Now you see it… Now you don’t Introduction to Game AI

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 Sensing Reacting Locomotion 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

SPORE Agents Systems Content OH MY!

Recent Issues New systems and genres introduce new problems... Dynamic Path Planning Strategic Team-based AI Massively-Multiplayer AI Procedural 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 Applications Dynamic environments (Physics) Crowds (Pathfinding, animation) Agents (Planning, Learning) Genetic Algorithms

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 Procedural Content Generation & Management

Expressive Characters Memory Feelings Independent goals

Persistence Character Changes, World Changes Player 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/progress Characters that remember events Gossip? Grudges?

Wrapping up What we covered...

Game AI Then Big talk Plenty of proposed ideas Republic Black & White Fable Few successes (much debated) Halo AI Oblivion?

Game AI Now Gamasutra/Game Developer AI Programming Wisdom Journal of Game Development AIIDE

Game AI Tomorrow Maybe it’s you?