Once inside the IDE the code was't too difficult to rewrite. I wrote two functions that accept a few arguments that just replicate what the Blueprint was already doing. I included the KismetMathLibrary in the .cpp file to utilize it's RLerp function.

MyBlueprintFunctionLibrary.h

#pragma once

#include "CoreMinimal.h"
#include "Kismet/BlueprintFunctionLibrary.h"
#include "MyBlueprintFunctionLibrary.generated.h"

/**
 * 
 */
UCLASS()
class MYPROJECT_API UMyBlueprintFunctionLibrary : public UBlueprintFunctionLibrary
{
	GENERATED_BODY()

	// Static functions do not require a target and they will appear in Blueprints when Context Sensitive is checked
	UFUNCTION(BlueprintCallable, BlueprintPure, Category = "Door Functions")
	static bool IsActorInFront(FVector ActorLocation, FVector OtherActorLocation, FRotator OtherActorRotation);

	UFUNCTION(BlueprintCallable, BlueprintPure, Category = "Door Functions")
	static FRotator GetRotateValue(FRotator ActorRotation, float Alpha, bool OpenDirection, float RotateDegrees);
};

MyBlueprintFunctionLibrary.cpp

#include "MyBlueprintFunctionLibrary.h"
#include "Kismet/KismetMathLibrary.h"

bool UMyBlueprintFunctionLibrary::IsActorInFront(FVector ActorLocation, FVector OtherActorLocation, FRotator OtherActorRotation)
{
	FVector NewLocation = ActorLocation - OtherActorLocation;
	FVector UnrotatedVector = OtherActorRotation.UnrotateVector(NewLocation);
	
	return UnrotatedVector.X > 0 ? true : false;
}

FRotator UMyBlueprintFunctionLibrary::GetRotateValue(FRotator ActorRotation, float Alpha, bool OpenDirection, float RotateDegrees)
{
	float Direction = OpenDirection ? RotateDegrees : -RotateDegrees;
	FRotator NewRotation = FRotator(0.0f, Direction, 0.0f);
	FRotator FinalRotation = UKismetMathLibrary::RLerp(ActorRotation, NewRotation, Alpha, true);

	return FinalRotation;
}

After writing these two functions and recompiling I was able to add them to the BP_Door Blueprint. Next, I added a new float variable to BP_Door called RotateDegrees and defaulted the value to 90 that will be passed to the GetRotateValue function. These two library functions are pretty Door Blueprint specific, so they're not very re-usable, but for this simple exercise it's fine, we're just having fun.

C++ Posts

Creating a Blueprint Function Library is a Fun Way to Get Started with C++ Inside UE5