Method OnReplayStep

Source/URLab/Private/Replay/MjReplayManager.cpp:972–1277

}

void AMjReplayManager::OnReplayStep(mjModel* m, mjData* d)
{
	if (!bIsReplaying || !m || !d)
		return;

	TArray<FMjReplayFrame>& Frames = GetActiveFrames();
	if (Frames.Num() == 0)
		return;

	// Advance playback time on the physics thread (no race condition)
	double PhysDt = m->opt.timestep;
	double CurrentPT = PhysicsPlaybackTime.load(std::memory_order_relaxed);
	if (Manager->PhysicsEngine && !Manager->PhysicsEngine->bIsPaused)
	{
		CurrentPT += PhysDt;
		double TotalDuration = Frames.Last().Timestamp - Frames[0].Timestamp;
		if (TotalDuration > 0 && CurrentPT > TotalDuration)
		{
			CurrentPT = 0.0; // Loop
		}
		PhysicsPlaybackTime.store(CurrentPT, std::memory_order_relaxed);
	}

	double StartTime = Frames[0].Timestamp;
	double TargetTime = StartTime + CurrentPT;

	int32 FoundIdx = Algo::LowerBound(Frames, TargetTime,
		[](const FMjReplayFrame& Frame, double T) { return Frame.Timestamp < T; });
	if (FoundIdx > 0)
		--FoundIdx;
	FoundIdx = FMath::Clamp(FoundIdx, 0, Frames.Num() - 1);

	// Compute interpolation alpha between FoundIdx and FoundIdx+1
	int32 NextIdx = FMath::Min(FoundIdx + 1, Frames.Num() - 1);
	double Alpha = 0.0;
	if (bInterpolateFrames && NextIdx > FoundIdx)
	{
		double T0 = Frames[FoundIdx].Timestamp;
		double T1 = Frames[NextIdx].Timestamp;
		double Span = T1 - T0;
		if (Span > 1e-9)
		{
			Alpha = FMath::Clamp((TargetTime - T0) / Span, 0.0, 1.0);
		}
	}

	const FMjReplayFrame& Frame = Frames[FoundIdx];

	bool bFirstFrame = bFirstReplayFrame;
	if (d->time - LastReplayLogTime > 1.0)
	{
		UE_LOG(LogURLabReplay, Log, TEXT("ReplayManager: Playing '%s' Frame %f (PlaybackTime: %f). Index %d/%d"),
			*ActiveSessionName, Frame.Timestamp, PlaybackTime, FoundIdx, Frames.Num());
		LastReplayLogTime = d->time;
	}

	int32 MatchedJoints = 0;
	int32 UnmatchedJoints = 0;