_AssumesLocked variations of BodyInstance methods

Development World Creation
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1

Hello,

does anyone know what _AssumesLocked variations of methods like “GetUnrealWorldVelocity” do?

I’ve look through github and found only that they are using methods also named _AssumesLocked.

When should I use them instead? There is NOTHING anywhere about them.

Thanks

2

Any chance you’ve found out? Since this is like the only mention of it :frowning:

FVector FBodyInstance::GetUnrealWorldAngularVelocityInRadians() const
{
	FVector OutVelocity = FVector::ZeroVector;

	FPhysicsCommand::ExecuteRead(ActorHandle, [&](const FPhysicsActorHandle& Actor)
	{
		OutVelocity = FPhysicsInterface::GetAngularVelocity_AssumesLocked(Actor);
	});

	return OutVelocity;
}

I can see that it just doesn’t “execute read”

FVector FBodyInstance::GetUnrealWorldAngularVelocityInRadians_AssumesLocked() const
{
	return FPhysicsInterface::GetAngularVelocity_AssumesLocked(ActorHandle);
}

That execute read works with some sort of lock, i guess:

bool FPhysicsCommand_PhysX::ExecuteRead(const FPhysicsActorHandle_PhysX& InActorHandle, TFunctionRef<void(const FPhysicsActorHandle_PhysX& Actor)> InCallable)
{
	if(InActorHandle.IsValid())
	{
		FPhysicsInterfaceScopedLock_PhysX ScopeLock(&InActorHandle, EPhysicsInterfaceScopedLockType::Read);
		InCallable(InActorHandle);

		return true;
	}

	return false;
}

So I assume that PhysX is able to be multithreaded with read/write locks and from that I assume that unreal uses it in a single threaded fashion, so we can shave some time on all the unnecessary locking/unlocking. But I would love it if someone were to confirm that.

3

I mean it is not a bad assumption, but sadly no, I’ve never found out what they do and decided not to use them until I come across some bottleneck. I was afraid it would cause more trouble down the road since I wasn’t and still am not sure what kind of lock we are reffering to. However, since AFAIK UE4 physics runs on its own single thread and if you are correct, then yes, it could help with performance, however I believe aquiring lock is really fast if no one else holds it so eh.