Method HandleStep

Source/URLab/Private/Bridge/RpcDispatcher.cpp:969–1333

// =============================================================================

TSharedPtr<FJsonObject> FURLabRpcDispatcher::HandleStep(const TSharedPtr<FJsonObject>& Req)
{
	AAMjManager* Mgr = OwnerMgr.Get();
	if (!Mgr || !Mgr->PhysicsEngine || !Mgr->PhysicsEngine->m_model)
	{
		return MakeError(TEXT("not_ready"), TEXT("PhysicsEngine not initialised"));
	}

	if (ActiveStepMode == EStepMode::Live)
	{
		// Live mode: UE drives its own physics. step() applies ctrl and
		// returns current state. n_steps is ignored (UE steps at its own
		// rate). Same per_articulation shape as direct mode.
		mjModel* m = Mgr->PhysicsEngine->GetModel();
		mjData* d = Mgr->PhysicsEngine->GetData();

		FMjStepRequest TmpReq;
		const TSharedPtr<FJsonObject>* PerArt = nullptr;
		if (Req->TryGetObjectField(TEXT("per_articulation"), PerArt) && PerArt && PerArt->IsValid())
		{
			for (auto& Pair : (*PerArt)->Values)
			{
				const TSharedPtr<FJsonObject>* ArtObj = nullptr;
				if (!Pair.Value->TryGetObject(ArtObj) || !ArtObj || !ArtObj->IsValid())
					continue;

				FString CtlMode;
				if ((*ArtObj)->TryGetStringField(TEXT("control_mode"), CtlMode))
					TmpReq.PerArticulationControlMode.Add(Pair.Key, CtlMode);

				const TArray<TSharedPtr<FJsonValue>>* CtrlList = nullptr;
				if ((*ArtObj)->TryGetArrayField(TEXT("ctrl"), CtrlList) && CtrlList)
				{
					if (AMjArticulation* Art = Cast<AMjArticulation>(Mgr->GetArticulation(Pair.Key)))
					{
						TArray<UMjActuator*> Acts = Art->GetActuators();
						for (int32 i = 0; i < CtrlList->Num() && i < Acts.Num(); ++i)
						{
							UMjActuator* A = Acts[i];
							if (!A)
								continue;
							FString Local = A->GetMjName();
							FString Prefix = Art->GetName() + TEXT("_");
							if (Local.StartsWith(Prefix))
								Local = Local.Mid(Prefix.Len());
							TmpReq.PerArticulationCtrl.FindOrAdd(Pair.Key).Add(
								{Local, (float)(*CtrlList)[i]->AsNumber()});
						}
					}
				}
			}
		}

		TSharedPtr<FJsonObject> Reply = MakeShared<FJsonObject>();
		{
			FScopeLock Lock(&Mgr->PhysicsEngine->CallbackMutex);
			ApplyStepCtrl(Mgr, TmpReq, m, d);
			Reply->SetStringField(TEXT("op"), TEXT("step_ok"));