Arctic Edge devlog #3: enemy AI (part I)

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This is the third post on a series about the development of Arctic Edge, a stealth-action game I’m working on. If you missed the previous post click here or here for the whole series.

Listening to the player

When I started thinking about how could the enemies “listen” to the player while running I went for the quickest, simpler solution: Detect the collision with the player inside a circle of r radius around the enemy. If the player is running alert the enemy.

That definitely works, but only allows me to detect the player moving, nothing else. If I want to detect the player shooting I will have to add some other conditional. And the same for other noise producing actions. Besides being a messy and limited solution, it’s also kinda lazy.

To fix this I came up with something that seems to be working quite well. I’ve created a new object: the noise object. The enemies detect instances of this object and act accordingly changing the estate of the enemy.

The noise object is very simple. It has two important variables: a radius and a duration. Every time the object is instantiated (in position xy, for example wherever the player took his last step), the object grows linearly until it gets to the desired radius and it does so in the defined time (duration). After reaching the full size, the object destroys itself.

The noise object in action. It’s a bit difficult to see due to the speed and quality of the video but each noise object appears as a white circle, grows to it’s maximum size and disappears.
The circle won’t be shown in game, it’s only for debugging purposes.

This approach is very flexible and helps me in many ways. For example, when the player is running I can create the noise object only when I’m actually playing the step sound (not implemented yet, but still). It also allows me to create different intensity (radius and duration) steps depending on the material the players steps on. This can also be applied to the gunshots. Not to mention that I’m not limited by the user position to create this noises. I could make an explosion that alerts everyone around or throw a rock away from me to distract an enemy that is approaching.

I’m aware that I’m not discovering anything new but it’s been fun to come up with this solution and prototype it into the game.

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