How do I call a Blueprint Timeline from C++?

Blueprint Timelines aren’t directly addressable in C++. For C++ equivalents, create a UTimelineComponent in code. Or call the Blueprint function from C++ via UFunction reflection — awkward but works.

How do I set up a TimelineComponent in C++?

Create UTimelineComponent, add float tracks via AddInterpFloat with a UCurveFloat asset, set callbacks via SetTimelinePostUpdateFunc and SetTimelineFinishedFunc, then Play. Register the component in your actor’s constructor or BeginPlay.

What if my Timeline plays in editor but not at runtime?

BeginPlay must complete before Play is safe. Calling Play from constructor produces undefined behavior. Move to BeginPlay or a later lifecycle method.

Fix: Unreal Blueprint Timeline Not Playing From Script

Quick answer: Create a UTimelineComponent in C++ and call Play in BeginPlay. Blueprint-only Timelines aren’t directly callable from C++ — use the component-based equivalent.

A door BP has a Timeline opening it. You want to trigger this from a C++ controller. Direct access to the Timeline isn’t exposed. The Blueprint-only Timeline is internal to the Blueprint VM.

UTimelineComponent in C++

// In header
UPROPERTY()
UTimelineComponent* OpenTimeline;

UPROPERTY(EditAnywhere)
UCurveFloat* OpenCurve;

// Constructor
ADoor::ADoor() {
    OpenTimeline = CreateDefaultSubobject<UTimelineComponent>(TEXT("OpenTimeline"));
}

// BeginPlay
void ADoor::BeginPlay() {
    Super::BeginPlay();
    FOnTimelineFloat updateFn;
    updateFn.BindDynamic(this, &ADoor::OnTimelineUpdate);
    OpenTimeline->AddInterpFloat(OpenCurve, updateFn);
    OpenTimeline->SetLooping(false);
}

// Trigger
void ADoor::Open() {
    OpenTimeline->Play();
}

// Callback per tick
UFUNCTION()
void ADoor::OnTimelineUpdate(float Value) {
    SetActorLocation(StartLoc + FVector(0, 0, Value * 100));
}

Component-based, callable from anywhere. Plays a UCurveFloat over its assigned duration.

Calling Blueprint Functions from C++

If the Timeline lives in a Blueprint and you can’t port:

UFunction* func = doorActor->FindFunction(TEXT("OpenDoor"));
if (func) {
    doorActor->ProcessEvent(func, nullptr);
}

Calls the Blueprint OpenDoor function (which can in turn play its Timeline). Awkward but works without porting.

BlueprintCallable Wrapper

A cleaner alternative: mark the BP function BlueprintCallable and use the generated reflection:

IDoorActor::Execute_OpenDoor(doorActor);   // if interface-based

Or assign the door BP to a UPROPERTY of an interface type and call its method — routes through Blueprint normally.

Verifying

Trigger Open from C++. Door should animate. Print UE_LOG at Play call to confirm it’s reached. If the actor is selected, the Timeline track visualization should advance in the editor.

“Blueprint Timelines and C++ Timelines are different APIs. Convert to UTimelineComponent for cross-language access, or call BP functions via reflection.”

For doors and other simple lerps, a manual FMath::Lerp in Tick is often simpler than a Timeline component.