Unreal Engine C++ Fundamentals – FTimerHandle & Timers

By | Development, Tutorial, Unreal | No Comments

Hey guys,

We are bouncing back to C++ Fundamentals this time looking at FTimerHandle and  Timers in general by messing around with our props.

Additionally you can always find the sample project on our GitHub page.

Timers ?! What are they ?

Timers allow us to trigger events based on elapsed time in the form of creating asynchronous callbacks to specific function pointers.

Plain English: we light a fuse, let it burn down, something explodes !

How do we make these magical exploding clocks ?

Well let’s take a look at some code as these things are pretty easy to understand.


FTimerHandle TriggerDestroyTimerHandle;

void TriggerDestroy();


GetWorld()->GetTimerManager().SetTimer(TriggerDestroyTimerHandle, this, &ADestructibleProp::TriggerDestroy, 5.f, true);

void ADestructibleProp::TriggerDestroy()
  // do stuff

So as you can see the implementation is pretty easy to understand.

  • We are creating a timer from our Time Manager object.
  • We are then registering this call back to use our Timer Handle.
  • Then we assign a callback method to be triggered at the end of our countdown.
  • Then finally we set that the countdown duration is 5 seconds.

Excellent ! Let’s blow some things up.

Timers can also be used to trigger modifications to specific values every so often. In this case we are going to simulate a fuse that will count down every second before it triggers an event.

First we are going to call the timer as we did previously, except this time we are going to call a new method and have this timer run every second.


GetWorld()->GetTimerManager().SetTimer(TriggerDestroyTimerHandle, this, &ADestructibleProp::TriggerCountdownToDestroy, 1.f, true);

Then we add in our count down logic


int32 TriggerCountdown;

void TriggerCountdownToDestroy();

Finally we add in our implementation where we modify our count down variable by subtracting one from it every second.

Additionally we trigger a second timer call to our original method by randomly generating a delay before it gets triggered.


void ADestructibleProp::TriggerCountdownToDestroy()
  // count down to zero
  if (--TriggerCountdown <= 0) 
    int32 RandomDelay = FMath::RandRange(1, 5);

    GEngine->AddOnScreenDebugMessage(-1, 3.f, FColor::Orange, "Boom ! with a delay of: " + FString::FromInt(RandomDelay));
    GetWorld()->GetTimerManager().SetTimer(TriggerDestroyTimerHandle, this, &ADestructibleProp::TriggerDestroy, RandomDelay, true);
    GEngine->AddOnScreenDebugMessage(-1, 3.f, FColor::Orange, "Counting down to explosion: " + FString::FromInt(TriggerCountdown));

This allows us to have custom implementations in our timers that perform very specific work.

Pretty cool !


Below you can find a few more links with some additional reading material:

Unreal C++ Props – Part Two- Physics Constraints BONUS: Attack modifiers in C++

By | Development, Props, Tutorial, Unreal | No Comments

Hey guys,

Today we are going to continue evolving our props, this time by introducing physical components.

Physical components allow us to create things like punching bags, springs, various pivot points as well as hanging our player from the ceiling in various sadistic ways. How fun !

In addition to that we are going to throw in some addition attack modifiers so we can easily switch between light, medium and strong attacks.

The starter project is available on our GitHub page.

Below is a bit more reading material for those curious about all the various options in physics constraints:

Unreal C++ Props – Destructible Components

By | Development, Props, Tutorial, Unreal | One Comment

Hey guys,

Today we are going to start introducing props for our character to interact with and I can’t think of anything better then creating a bunch of things to smash.

For this tutorial we will use the Apex Destruction plugin to generate some destructible meshes which we can then hookup to our destructible components.

If you would like to permanently configure this plugin so it’s always enabled here is a quick overview on how plugins are managed in Unreal.

The started project can be found on the GitHub project page.

Additionally here a bunch of links if you would like to read a bit more about these various components:

Unreal Engine C++ Fundamentals – Override UAnimInstance

By | Development, Tutorial, Unreal | No Comments

Hey guys,

This week we continue on with fundamentals, this time going over how to override UAnimInstance in order to have more control and tighter C++ integration with our other classes.

You can find the source code for this video on the GitHub project page.

We looked at UAnimInstance before, have you gone senile !

Last time we looked at UAnimInstance was in the context of using it to access montage controls to give us finer control over our animation playback. This time we are going to move the Event Graph definition from a blue print driven anim instance and migrate all that functionality into our own C++ class.


Why bother rolling our own ? Blueprints are easy !

We can certainly use blueprints for all this work but having low level c++ access gives us a lot of control over our animation settings.

For example if you want to extend your animation system to support Inverse Kinematics, it becomes much simpler to compress that logic via convenient c++ method definitions rather than having to draw out a spaghetti bowl full of blue print nodes that make it hard to debug and troubleshoot.


Let’s take a look at some of the methods involved in this process.

virtual void NativeInitializeAnimation() override;

virtual void NativeUpdateAnimation(float DeltaTimeX) override;

NativeInitializeAnimation allows us to handle initialization of various properties on our animation instance and works similar to the InitializeComponent or BeginPlay methods on the Actor.

NativeUpdateAnimation on the other hand, works similar to the Tick functions and updates the properties for the animation blend spaces to process.


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Now let’s take a look at the actual implementation details.


class UE4FUNDAMENTALS06_API UPlayerAnimInstance : public UAnimInstance
  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Animation")
    bool IsInAir;

  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Animation")
    bool IsAnimationBlended;

  UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Animation")
    float Speed;


  virtual void NativeInitializeAnimation() override;

  virtual void NativeUpdateAnimation(float DeltaTimeX) override;

  APawn* Owner;


void UPlayerAnimInstance::NativeInitializeAnimation()

  // cache the pawn
  Owner = TryGetPawnOwner();

void UPlayerAnimInstance::NativeUpdateAnimation(float DeltaTimeX)

  // double check our pointers make sure nothing is empty
  if (!Owner)

  if (Owner->IsA(AUE4Fundamentals06Character::StaticClass()))
    AUE4Fundamentals06Character* PlayerCharacter = Cast<AUE4Fundamentals06Character>(Owner);
    // again check pointers
    if (PlayerCharacter)
      IsInAir = PlayerCharacter->GetMovementComponent()->IsFalling();
      IsAnimationBlended = PlayerCharacter->GetIsAnimationBlended();
      Speed = PlayerCharacter->GetVelocity().Size();

      GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow, "IsInAir: " + FString(IsInAir ? "true" : "false"));
      GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow, "IsAnimationBlended: " + FString(IsAnimationBlended ? "true" : "false"));
      GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow, "Speed: " + FString::SanitizeFloat(Speed));

As you can see from our code, there is really not much to it.

Outside of overriding the methods you want to take control of the rest comes down how much or how little animation data you want to expose to the blueprint.

The only real major point of complication is to ensure that the pawn attached to this animation instance is correctly cast before you get at it’s details.

With your own anim instance you can now start compartmentalizing your complicated logic, handle various player types against different blend space behaviors and generally modify your animation to suit your game.

For more details check out the links below: