Blueprint Default Values Diverge from C++ Class Definitions

Development Programming & Scripting C++
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1

Howdy y’all, I’m experiencing an issue in Unreal Engine 5.3 (although I suspect it may be an issue in older versions as well).

I have a SMagicProjectile class (derived from parent class SProjectile) with a SphereComponent root. SMagicProjectile initializes with specific collision responses (see code). When I make a blueprint derived from SMagicProjectile, the Overlap collision settings shows correctly – but are considered non-default values (indicated by an arrow icon). Resetting those values changes the values from overlap (the correct value as defined in the C++ code) to block.

Interestingly, moving the Overlap collision response setting to the BeginPlay method makes the arrow disappear after recompiling. I’m looking for help to understand:

  1. Why is this happening?
  2. How can I fix this without relocating the collision setting code to the BeginPlay method?

Here is are relevant pieces of code below:

SProjectile.cpp (parent class of SMagicProjectile):

#include "SProjectile.h"

#include "GameFramework/ProjectileMovementComponent.h"
#include "Particles/ParticleSystemComponent.h"
#include <Components/SphereComponent.h>

ASProjectile::ASProjectile(float InitialSpeed, float InitialGravityScale)
{
	InitializeComponents();
	MovementComp->InitialSpeed = InitialSpeed;
	MovementComp->ProjectileGravityScale = InitialGravityScale;
}

void ASProjectile::InitializeComponents()
{
	PrimaryActorTick.bCanEverTick = true;
	PrimaryActorTick.bCanEverTick = true;
	SphereComp = CreateDefaultSubobject<USphereComponent>("SphereComp");
	RootComponent = SphereComp;
	EffectComp = CreateDefaultSubobject<UParticleSystemComponent>("EffectComp");
	EffectComp->SetupAttachment(SphereComp);
	MovementComp = CreateDefaultSubobject<UProjectileMovementComponent>("MovementComp");
}

ASProjectile::ASProjectile()
{
	InitializeComponents();
}

SMagicProjectile.cpp:


#include "SMagicProjectile.h"

#include "GameFramework/ProjectileMovementComponent.h"
#include "Particles/ParticleSystemComponent.h"
#include <Components/SphereComponent.h>

ASMagicProjectile::ASMagicProjectile() : ASProjectile(2000.0f, 0.0f)
{
	SphereComp->SetCollisionObjectType(ECC_WorldDynamic);
	SphereComp->SetCollisionEnabled(ECollisionEnabled::QueryAndPhysics);
	SphereComp->SetCollisionResponseToChannel(ECC_WorldDynamic, ECR_Block);
	SphereComp->SetCollisionResponseToChannel(ECC_WorldStatic, ECR_Block);
	SphereComp->SetCollisionResponseToChannel(ECC_Pawn, ECR_Overlap);
}
2

You are trying to alter inherited values hence why in begin play it works as expected so either define a property that can be edited or super the onconstruction or create a method that you can call to set values

3

Thanks for the suggestion here! To test this, I had moved the SetCollisionObjectType (and all other collision settings) into the SProjectile class (rather than MagicProjectile`). I still encounter the same issue.

To make it even simpler, I even created a Blueprint based off of SProjectile class and I still see the same behavior.

If the problem is caused by inheritance, shouldn’t that change resolve the issue?

4

yeah but because in the parent the values are set in the constructor it will require overriding it in the onconstruction or constructor without viewing it more closely, but i would say have a quick look at some c++ collision inheritance vids just to see what I mean