

Now you see it… Now you don’t

Introduction to Game AI

What is AI?

Some terms

AI is...

a philosophyan abstractiona 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 biggerDynamic worlds/systemsTime is still an issue

Problems

SensingReactingLocomotionExpressing

People

ProgrammersDesignersPlayers

Goals: Programmers

Intelligent, coherent, reactive behavior Consistent, accurate sensing

Goals: Designers

Extensible, flexible codeIntuitive interface

Goals: Players

CoherentBelievableEntertaining!

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 systemsProliferation of nodes = slower codeChanges in Agent design = chaosSchizophrenic behavior = commonDifficult to debug

Rule-Based Systems

Special Cases made easyScripting can be tediousDebugging can be difficultFlexibility? Extensibility?

Hierarchical AI

Commanders, Middlemen, DronesLots of reasoningLots of inter-level communicationWhat does the user see?

Best in strategy contexts?

Other approaches?

Black and White, Creatures, The SimsNeural NetLearning/Reinforcement

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

Other approaches?

Thief I & IIComplex SensingBrooksian, Distributed AI

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

More Recently

OptimizationsBlackboard Systems (NOLF 2)

Broadening scopeDiagnostics (DX 2)Expressive Characters (HL 2)

Paul Eckman

SPORE

AgentsSystemsContent

OH MY!

Recent Issues

New systems and genres introduce new problems... Dynamic Path PlanningStrategic Team-based AI Massively-Multiplayer AIProcedural Animation/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

Logic

Middleware

Workflow integration

Interface

Editors

Middleware

Prove it!AI Implant: Unreal, various games

Targeted ApplicationsDynamic environments (Physics)Crowds (Pathfinding, animation)Agents (Planning, Learning)

Genetic Algorithms

Looking Forward

Juicy AI Problems

Dynamic Game Adjustment

DifficultyPacingStoryCharacters

The future looks... complicated!

Natural Language Generation

Context-aware conversationsCommon-sense responsesDynamic phrase generationProcedural Content Generation &

Management

Expressive Characters

MemoryFeelingsIndependent goals

Persistence

Character Changes, World ChangesPlayer is on stage

Theory

“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.”

Reality?

“Most quests fall into typical RPG trappings … to make them more interesting, Fable allows you to 'boast' at the Boasting platform. There are usually only four or five pre-determined boasts available for any one quest, and you can't mix and match… Again, if you didn't know about it before, you're better off than those of us who expected the boasting to be more user-controlled….

And even if you boast like a maniac, you probably won't have too hard a time accomplishing your task because Fable is oddly easy... Part of that is due to the game's uninspired enemy A.I; bad guys pretty much just beeline for you if you're within range. The diversity is thin, featuring basic variations on only about a dozen types of monsters. You'll fight a lot of the same things over and over again.”

Design vs. AI

“Perhaps the biggest question about Fable is its replay value. There's obviously no multiplayer here, so it all boils down to how much the story branches based on your alignment. The answer, unfortunately, is very little.

While there are a few different ending sequences based on a combination of your alignment and one very large decision you make towards the end, you won't need to play through the whole thing again to see 'em because the game actually allows you to change alignment mid-stream by simply going to the good or evil church and making donations. Whoops! Sort of takes the value out of making bad decisions when you can pay for instant repentance, eh?”

How would you build it?

Persistent beliefs about the main character

Clear presentation of change/progressCharacters that remember eventsGossip?Grudges?

Wrapping up

What we covered...

Game AI Then

Big talkPlenty of proposed ideas

RepublicBlack & WhiteFable

Few successes (much debated)Halo AIOblivion?

Game AI Now

Gamasutra/Game DeveloperAI Programming WisdomJournal of Game DevelopmentAIIDE

Game AI Tomorrow

Maybe it’s you?