How to make percentage based spawning system

[Player_003]

How to make percentage based spawning system i know there is select option and than you can make random integer in range but is there any way to make like 20% spawning change of one enemy and 16% of spawning other… and like that

[Everynone]

@Player_003

20% spawning change of one enemy and 16% of spawning other… and like that

What’s the actual scope? Because you could set up 5 cascading Branches and carry on with the dev. How scalable must this be?

[Player_003]

it will be at least 10 enemies and i dont want to have 10 branches one after the other

[Everynone]

Experiment with curves, see if it works for you:

This one would favour lower tier enemies in a 0-10 range (11 choices):

This way there’s no need to punch in any values, you adjust the curve instead; and can use a different curve for other difficulties, for example.

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There is no single node that does what you want to do, you’d need to write a bunch of script anyway.

[KiiroiSenko]

If you are willing to write about 30-40 lines of code you can get a blueprint node for this :
1 - From the editor’s Tools menu choose “New C++ class”
2 - In the all classes tab look for BluePrintFunctionLibrary and select it.
3 - Press next and then create class. Two files will be created in the directory shown in the last step before pressing create class
4 - Open the file that ends with “.h”
5 - copy the code below and paste under the line with the words “GENERATED_BODY”
6 - Compile your project

public:
	UFUNCTION(BlueprintCallable, BlueprintPure, Category = "Random")
	static TSubclassOf<AActor> GetRandomActor(const TMap<TSubclassOf<AActor>, float>& ActorMap)
	{
		const float RandomValue  = FMath::FRandRange(0.f, 100.f);
		float CumulativePercent  = 0.f;
#if WITH_EDITOR
		TSubclassOf<AActor> SelectedActor = nullptr;
		for (const auto& Element : ActorMap)
		{
			checkf(Element.Value >= 0 , TEXT("Percentages must be positive when using Get Random Actor node!"));
			CumulativePercent += Element.Value;
			if (RandomValue <= CumulativePercent
				&& SelectedActor == nullptr)
			{
				SelectedActor = Element.Key;
			}
		}
		checkf(FMath::IsNearlyEqual(CumulativePercent, 100.f, UE_KINDA_SMALL_NUMBER), TEXT("Sum of the percentages must be 100 when using Get Random Actor node!"));
		return SelectedActor;
#else
		for (const auto& Element : ActorMap)
		{
			CumulativePercent += Element.Value;
			if (RandomValue <= CumulativePercent)
			{
				return Element.Key;
			}
		}
		return ActorMap.Array().Last().Key;
#endif
	}

This will give you a node like this:

Key is the actor you want to spawn and value is the spawn chance.
If you give any negative value or your percentages don’t add up to 100 and you are playing with editor this will crash your game and you will see why it crashed (either negative value or the sum) in the crash log. Outside of editor builds you just get the last actor in the map if you don’t give it correct values. An empty map will crash your game (or maybe it doesn’t f^^; check this one yourself).

Sorry if you wanted a BP exclusive answer >.<;

[KiiroiSenko]

Ok nevermind, you don’t even need C++. Made the same thing in blueprint.

Doesn’t have the safety checks of the C++ one though. I’m not sure if you can do that in BP.

[Player_003]

thank you i will probably do it in c++ when i get time because im busy these days