Source Code

This article looks into the publicly available SDK for Half-Life 1, analyzing the various aspects of the AI such as the task scheduling system, its state-machine like implementation, and the sensory system. Even ten years later, looking into the codebase of this critically acclaimed game is a great way to learn about designing simple but effective AI systems.

Call of Duty 4: Modern Warfare received high praises from the community here. Admittedly, the AI in the game doesn’t necessarily shine for technical reasons, but it’s wonderfully put together within the whole story, and has arguably become one of the best examples of scripted level design. This article provides an overview of the development tools inside the SDK, explains how the AI logic is structured, and then dig deeper into the level scripts to show how it was put together.

Quake 3 Arena makes for interesting study as it is fully open-source (except the tools), and the code contains a feature-complete death-match bot AI written in plain-old C; it’s surprisingly easy to follow when you understand the syntax of the language. As well as a simple goal architecture, you’ll find some solid technology in the Area Awareness System (AAS) and the pathfinding solution too (a.k.a. routing).

This article looks into the latest SDK behind F.E.A.R., the hit first-person shooter acclaimed for its artificial intelligence. A majority of the AI code is available as part of the game source, and notably its famous STRIPS planner written by Jeff Orkin.