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---
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title: 剖析虚幻渲染体系（09）- 材质体系
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date: 2024-02-04 21:44:37
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excerpt:
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tags:
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rating: ⭐
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---
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# 前言
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https://www.cnblogs.com/timlly/p/15109132.html
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---
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title: 剖析虚幻渲染体系（08）- Shader体系
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date: 2024-02-04 21:44:10
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excerpt:
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tags:
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rating: ⭐
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---
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# 前言
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https://www.cnblogs.com/timlly/p/15092257.html
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@ -48,7 +48,10 @@ rating: ⭐
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- D3D12存储了FD3D12Adapter* Adapter、FD3D12CommandContext* CmdContext、 FD3D12CommandContextRedirector* CmdContextRedirector。
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- FDynamicRHI：FDynamicRHI是由动态绑定的RHI实现的接口，它定义的接口和CommandList、CommandContext比较相似。
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- 代码详见[[#FDynamicRHI]]
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- FRHICommandListExecutor
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- FRHICommandListExecutor：负责将**Renderer层的RHI中间指令转译（或直接调用）到目标平台的图形API**，它在RHI体系中起着举足轻重的作用。
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- FParallelCommandListSet：用于实现并行渲染。使用案例详见[[#FParallelCommandListSet]]。目前5.3只有下面2个子类：
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- FRDGParallelCommandListSet
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- FShadowParallelCommandListSet
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## FDynamicRHI
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```c++
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@ -200,3 +203,535 @@ class RHI_API FDynamicRHI
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>需要注意的是，传统图形API（D3D11、OpenGL）除了继承FDynamicRHI，还需要继承**IRHICommandContextPSOFallback**，因为需要借助后者的接口处理PSO的数据和行为，以保证传统和现代API对PSO的一致处理行为。也正因为此，现代图形API（D3D12、Vulkan、Metal）不需要继承**IRHICommandContext**的任何继承体系的类型，单单直接继承**FDynamicRHI**就可以处理RHI层的所有数据和操作。
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既然现代图形API（D3D12、Vulkan、Metal）的**DynamicRHI**没有继承**IRHICommandContext**的任何继承体系的类型，那么它们是如何实现FDynamicRHI::RHIGetDefaultContext的接口？下面以FD3D12DynamicRHI为例：
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## FParallelCommandListSet
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```c++
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//Engine\Source\Runtime\Renderer\Private\DepthRendering.cpp
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void FDeferredShadingSceneRenderer::RenderPrePass(FRDGBuilder& GraphBuilder, FRDGTextureRef SceneDepthTexture, FInstanceCullingManager& InstanceCullingManager, FRDGTextureRef* FirstStageDepthBuffer)
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{
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RDG_EVENT_SCOPE(GraphBuilder, "PrePass %s %s", GetDepthDrawingModeString(DepthPass.EarlyZPassMode), GetDepthPassReason(DepthPass.bDitheredLODTransitionsUseStencil, ShaderPlatform));
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RDG_CSV_STAT_EXCLUSIVE_SCOPE(GraphBuilder, RenderPrePass);
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RDG_GPU_STAT_SCOPE(GraphBuilder, Prepass);
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SCOPED_NAMED_EVENT(FDeferredShadingSceneRenderer_RenderPrePass, FColor::Emerald);
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SCOPE_CYCLE_COUNTER(STAT_DepthDrawTime);
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const bool bParallelDepthPass = GRHICommandList.UseParallelAlgorithms() && CVarParallelPrePass.GetValueOnRenderThread();
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RenderPrePassHMD(GraphBuilder, SceneDepthTexture);
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if (DepthPass.IsRasterStencilDitherEnabled())
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{
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AddDitheredStencilFillPass(GraphBuilder, Views, SceneDepthTexture, DepthPass);
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}
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auto RenderDepthPass = [&](uint8 DepthMeshPass)
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{
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check(DepthMeshPass == EMeshPass::DepthPass || DepthMeshPass == EMeshPass::SecondStageDepthPass);
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const bool bSecondStageDepthPass = DepthMeshPass == EMeshPass::SecondStageDepthPass;
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if (bParallelDepthPass)
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{
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RDG_WAIT_FOR_TASKS_CONDITIONAL(GraphBuilder, IsDepthPassWaitForTasksEnabled());
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for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ++ViewIndex)
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{
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FViewInfo& View = Views[ViewIndex];
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RDG_GPU_MASK_SCOPE(GraphBuilder, View.GPUMask);
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RDG_EVENT_SCOPE_CONDITIONAL(GraphBuilder, Views.Num() > 1, "View%d", ViewIndex);
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FMeshPassProcessorRenderState DrawRenderState;
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SetupDepthPassState(DrawRenderState);
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const bool bShouldRenderView = View.ShouldRenderView() && (bSecondStageDepthPass ? View.bUsesSecondStageDepthPass : true);
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if (bShouldRenderView)
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{
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View.BeginRenderView();
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FDepthPassParameters* PassParameters = GetDepthPassParameters(GraphBuilder, View, SceneDepthTexture);
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View.ParallelMeshDrawCommandPasses[DepthMeshPass].BuildRenderingCommands(GraphBuilder, Scene->GPUScene, PassParameters->InstanceCullingDrawParams);
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GraphBuilder.AddPass(
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bSecondStageDepthPass ? RDG_EVENT_NAME("SecondStageDepthPassParallel") : RDG_EVENT_NAME("DepthPassParallel"),
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PassParameters,
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ERDGPassFlags::Raster | ERDGPassFlags::SkipRenderPass,
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[this, &View, PassParameters, DepthMeshPass](const FRDGPass* InPass, FRHICommandListImmediate& RHICmdList)
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{
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//并行渲染逻辑主要在这里
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FRDGParallelCommandListSet ParallelCommandListSet(InPass, RHICmdList, GET_STATID(STAT_CLP_Prepass), View, FParallelCommandListBindings(PassParameters));
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ParallelCommandListSet.SetHighPriority();
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View.ParallelMeshDrawCommandPasses[DepthMeshPass].DispatchDraw(&ParallelCommandListSet, RHICmdList, &PassParameters->InstanceCullingDrawParams);
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});
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RenderPrePassEditorPrimitives(GraphBuilder, View, PassParameters, DrawRenderState, DepthPass.EarlyZPassMode, InstanceCullingManager);
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}
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}
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}
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···
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}
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//Engine\Source\Runtime\Renderer\Private\MeshDrawCommands.cpp
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void FParallelMeshDrawCommandPass::DispatchDraw(FParallelCommandListSet* ParallelCommandListSet, FRHICommandList& RHICmdList, const FInstanceCullingDrawParams* InstanceCullingDrawParams) const
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{
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TRACE_CPUPROFILER_EVENT_SCOPE(ParallelMdcDispatchDraw);
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if (MaxNumDraws <= 0)
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{
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return;
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}
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FMeshDrawCommandOverrideArgs OverrideArgs;
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if (InstanceCullingDrawParams)
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{
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OverrideArgs = GetMeshDrawCommandOverrideArgs(*InstanceCullingDrawParams);
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}
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if (ParallelCommandListSet)
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{
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const ENamedThreads::Type RenderThread = ENamedThreads::GetRenderThread();
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FGraphEventArray Prereqs;
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if (ParallelCommandListSet->GetPrereqs())
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{
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Prereqs.Append(*ParallelCommandListSet->GetPrereqs());
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}
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if (TaskEventRef.IsValid())
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{
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Prereqs.Add(TaskEventRef);
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}
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// Distribute work evenly to the available task graph workers based on NumEstimatedDraws.
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// Every task will then adjust it's working range based on FVisibleMeshDrawCommandProcessTask results.
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const int32 NumThreads = FMath::Min<int32>(FTaskGraphInterface::Get().GetNumWorkerThreads(), ParallelCommandListSet->Width);
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const int32 NumTasks = FMath::Min<int32>(NumThreads, FMath::DivideAndRoundUp(MaxNumDraws, ParallelCommandListSet->MinDrawsPerCommandList));
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const int32 NumDrawsPerTask = FMath::DivideAndRoundUp(MaxNumDraws, NumTasks);
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for (int32 TaskIndex = 0; TaskIndex < NumTasks; TaskIndex++)
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{
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const int32 StartIndex = TaskIndex * NumDrawsPerTask;
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const int32 NumDraws = FMath::Min(NumDrawsPerTask, MaxNumDraws - StartIndex);
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checkSlow(NumDraws > 0);
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FRHICommandList* CmdList = ParallelCommandListSet->NewParallelCommandList();
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FGraphEventRef AnyThreadCompletionEvent = TGraphTask<FDrawVisibleMeshCommandsAnyThreadTask>::CreateTask(&Prereqs, RenderThread)
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.ConstructAndDispatchWhenReady(*CmdList, TaskContext.InstanceCullingContext, TaskContext.MeshDrawCommands, TaskContext.MinimalPipelineStatePassSet,
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OverrideArgs,
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TaskContext.InstanceFactor,
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TaskIndex, NumTasks);
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ParallelCommandListSet->AddParallelCommandList(CmdList, AnyThreadCompletionEvent, NumDraws);
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}
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}
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else
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{
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QUICK_SCOPE_CYCLE_COUNTER(STAT_MeshPassDrawImmediate);
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WaitForMeshPassSetupTask(IsInActualRenderingThread() ? EWaitThread::Render : EWaitThread::Task);
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if (TaskContext.bUseGPUScene)
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{
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if (TaskContext.MeshDrawCommands.Num() > 0)
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{
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TaskContext.InstanceCullingContext.SubmitDrawCommands(
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TaskContext.MeshDrawCommands,
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TaskContext.MinimalPipelineStatePassSet,
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OverrideArgs,
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0,
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TaskContext.MeshDrawCommands.Num(),
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TaskContext.InstanceFactor,
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RHICmdList);
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}
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}
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else
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{
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SubmitMeshDrawCommandsRange(TaskContext.MeshDrawCommands, TaskContext.MinimalPipelineStatePassSet, nullptr, 0, 0, TaskContext.bDynamicInstancing, 0, TaskContext.MeshDrawCommands.Num(), TaskContext.InstanceFactor, RHICmdList);
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}
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}
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}
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```
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## 普通Pass渲染
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```c++
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// 代码为UE5旧版本代码
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// Engine\Source\Runtime\RHI\Public\RHIResources.h
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// 渲染通道信息.
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struct FRHIRenderPassInfo
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{
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// 渲染纹理信息.
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struct FColorEntry
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{
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FRHITexture* RenderTarget;
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FRHITexture* ResolveTarget;
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int32 ArraySlice;
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uint8 MipIndex;
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ERenderTargetActions Action;
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};
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FColorEntry ColorRenderTargets[MaxSimultaneousRenderTargets];
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// 深度模板信息.
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struct FDepthStencilEntry
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{
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FRHITexture* DepthStencilTarget;
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FRHITexture* ResolveTarget;
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EDepthStencilTargetActions Action;
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FExclusiveDepthStencil ExclusiveDepthStencil;
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};
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FDepthStencilEntry DepthStencilRenderTarget;
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// 解析参数.
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FResolveParams ResolveParameters;
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// 部分RHI可以使用纹理来控制不同区域的采样和/或阴影分辨率
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FTextureRHIRef FoveationTexture = nullptr;
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// 部分RHI需要一个提示，遮挡查询将在这个渲染通道中使用
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uint32 NumOcclusionQueries = 0;
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bool bOcclusionQueries = false;
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// 部分RHI需要知道，在为部分资源转换生成mip映射的情况下，这个渲染通道是否将读取和写入相同的纹理.
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bool bGeneratingMips = false;
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// 如果这个renderpass应该是多视图，则需要多少视图.
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uint8 MultiViewCount = 0;
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// 部分RHI的提示，渲染通道将有特定的子通道.
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ESubpassHint SubpassHint = ESubpassHint::None;
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// 是否太多UAV.
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bool bTooManyUAVs = false;
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bool bIsMSAA = false;
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// 不同的构造函数.
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// Color, no depth, optional resolve, optional mip, optional array slice
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explicit FRHIRenderPassInfo(FRHITexture* ColorRT, ERenderTargetActions ColorAction, FRHITexture* ResolveRT = nullptr, uint32 InMipIndex = 0, int32 InArraySlice = -1);
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// Color MRTs, no depth
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explicit FRHIRenderPassInfo(int32 NumColorRTs, FRHITexture* ColorRTs[], ERenderTargetActions ColorAction);
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// Color MRTs, no depth
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explicit FRHIRenderPassInfo(int32 NumColorRTs, FRHITexture* ColorRTs[], ERenderTargetActions ColorAction, FRHITexture* ResolveTargets[]);
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// Color MRTs and depth
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explicit FRHIRenderPassInfo(int32 NumColorRTs, FRHITexture* ColorRTs[], ERenderTargetActions ColorAction, FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Color MRTs and depth
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explicit FRHIRenderPassInfo(int32 NumColorRTs, FRHITexture* ColorRTs[], ERenderTargetActions ColorAction, FRHITexture* ResolveRTs[], FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FRHITexture* ResolveDepthRT, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Depth, no color
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explicit FRHIRenderPassInfo(FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FRHITexture* ResolveDepthRT = nullptr, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Depth, no color, occlusion queries
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explicit FRHIRenderPassInfo(FRHITexture* DepthRT, uint32 InNumOcclusionQueries, EDepthStencilTargetActions DepthActions, FRHITexture* ResolveDepthRT = nullptr, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Color and depth
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explicit FRHIRenderPassInfo(FRHITexture* ColorRT, ERenderTargetActions ColorAction, FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Color and depth with resolve
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explicit FRHIRenderPassInfo(FRHITexture* ColorRT, ERenderTargetActions ColorAction, FRHITexture* ResolveColorRT,
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FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FRHITexture* ResolveDepthRT, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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// Color and depth with resolve and optional sample density
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explicit FRHIRenderPassInfo(FRHITexture* ColorRT, ERenderTargetActions ColorAction, FRHITexture* ResolveColorRT,
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FRHITexture* DepthRT, EDepthStencilTargetActions DepthActions, FRHITexture* ResolveDepthRT, FRHITexture* InFoveationTexture, FExclusiveDepthStencil InEDS = FExclusiveDepthStencil::DepthWrite_StencilWrite);
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enum ENoRenderTargets
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{
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NoRenderTargets,
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};
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explicit FRHIRenderPassInfo(ENoRenderTargets Dummy);
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explicit FRHIRenderPassInfo();
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inline int32 GetNumColorRenderTargets() const;
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RHI_API void Validate() const;
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RHI_API void ConvertToRenderTargetsInfo(FRHISetRenderTargetsInfo& OutRTInfo) const;
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(......)
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};
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// Engine\Source\Runtime\RHI\Public\RHICommandList.h
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class RHI_API FRHICommandList : public FRHIComputeCommandList
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{
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public:
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void BeginRenderPass(const FRHIRenderPassInfo& InInfo, const TCHAR* Name)
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{
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if (InInfo.bTooManyUAVs)
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{
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UE_LOG(LogRHI, Warning, TEXT("RenderPass %s has too many UAVs"));
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}
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InInfo.Validate();
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// 直接调用RHI的接口.
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if (Bypass())
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{
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GetContext().RHIBeginRenderPass(InInfo, Name);
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}
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// 分配RHI命令.
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else
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{
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TCHAR* NameCopy = AllocString(Name);
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ALLOC_COMMAND(FRHICommandBeginRenderPass)(InInfo, NameCopy);
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}
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// 设置在RenderPass内标记.
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Data.bInsideRenderPass = true;
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// 缓存活动的RT.
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CacheActiveRenderTargets(InInfo);
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// 重置子Pass.
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ResetSubpass(InInfo.SubpassHint);
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Data.bInsideRenderPass = true;
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}
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void EndRenderPass()
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{
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// 调用或分配RHI接口.
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if (Bypass())
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{
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GetContext().RHIEndRenderPass();
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}
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else
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{
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ALLOC_COMMAND(FRHICommandEndRenderPass)();
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}
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// 重置在RenderPass内标记.
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Data.bInsideRenderPass = false;
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// 重置子Pass标记为None.
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ResetSubpass(ESubpassHint::None);
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}
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};
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```
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它们的使用案例如下：
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主要是`FRHIRenderPassInfo RenderPassInfo(1, ColorRTs, ERenderTargetActions::DontLoad_DontStore)`与`RHICmdList.BeginRenderPass(RenderPassInfo, TEXT("Test_MultiDrawIndirect"))`
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```c++
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bool FRHIDrawTests::Test_MultiDrawIndirect(FRHICommandListImmediate& RHICmdList)
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{
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if (!GRHIGlobals.SupportsMultiDrawIndirect)
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{
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return true;
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}
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// Probably could/should automatically enable in the outer scope when running RHI Unit Tests
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// RenderCaptureInterface::FScopedCapture RenderCapture(true /*bEnable*/, &RHICmdList, TEXT("Test_MultiDrawIndirect"));
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static constexpr uint32 MaxInstances = 8;
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// D3D12 does not have a way to get the base instance ID (SV_InstanceID always starts from 0), so we must emulate it...
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const uint32 InstanceIDs[MaxInstances] = { 0, 1, 2, 3, 4, 5, 6, 7 };
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FBufferRHIRef InstanceIDBuffer = CreateBufferWithData(EBufferUsageFlags::VertexBuffer, ERHIAccess::VertexOrIndexBuffer, TEXT("Test_MultiDrawIndirect_InstanceID"), MakeArrayView(InstanceIDs));
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FVertexDeclarationElementList VertexDeclarationElements;
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VertexDeclarationElements.Add(FVertexElement(0, 0, VET_UInt, 0, 4, true /*per instance frequency*/));
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FVertexDeclarationRHIRef VertexDeclarationRHI = PipelineStateCache::GetOrCreateVertexDeclaration(VertexDeclarationElements);
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const uint16 Indices[3] = { 0, 1, 2 };
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FBufferRHIRef IndexBuffer = CreateBufferWithData(EBufferUsageFlags::IndexBuffer, ERHIAccess::VertexOrIndexBuffer, TEXT("Test_MultiDrawIndirect_IndexBuffer"), MakeArrayView(Indices));
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static constexpr uint32 OutputBufferStride = sizeof(uint32);
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static constexpr uint32 OutputBufferSize = OutputBufferStride * MaxInstances;
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FRHIResourceCreateInfo OutputBufferCreateInfo(TEXT("Test_MultiDrawIndirect_OutputBuffer"));
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FBufferRHIRef OutputBuffer = RHICmdList.CreateBuffer(OutputBufferSize, EBufferUsageFlags::UnorderedAccess | EBufferUsageFlags::SourceCopy, OutputBufferStride, ERHIAccess::UAVCompute, OutputBufferCreateInfo);
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const uint32 CountValues[4] = { 1, 1, 16, 0 };
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FBufferRHIRef CountBuffer = CreateBufferWithData(EBufferUsageFlags::DrawIndirect | EBufferUsageFlags::UnorderedAccess, ERHIAccess::IndirectArgs, TEXT("Test_MultiDrawIndirect_Count"), MakeArrayView(CountValues));
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const FRHIDrawIndexedIndirectParameters DrawArgs[] =
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{
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// IndexCountPerInstance, InstanceCount, StartIndexLocation, BaseVertexLocation, StartInstanceLocation
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{3, 1, 0, 0, 0}, // fill slot 0
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// gap in slot 1
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{3, 2, 0, 0, 2}, // fill slots 2, 3 using 1 sub-draw
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// gap in slot 4
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{3, 1, 0, 0, 5}, // fill slots 5, 6 using 2 sub-draws
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{3, 1, 0, 0, 6},
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{3, 1, 0, 0, 7}, // this draw is expected to never execute
|
||||
};
|
||||
|
||||
const uint32 ExpectedDrawnInstances[MaxInstances] = { 1, 0, 1, 1, 0, 1, 1, 0 };
|
||||
|
||||
FBufferRHIRef DrawArgBuffer = CreateBufferWithData(EBufferUsageFlags::DrawIndirect | EBufferUsageFlags::UnorderedAccess | EBufferUsageFlags::VertexBuffer, ERHIAccess::IndirectArgs,
|
||||
TEXT("Test_MultiDrawIndirect_DrawArgs"), MakeArrayView(DrawArgs));
|
||||
|
||||
FUnorderedAccessViewRHIRef OutputBufferUAV = RHICmdList.CreateUnorderedAccessView(OutputBuffer,
|
||||
FRHIViewDesc::CreateBufferUAV()
|
||||
.SetType(FRHIViewDesc::EBufferType::Typed)
|
||||
.SetFormat(PF_R32_UINT));
|
||||
|
||||
RHICmdList.ClearUAVUint(OutputBufferUAV, FUintVector4(0));
|
||||
|
||||
const FIntPoint RenderTargetSize(4, 4);
|
||||
FRHITextureDesc RenderTargetTextureDesc(ETextureDimension::Texture2D, ETextureCreateFlags::RenderTargetable, PF_B8G8R8A8, FClearValueBinding(), RenderTargetSize, 1, 1, 1, 1, 0);
|
||||
FRHITextureCreateDesc RenderTargetCreateDesc(RenderTargetTextureDesc, ERHIAccess::RTV, TEXT("Test_MultiDrawIndirect_RenderTarget"));
|
||||
FTextureRHIRef RenderTarget = RHICreateTexture(RenderTargetCreateDesc);
|
||||
|
||||
TShaderMapRef<FTestDrawInstancedVS> VertexShader(GetGlobalShaderMap(GMaxRHIFeatureLevel));
|
||||
TShaderMapRef<FTestDrawInstancedPS> PixelShader(GetGlobalShaderMap(GMaxRHIFeatureLevel));
|
||||
|
||||
FGraphicsPipelineStateInitializer GraphicsPSOInit;
|
||||
|
||||
GraphicsPSOInit.BoundShaderState.VertexShaderRHI = VertexShader.GetVertexShader();
|
||||
GraphicsPSOInit.BoundShaderState.VertexDeclarationRHI = VertexDeclarationRHI;
|
||||
GraphicsPSOInit.BoundShaderState.PixelShaderRHI = PixelShader.GetPixelShader();
|
||||
GraphicsPSOInit.DepthStencilState = TStaticDepthStencilState<false, CF_Always>::GetRHI();
|
||||
GraphicsPSOInit.BlendState = TStaticBlendState<>::GetRHI();
|
||||
GraphicsPSOInit.RasterizerState = TStaticRasterizerState<>::GetRHI();
|
||||
GraphicsPSOInit.PrimitiveType = EPrimitiveType::PT_TriangleList;
|
||||
|
||||
FRHITexture* ColorRTs[1] = { RenderTarget.GetReference() };
|
||||
FRHIRenderPassInfo RenderPassInfo(1, ColorRTs, ERenderTargetActions::DontLoad_DontStore);
|
||||
|
||||
RHICmdList.Transition(FRHITransitionInfo(OutputBufferUAV, ERHIAccess::UAVCompute, ERHIAccess::UAVGraphics, EResourceTransitionFlags::None));
|
||||
RHICmdList.BeginUAVOverlap(); // Output UAV can be written without syncs between draws (each draw is expected to write into different slots)
|
||||
|
||||
RHICmdList.BeginRenderPass(RenderPassInfo, TEXT("Test_MultiDrawIndirect"));
|
||||
RHICmdList.SetViewport(0, 0, 0, float(RenderTargetSize.X), float(RenderTargetSize.Y), 1);
|
||||
|
||||
RHICmdList.ApplyCachedRenderTargets(GraphicsPSOInit);
|
||||
SetGraphicsPipelineState(RHICmdList, GraphicsPSOInit, 0);
|
||||
|
||||
check(InstanceIDBuffer->GetStride() == 4);
|
||||
RHICmdList.SetStreamSource(0, InstanceIDBuffer, 0);
|
||||
|
||||
FRHIBatchedShaderParameters ShaderParameters;
|
||||
ShaderParameters.SetUAVParameter(PixelShader->OutDrawnInstances.GetBaseIndex(), OutputBufferUAV);
|
||||
RHICmdList.SetBatchedShaderParameters(PixelShader.GetPixelShader(), ShaderParameters);
|
||||
|
||||
const uint32 DrawArgsStride = sizeof(DrawArgs[0]);
|
||||
const uint32 CountStride = sizeof(CountValues[0]);
|
||||
|
||||
RHICmdList.MultiDrawIndexedPrimitiveIndirect(IndexBuffer,
|
||||
DrawArgBuffer, DrawArgsStride*0, // 1 sub-draw with instance index 0
|
||||
CountBuffer, CountStride*0, // count buffer contains 1 in this slot
|
||||
5 // expect to draw only 1 instance due to GPU-side upper bound
|
||||
);
|
||||
|
||||
RHICmdList.MultiDrawIndexedPrimitiveIndirect(IndexBuffer,
|
||||
DrawArgBuffer, DrawArgsStride*1, // 1 sub-draw with 2 instances at base index 2
|
||||
CountBuffer, CountStride*1, // count buffer contains 1 in this slot
|
||||
4 // expect to draw only 1 instance due to GPU-side upper bound
|
||||
);
|
||||
|
||||
RHICmdList.MultiDrawIndexedPrimitiveIndirect(IndexBuffer,
|
||||
DrawArgBuffer, DrawArgsStride*2, // 2 sub-draws with 1 instance each starting at base index 5
|
||||
CountBuffer, CountStride*2, // count buffer contains 16 in this slot
|
||||
2 // expect to draw only 2 instances due to CPU-side upper bound
|
||||
);
|
||||
|
||||
RHICmdList.MultiDrawIndexedPrimitiveIndirect(IndexBuffer,
|
||||
DrawArgBuffer, DrawArgsStride*4, // 1 sub-draw with 1 instance each starting at base index 7
|
||||
CountBuffer, CountStride*3, // count buffer contains 0 in this slot
|
||||
1 // expect to skip the draw due to GPU-side count of 0
|
||||
);
|
||||
|
||||
RHICmdList.MultiDrawIndexedPrimitiveIndirect(IndexBuffer,
|
||||
DrawArgBuffer, DrawArgsStride*4, // 1 sub-draw with 1 instance each starting at base index 7
|
||||
CountBuffer, CountStride*0, // count buffer contains 1 in this slot
|
||||
0 // expect to skip the draw due to CPU-side count of 0
|
||||
);
|
||||
|
||||
RHICmdList.EndRenderPass();
|
||||
|
||||
RHICmdList.EndUAVOverlap();
|
||||
|
||||
RHICmdList.Transition(FRHITransitionInfo(OutputBufferUAV, ERHIAccess::UAVGraphics, ERHIAccess::CopySrc, EResourceTransitionFlags::None));
|
||||
|
||||
TConstArrayView<uint8> ExpectedOutputView = MakeArrayView(reinterpret_cast<const uint8*>(ExpectedDrawnInstances), sizeof(ExpectedDrawnInstances));
|
||||
bool bSucceeded = FRHIBufferTests::VerifyBufferContents(TEXT("Test_MultiDrawIndirect"), RHICmdList, OutputBuffer, ExpectedOutputView);
|
||||
|
||||
return bSucceeded;
|
||||
}
|
||||
```
|
||||
|
||||
## Subpass
|
||||
先说一下Subpass的由来、作用和特点。
|
||||
|
||||
在传统的多Pass渲染中，每个Pass结束时通常会渲染出一组渲染纹理，部分成为着色器参数提供给下一个Pass采样读取。这种纹理采样方式不受任何限制，可以读取任意的领域像素，使用任意的纹理过滤方式。这种方式虽然使用灵活，但在TBR（Tile-Based Renderer）硬件架构的设备中会有较大的消耗：渲染纹理的Pass通常会将渲染结果存储在On-chip的Tile Memory中，待Pass结束后会写回GPU显存（VRAM）中，写回GPU显存是个耗时耗耗电的操作。
|
||||
|
||||
|
||||
|
||||
_传统多Pass之间的内存存取模型，多次发生于On-Chip和全局存储器之间。_
|
||||
|
||||
如果出现一种特殊的纹理使用情况：上一个Pass渲染处理的纹理，立即被下一个Pass使用，并且下一个Pass只采样像素位置自身的数据，而不需要采样邻域像素的位置。这种情况就符合了Subpass的使用情景。使用Subpass渲染的纹理结果只会存储在Tile Memory中，在Subpass结束后不会写回VRAM，而直接提供Tile Memory的数据给下一个Subpass采样读取。这样就避免了传统Pass结束写回GPU显存以及下一个Pass又从GPU显存读数据的耗时耗电操作，从而提升了性能。
|
||||
|
||||
|
||||
|
||||
_Subpass之间的内存存取模型，都发生在On-Chip内。_
|
||||
|
||||
Subpass的相关代码主要集中在移动端中。UE涉及Subpass的接口和类型如下：
|
||||
```c++
|
||||
// 提供给RHI的Subpass标记.
|
||||
enum class ESubpassHint : uint8
|
||||
{
|
||||
None, // 传统渲染(非Subpass)
|
||||
DepthReadSubpass, // 深度读取Subpass.
|
||||
DeferredShadingSubpass, // 移动端延迟着色Subpass.
|
||||
};
|
||||
|
||||
|
||||
// Engine\Source\Runtime\RHI\Public\RHICommandList.h
|
||||
|
||||
class RHI_API FRHICommandListBase : public FNoncopyable
|
||||
{
|
||||
(......)
|
||||
|
||||
protected:
|
||||
// PSO上下文.
|
||||
struct FPSOContext
|
||||
{
|
||||
uint32 CachedNumSimultanousRenderTargets = 0;
|
||||
TStaticArray<FRHIRenderTargetView, MaxSimultaneousRenderTargets> CachedRenderTargets;
|
||||
FRHIDepthRenderTargetView CachedDepthStencilTarget;
|
||||
|
||||
// Subpass提示标记.
|
||||
ESubpassHint SubpassHint = ESubpassHint::None;
|
||||
uint8 SubpassIndex = 0;
|
||||
uint8 MultiViewCount = 0;
|
||||
bool HasFragmentDensityAttachment = false;
|
||||
} PSOContext;
|
||||
};
|
||||
|
||||
class RHI_API FRHICommandList : public FRHIComputeCommandList
|
||||
{
|
||||
public:
|
||||
void BeginRenderPass(const FRHIRenderPassInfo& InInfo, const TCHAR* Name)
|
||||
{
|
||||
(......)
|
||||
|
||||
CacheActiveRenderTargets(InInfo);
|
||||
// 设置Subpass数据.
|
||||
ResetSubpass(InInfo.SubpassHint);
|
||||
Data.bInsideRenderPass = true;
|
||||
}
|
||||
|
||||
void EndRenderPass()
|
||||
{
|
||||
(......)
|
||||
|
||||
// 重置Subpass标记为None.
|
||||
ResetSubpass(ESubpassHint::None);
|
||||
}
|
||||
|
||||
// 下一个Subpass.
|
||||
void NextSubpass()
|
||||
{
|
||||
// 分配或调用RHI接口.
|
||||
if (Bypass())
|
||||
{
|
||||
GetContext().RHINextSubpass();
|
||||
}
|
||||
else
|
||||
{
|
||||
ALLOC_COMMAND(FRHICommandNextSubpass)();
|
||||
}
|
||||
|
||||
// 增加Subpass计数.
|
||||
IncrementSubpass();
|
||||
}
|
||||
|
||||
// 增加subpass计数.
|
||||
void IncrementSubpass()
|
||||
{
|
||||
PSOContext.SubpassIndex++;
|
||||
}
|
||||
|
||||
// 重置Subpass数据.
|
||||
void ResetSubpass(ESubpassHint SubpassHint)
|
||||
{
|
||||
PSOContext.SubpassHint = SubpassHint;
|
||||
PSOContext.SubpassIndex = 0;
|
||||
}
|
||||
};
|
||||
```
|
||||
@ -0,0 +1,9 @@
|
||||
---
|
||||
title: 剖析虚幻渲染体系（11）- RDG
|
||||
date: 2024-02-04 21:42:54
|
||||
excerpt:
|
||||
tags:
|
||||
rating: ⭐
|
||||
---
|
||||
# 前言
|
||||
https://www.cnblogs.com/timlly/p/15217090.html
|
||||
8
03-UnrealEngine/性能优化/c++内存泄漏分析工具.md
Normal file
8
03-UnrealEngine/性能优化/c++内存泄漏分析工具.md
Normal file
@ -0,0 +1,8 @@
|
||||
---
|
||||
title: c++内存泄漏分析工具
|
||||
date: 2024-02-04 21:15:26
|
||||
excerpt:
|
||||
tags:
|
||||
rating: ⭐
|
||||
---
|
||||
https://github.com/dpull/tracing_malloc?tab=readme-ov-file
|
||||
Loading…
x
Reference in New Issue
Block a user