We are contuining our series of interviews around Civilization III, with Soren Johnson, the AI Programmer on Civ III. It's a short one, with fewer than usual questions, but it's all about AI. We hope that you find it interesting!

Apolyton: Does the AI make decisions on large scale, small scale, or both?
Soren Johnson: The AI makes decisions on many different levels. A leader AI keeps track of high-level concepts, like whether enough science is being generated or which civ is the biggest threat. A city AI decides which units to build for that area of the world and how to manage the city itself. The unit AI is itself split into multiple levels, first determining an ideal destination and then calculating the best possible path.

Furthermore, the different AI levels communicate between each other. For example, the unit AI controlling a tank might ask the leader AI which enemy city would be best to attack. After receiving a response, the unit AI would determine its own best path to the destination. Thus, the AI is able to organize a large group of units while keeping the discrete game decisions at a lower level.

Apolyton: Is there any kind of customization in the way the AI works?
Soren Johnson: Each leader in Civ III has his or her own personality. An extreme example would be a pacifist ruler favoring democracy and cultural improvements or an aggressive ruler preferring despotism and offensive ground units. These personalities are fully customizable through the editor, so creating AI’s with different priorities is quite easy.

The AI personalities were included to create memorable opponents, liberally based on the historical record. Thus, Gandhi is peace-loving, Elizabeth is cautious, and Shaka is blood-thirsty. In other words, the emphasis was on crafting a fun, engaging experience for the user instead of building the “perfect” AI. The mod community, however, will have the opportunity to create better AI’s by experimenting with these variables. Further, users who dislike preset personalities can turn them off altogether and let the AI adapt to its environment from a blank slate.

Apolyton: Do the number of civilizations in the game affect the AI? Will the AI give you more trouble with 6 civilizations than with 16?
Soren Johnson: The number of civilizations in a game definitely affects AI behavior. However, this fact does not necessarily mean that the AI’s on a world with fewer civs will be more aggressive. The AI adapts to its environment, and the number of civilizations in the world is simply one of the many factors used for decision-making. For example, if a game was started on a Huge map with only 6 civs, the AI might emphasize expansion to take advantage of the extra space available.

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