GOAP Extensions

We use GOAP for our AI in Academia. It’s working well for us so far. New behaviour can be easily added and AI glitches can be easily fixed. But I’ve had problems with it as well. One of them which needed fixing is duplicate actions.

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We use GOAP for our AI in Academia. It’s working well for us so far. New behaviour can be easily added and AI glitches can be easily fixed. But I’ve had problems with it as well. One of them which needed fixing is duplicate actions.

We have different classes of characters in the game. We have students, teachers, workers, cooks, nurses, and janitors (more are coming). Each of them have different set of actions but most of the time, they also have a common set of actions. For example, eating. If I fix the eating behavior in students, that means that I have to also apply the same fix to the other classes. This is maintenance nightmare. A character class could become broken if I just happen to forget a certain fix. Applying a fix to each of the classes is tedious, too.

GOAP Actions Refactoring

I needed a way to refactor GOAP actions in such that I could just edit one set of actions and it will be applied to all the character classes. Thus, I introduced “extensions” to our GOAP framework.

GoapExtensions

An extension is basically a reference to another GOAP data set. During parsing of this data, the system adds all the actions found in the extension. An extension can also have a set of preconditions. These preconditions are added to all the actions in the extension. For example, from the image above, the NeedsBehaviour extension will only be executed if HasRequestedTreatment = false.

The refactored actions that pertains to “needs” are now placed in its separate GOAP data set:

NeedsBehaviour

The specific GOAP data for each character class can simply reference this “needs” data to be able to execute such actions. I only need to fix this “needs” GOAP data if I have to fix a “needs” related behavior. No need to apply separate fixes to each character class.

This feature turned out to be very useful. Every time there’s a new set of behaviour that could be reused, I put them in a separate GOAP data. The character class that requires it could just add this new data as an extension. For example, for now, only students can use computers. So I made a separate GOAP data called “ComputerLabBehaviour” and added it as extension to the student’s GOAP data. Later on, if we decide that teachers could also use computers, I can simply add the “ComputerLabBehaviour” data as extension to the teacher’s GOAP data.

Behaviours
Our current set of behaviours

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