The first session at GDC's AI Summit features a case study of recent games. This post contains all the references from my presentation about KILLZONE 2's multiplayer bots, and specifically their AI strategy. The project was done under the expert supervision and guidance of Remco Straatman (Lead AI Programmer) along with Tim Verweij, who also established the architecture as part of his thesis. Here's the presentation itself:
On the AI Strategy for KILLZONE 2's Bots Alex J. Champandard, Remco Straatman, Tim Verweij. Download FILE
The rest of this post contains all the references from the talk itself, including work and presentations by Arjen Beij (Senior AI Programmer), Michiel van der Leeuw (Technical Director), and William van der Sterren. Most of these references are available freely, either as a public download or for AiGameDev.com Insiders (free registration). If you'd like to go into more details, see the the full video recordings as part of the Premium Area.
Individual AI
For details about the combat AI for individual humanoids based on KILLZONE 1's technology, see the talk from the Game Developer's Conference 2005:
Procedural Combat Tactics (Paper) Remco Straatman, Arjen Beij, William van der Sterren Download PDF
Procedural Combat Tactics (Slides) Remco Straatman, Arjen Beij, William van der Sterren Download PDF
For details about the AI as it has evolved on the PS3 and SPU, see these extracts of the talk by Michiel van der Leeuw:
- Where Did That Enemy Go? Threat Prediction and Reasoning
- Not in My Line of Fire! Sensible Combat Behaviors using SPU Jobs
- Waypoint Cover Maps and Efficient Raycasts on PS3
These are Insider articles and include a video of the technology.
Architecture & Planner
For details of the overall architecture, see Remco Straatman's part of the presentation at the Paris Game AI Conference 2009, which is based on Tim Verweij's thesis work:
Killzone 2 Multiplayer Bots Remco Straatman, Tim Verweij, Alex Champandard Download PPT or PDF
Terrain Reasoning & Pathfinding
For more information about the processing and analysis of terrain, then finding a balance between automation and manual annotations, see this AiGameDev.com report with Kevin Dill, Sergio Garces, William van der Sterren and Paul Tozour.
- Terrain Annotations: From Designer Hints to Automated Pre-processing
- Terrain Representation: AI Hints and Spatial Data-structures (Insider)
- Terrain Analysis & Reasoning (Premium)
The automatic area generation is based on a clustering algorithm. William van der Sterren's work is the best reference on the subject. There's also an implementation in the AiGameDev.com Sandbox that you can see in action here:
- Terrain Area Generation from 2D Grids and Waypoint Graphs
- Automated Terrain Analysis with William van der Sterren (Premium)
The squad pathfinding is derived from my master's thesis, though with some improvements since this publication:
Realistic Autonomous Navigation in Dynamic Environments Alex J. Champandard, 2002. Download FILE (1.4 Mb)
The algorithm is essentially a hybrid combination of Dijkstra and Bellman-Ford-Moore.
Strategy
As a reference for the squad and objective assignment logic, see this talk at GDC 2008 by Damian Isla:
Building a Better Battle: The Halo 3 AI Objectives System Damian Isla, 2008. Download ZIP Archive
For more information how different that was in KILLZONE 2, see the details in the recording from the Paris Game AI Conference 2009:
Summary
In this case and in general, strategy is more than the sum of its parts. Individual components of the system are relatively straightforward, well documented, and easy enough to implement. However, its their combination that make the overall result much more dynamic and involving to players.
If you have any similar experiences working on the AI strategy in your game, or have any questions about the technology in KILLZONE 2, don't hesitate to post a comment below.
