Artificial Intelligence: Games

Influence mapping is another one of those things we take for granted when playing a strategy simulator from Blizzardª, or Bungieª. Influence mapping is basically a way of determining influence of units in specific or general areas. Make any sense? No? Good.

The American Herritage Dictionary defines influence as, "A power affecting a person, thing, or course of events, especially one that operates without any direct or apparent effort." Mapping, is defined as, "A representation, usually on a plane surface, of a region of the earth or heavens." So, influence mapping is basically, "A representation of the amount of power a person (or thing) has in a particular area." Still doesn't make any sense? Ok, perhaps this will help. Let's take a look at the problem before we get into the solution.

Assume that the purple spheres are a human player's troops, and the red/orange one is the computer. Let's say now, that the computer soldier wanted to get from point A, to point B. These should help you to understand how the computer would store data about this situation.

Fig A


Fig B	Fig C

Figure A is a combination of what the player sees, and what the computer sees. That should make it easier for you to see the relation between the two. Figures B and C are the views split up. Figure B is the battlefield from a different orientation, and Figure C is a matrix. Computers often use things like matrices to store data about objects, like a terrain. In this matrix, the negative numbers represent the purple troops(enemy), and the positive ones the red/orange(friendly). For convinence, point A is red in the matrix, and point B is blue. If conventional methods were used, the computer soldier wanting to move to point B would note that the value at that location in the matrix was 0, meaning it was unoccupied -- safe. However, upon examination by a human, it can be determined that this would be a horrible move. The troop would be surrounded! This is where influence mapping comes into play.

The goal of influence mapping is to show how much power a particular player has in a particular area. As always with AI, it's a mathematical operation. What we want to do, is change the values of each place in the matrix based on its neighbors. For instance, take a look at this matrix, and then how it changes after we perform the simple operation the first time.

In case you couldn't tell, if the value was originally negative in a particular square, we subtracted one from its neighbors. If the value was positive, we added one. If the value was zero, we left it alone. It seems simple now, but it gets complicated quick.

This method is one of the methods used to produce real-time statistics on troops, and stuff like that, commonly used in games. Sources : "Influence Mapping" thread

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