Get the transform of actors in each substep of physics simulation?

Development Programming & Scripting
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1

Is it possible to get the pose of an actor for every substep of the physics simulation in Unreal Engine 5?

In Unreal Engine 4, you can add a callback function to the OnPhysScene[...] delegates, e.g.:

primitiveComponent->GetBodyInstance()->GetPhysicsScene()->OnPhysScenePostTick.AddUFunction(this, "SubstepFunction");

or use the FCalculateCustomPhysics delegate, which was introduced by the following pull request: https://github.com/EpicGames/UnrealEngine/pull/585. Howevery, since Unreal Engine 5, these delegates are only called for every tick, not every substep anymore.

2

If anyone has the same problem: I solved it using the AsyncPhysicsTickActor function.

I activated the tick by setting bAsyncPhysicsTickEnabled = true; in the constructor, then I overrode the function:

virtual void AsyncPhysicsTickActor(float DeltaTime, float SimTime) override;

and implemented it this way:

void AROS2Robot::AsyncPhysicsTickActor(float DeltaTime, float SimTime){
    UPrimitiveComponent* primComponent = static_cast<UPrimitiveComponent*>(GetRootComponent());

    if (primComponent != nullptr && primComponent->GetBodyInstance() != nullptr && primComponent->GetBodyInstance()->ActorHandle != nullptr) {
        Chaos::FRigidBodyHandle_Internal* Handle = primComponent->GetBodyInstance()->ActorHandle->GetPhysicsThreadAPI();
            
        // The transform of the actor with substepping precision:
        FTransform worldPos = Chaos::FParticleUtilitiesGT::GetCoMWorldTransform(Handle);
    }
}
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