FAISystem Invalid Location

Development Programming & Scripting AI
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1

Hi! I’m taking a look to UE’s source code and step into FAISystem namespace. Within this namespace there’re some member variables:

	static const FRotator InvalidRotation = FRotator(FLT_MAX);
	static const FQuat InvalidOrientation = FQuat(FLT_MAX, FLT_MAX, FLT_MAX, FLT_MAX);
	static const FVector InvalidLocation = FVector(FLT_MAX);
	static const FVector InvalidDirection = FVector::ZeroVector; 
	static const float InvalidRange = -1.f;
	static const float InfiniteInterval = -FLT_MAX;
	static const uint32 InvalidUnsignedID = uint32(INDEX_NONE);

I’m curious about this const variables, I don’t understand what they do; their purpouse. In my ignorance I’m suposing they are some kind of initialization which represent something equivalent to a nullptr (regarding to funcionality). I’m thinking this for the use given to this const in other parts of the engine, e.g.:

struct FFocusKnowledge
{
	struct FFocusItem
	{
		TWeakObjectPtr<AActor> Actor;
		FVector Position;

		FFocusItem()
		{
			Actor = nullptr;
			Position = FAISystem::InvalidLocation;
		}
	};
	
	TArray<FFocusItem> Priorities;
};

As you can see, Position is set to FAISystem::InvalidLocation, why?. Could someone please elaborate further on this, I aprecciated in advanced!

2

As you can see, mostly all of them are structs or basic data types, that namespace is holding definitions for values that are invalid on that context.
The idea is that you have now variables that you know can’t be valid and those will pop up when something is not entirely correct, they will work so you can do validity checks when necessary. In this case they init everything as an invalid variable so each tick or data processing can override that value with something valid… BUT… if the processing fails for whatever reason or you try to use something that is not initialized you will se those variables and respond in time / avoid using them