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OnBeginOverlap from c++ not working

I found several posts here about it, but I cannot find what I'm missing in this case, so maybe someone else here is able to see that


 class LASTFANTASY_API ACombatMode : public AStaticMeshActor
     void Enable();
     void BlurEnvironment();
         void OnOverlapBegin(UPrimitiveComponent* OverlappedComp, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult);
     UPROPERTY(BlueprintReadWrite, VisibleAnywhere, Category = "Trigger")
         UBoxComponent* TriggerBox;        


     TriggerBox = CreateDefaultSubobject<UBoxComponent>(TEXT("TriggerBox"));
     TriggerBox->AttachToComponent(GetRootComponent(), FAttachmentTransformRules::KeepRelativeTransform);
     TriggerBox->bGenerateOverlapEvents = true;
     TriggerBox->OnComponentBeginOverlap.AddDynamic(this, &ACombatMode::OnOverlapBegin);    
 void ACombatMode::OnOverlapBegin(UPrimitiveComponent* OverlappedComp, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
 void ACombatMode::Enable()
     //GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, TEXT("This is an on screen message!"));
     debug(TEXT("EnableCombat Mode")); // macro for addOnScreenDebugMessage
 void ACombatMode::BlurEnvironment()

I don't see the debug output here. What am I missing in this case?

Product Version: UE 4.13
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asked Oct 07 '16 at 06:09 AM in C++ Programming

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avatar image trojanfoe Oct 07 '16 at 01:48 PM

Open the console (~ or ` key) while in play mode and type "show collision" to show the collision bounds. Check if there is a collision bounds as you don't set the size of the box component. Also not sure if you need to turn off simulate physics or not as you might be generating collisions and not triggering.

avatar image xhallix Oct 07 '16 at 02:04 PM

Hi and Thanks for the reply. I adjusted the size of the Trigger Box on the component blueprints. When using eventonActoroverlap for the same component in their bp, everything woks fine. So I assume I missed something in the Code

avatar image kevin_g Oct 07 '16 at 07:21 PM

A couple things I would try for debugging this:

  1. Add debug output to Combat::ACombatMode() to verify it's getting called properly

  2. 'show collision' while in gameplay to check if the box is where you expect it to be, and if it ever overlaps anything you would expect to trigger overlap events.

  3. Check if whatever you're checking overlap with also has overlap enabled with overlap channels also enabled.

  4. Double check that UBoxComponent has the expected default overlap channels when spawned under 'Collision' settings. (Spawn it in Blueprints and take a look at it there).

avatar image xhallix Oct 09 '16 at 07:48 AM

All this checks seems to be correct, because it works in the bp of the same component :(

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4 answers: sort voted first

For those who are having the same issue, here is what I figured out

If you create a blueprint based, on a c++ class and later in that code (while the bp has already been created) you are adding "AddDynamic"-Bindings, you may have to delete and recreate the bp after compile, because the binding seems not to be recognized when the BP has created before

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answered Oct 09 '16 at 07:59 AM

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avatar image Unzkilled Sep 14 '17 at 01:14 PM

You are a [redacted] genius. Solved my problem too!

avatar image dustycoder Feb 28 '19 at 03:26 PM

I have been trying to figure this out for weeks, off and on, I can't believe this is the solution and still in 4.21. Insane, but thank you.

avatar image REDVIL44 May 18 '19 at 10:55 AM

Thanks man. This solved my issue. They should fix this in the engine.

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Since you are using AddDynamic Binding in constructor which is called initially.You have to do in begin play.

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answered Jan 28 '18 at 06:38 AM

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Do you need to actually set a RootComponent? (I also ask this to the community, not rhetorically!)

In my C++ actors, following from examples, I've always called CreateDefaultSubobject, like you have. Then with one of them, set it as the RootComponent. So in your case, something like:

 TriggerBox = CreateDefaultSubobject<UBoxComponent>( TEXT( "TriggerBox" ) );
 RootComponent = TriggerBox;

I'm wondering if there must be a RootComponent set, before you can then call AttachToComponent( GetRootComponent()..., lest that return a NULL/nullptr?

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answered Oct 07 '16 at 09:44 AM

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avatar image trojanfoe Oct 07 '16 at 10:00 AM

Normally you would, yes, but the OP is using AStaticMeshActor as his base class (for some reason) which I assume has a UStaticMeshComponent added by default and set as the root component.

avatar image Jawdy Oct 07 '16 at 10:18 AM

Thanks! I looked at some of my code, to try and help, and thought "Hmm, do I need to do this?" But yup, I still do, heh.

avatar image xhallix Oct 07 '16 at 11:17 AM

hm but this doesn't answer my question in any case :(

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You've told the actor to collide and you've told the component to trigger overlaps and you've tied your respondent method to the overlap event; but what you've missed is telling the engine/component how to decide if the overlap has been triggered. Specifically, you need to tell the component what other objects should trigger collisions or overlaps and which should be ignored. This is done in UE4 by assigning the component a collision profile and/or by setting specific responses to available collision channels.

In your component setup you'll want to add something like this:

 //setting a collision profile; each profile has default behaviors defined per channel
 TriggerBox ->SetCollisionProfileName(UCollisionProfile::NoCollision_ProfileName);
 //setting collision response type
 TriggerBox ->BodyInstance.SetCollisionEnabled(ECollisionEnabled::QueryOnly);
 //setting collision response by specific channel
 //you can override individual channel responses within your existing profile, or set specific responses for every
 //available channel in your game

 //this first line strips any preset collision responses and sets the component to ignore all
 TriggerBox ->BodyInstance.SetResponseToAllChannels(ECR_Ignore);

 //you can set individual response types for the channels you want; ECR_Overlap, ECR_Block, or ECR_Ignore
 //in this case all are set to trigger overlaps
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_WorldStatic, ECR_Overlap);
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_WorldDynamic, ECR_Overlap);
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_Pawn, ECR_Overlap);
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_PhysicsBody, ECR_Overlap);
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_Vehicle, ECR_Overlap);
 TriggerBox ->BodyInstance.SetResponseToChannel(ECC_Destructible, ECR_Overlap);

You can build the component's channel response to respond differently to different channels, as well as create your own custom channels and collision profiles.

You can also set these values in the editor within the details panel of your object, under Collision and the Collision Presets panel.

For more details see:




Default collision channels and response types are defined in 'Runtime/Engine/Classes/Engine/EngineTypes.h'; see lines 553 and 743.

UCollisionProfiles are defined in 'Runtime/Engine/Classes/Engine/CollisionProfile.h'

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answered Oct 10 '16 at 04:35 AM

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avatar image xhallix Oct 10 '16 at 05:55 AM

Thanks but in my case it was just simply recreating the assset whjch helps

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