UE4 tick

在GuardedMain中，如果没有退出命令的话，我们会移植在EngineTick中。

FMemMark MemStackMark(FMemStack::Get());

FThreadHeartBeat::Get().HeartBeat(true);

FGameThreadHitchHeartBeat::Get().FrameStart();

FPlatformMisc::TickHotfixables();

//如果没有多线程的话，我们通过游戏线程进行渲染线程心跳检测

TickRenderingTickables();

//发生在第一帧，主线程等待渲染线程完成所有的renderingcommands

FlushRenderingCommands();

GEngine-\>UpdateTimeAndHandleMaxTickRate();

//通知渲染线程的scene及逆行所有的primitivescene的更新

for (const FWorldContext& Context : GEngine-\>GetWorldContexts())

{

UWorld\* CurrentWorld = Context.World();

if (CurrentWorld)

{

FSceneInterface\* Scene = CurrentWorld-\>Scene;

ENQUEUE_RENDER_COMMAND(UpdateScenePrimitives)(

[Scene](FRHICommandListImmediate& RHICmdList)

{

Scene-\>UpdateAllPrimitiveSceneInfos(RHICmdList);

});

}

}

// BeginFrameRenderThread(RHICmdList, CurrentFrameCounter);

//Scene-\>StartFrame();

//当不是editor的时候

GEngine-\>EmitDynamicResolutionEvent(EDynamicResolutionStateEvent::BeginFrame);

GMalloc-\>UpdateStats();

//计算FPS

CalculateFPSTimings();

FlushPendingDeleteRHIResources_RenderThread();

FPlatformApplicationMisc::PumpMessages(true);

bIdleMode = ShouldUseIdleMode();

FPlatformProcess::Sleep(.1f);

SlateApp.PollGameDeviceState();

SlateApp.FinishedInputThisFrame();

//tick media framework

MediaModule-\>TickPreEngine();

//主的game tick

GEngine-\>Tick(FApp::GetDeltaTime(), bIdleMode);

//异步的shader编译

GShaderCompilingManager-\>ProcessAsyncResults(true, false);

//

GDistanceFieldAsyncQueue-\>ProcessAsyncTasks();

//

MediaModule-\>TickPreSlate();

//

ProcessLocalPlayerSlateOperations();

//处理slate的逻辑

//……

FSlateApplication::Get().Tick();

FModuleManager::GetModuleChecked\<IAutomationControllerModule\>(AutomationController).Tick();

FModuleManager::GetModuleChecked\<IAutomationWorkerModule\>(AutomationWorkerModuleName).Tick();

//tick RHI

RHITick( FApp::GetDeltaTime() ); // Update RHI.

GFrameCounter++;

//得到所有需要cleaned up 的object

PendingCleanupObjects = GetPendingCleanupObjects();

//同步主线程和渲染线程

{

SCOPE_CYCLE_COUNTER(STAT_FrameSyncTime);

// this could be perhaps moved down to get greater parallelism

// Sync game and render thread. Either total sync or allowing one frame lag.

static FFrameEndSync FrameEndSync;

static auto CVarAllowOneFrameThreadLag =
IConsoleManager::Get().FindTConsoleVariableDataInt(TEXT("r.OneFrameThreadLag"));

FrameEndSync.Sync( CVarAllowOneFrameThreadLag-\>GetValueOnGameThread() != 0 );

}

//删除之前的object

delete PreviousPendingCleanupObjects;

//deferred commands

GEngine-\>TickDeferredCommands();

//MediaModule-\>TickPostRender();

// end of RHI frame

EndFrameRenderThread(RHICmdList);