The Halo 2 AI In 10 Minutes or Less Damián Isla Bungie Studios

Halo First person shooter for XBox Interesting sci-fi world Lots to do (combat, exploration, vehicles, weapons) Lots of decisions to make Slower-paced More strategic in nature?

The AI Single-player campaign only (no multiplayer) Character-based Enemies Large variety Clear behavioral patterns for the player to learn and exploit 4 - 30 second lifespans Allies Not terribly effective “Kid brothers” ~10 seconds or ~30 minutes

The “I” in “AI” Behave Strongly agent-based approach Perception and world-modeling Each AI maintains mental world model Internal mental object-state updated according to perceivability via the “senses” (e.g., line of sight, sound events, etc.) Perception sharing (via explicit communication) Behavior Take cover when taking damage Uncover hidden enemies Use vehicles when appropriate Joint behaviors Skills Use weapons appropriately Drive vehicles Navigate the environment Strongly agent-based approach “Strategy” controlled through scripting Behave

Behavior Decision-making: Behavior DAG (HFSM) Behavior: a program that takes temporary control of the actor in order to get something done. Good Intuitive Modular Scalable (more IS better) Bad Memory is hard Debugging is hard Never really that simple

An ethological interlude… Baerends, The Functional Organization of Behavior, 1976

What about Reasoning and Planning? Spatial Reasoning Firing point selection Path-planning A* Dynamic obstacle interaction … but no concept-reasoning or action-planning

So in the end… Second-to-second decision-making Reactive in nature Closer to A-Life than classical AI Closer to animal than to human intelligence