378 lines
17 KiB
Markdown
378 lines
17 KiB
Markdown
---
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title: Untitled
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date: 2024-09-26 18:41:24
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excerpt:
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tags:
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rating: ⭐
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---
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# RenderBasePass()
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传入RenderBasePass()的DepthStencil逻辑如下：
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```c++
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const FExclusiveDepthStencil::Type BasePassDepthStencilAccess =
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bAllowReadOnlyDepthBasePass
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? FExclusiveDepthStencil::DepthRead_StencilWrite
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: FExclusiveDepthStencil::DepthWrite_StencilWrite;
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```
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FDeferredShadingSceneRenderer::RenderBasePass() =>
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FDeferredShadingSceneRenderer::RenderBasePassInternal() =>
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FBasePassMeshProcessor::TryAddMeshBatch =>
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## 大致流程
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1. 创建MRT并绑定、取得深度缓存。
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```c++
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const FExclusiveDepthStencil ExclusiveDepthStencil(BasePassDepthStencilAccess);
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TStaticArray<FTextureRenderTargetBinding, MaxSimultaneousRenderTargets> BasePassTextures;
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uint32 BasePassTextureCount = SceneTextures.GetGBufferRenderTargets(BasePassTextures);
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Strata::AppendStrataMRTs(*this, BasePassTextureCount, BasePassTextures);
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TArrayView<FTextureRenderTargetBinding> BasePassTexturesView = MakeArrayView(BasePassTextures.GetData(), BasePassTextureCount);
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FRDGTextureRef BasePassDepthTexture = SceneTextures.Depth.Target;
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```
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2. GBuffer Clear
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```c++
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GraphBuilder.AddPass(RDG_EVENT_NAME("GBufferClear"), PassParameters, ERDGPassFlags::Raster,
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[PassParameters, ColorLoadAction, SceneColorClearValue](FRHICommandList& RHICmdList)
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{
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// If no fast-clear action was used, we need to do an MRT shader clear.
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if (ColorLoadAction == ERenderTargetLoadAction::ENoAction)
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{
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const FRenderTargetBindingSlots& RenderTargets = PassParameters->RenderTargets;
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FLinearColor ClearColors[MaxSimultaneousRenderTargets];
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FRHITexture* Textures[MaxSimultaneousRenderTargets];
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int32 TextureIndex = 0;
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RenderTargets.Enumerate([&](const FRenderTargetBinding& RenderTarget)
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{
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FRHITexture* TextureRHI = RenderTarget.GetTexture()->GetRHI();
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ClearColors[TextureIndex] = TextureIndex == 0 ? SceneColorClearValue : TextureRHI->GetClearColor();
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Textures[TextureIndex] = TextureRHI;
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++TextureIndex;
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});
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// Clear color only; depth-stencil is fast cleared.
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DrawClearQuadMRT(RHICmdList, true, TextureIndex, ClearColors, false, 0, false, 0);
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}
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});
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```
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3. RenderTargetBindingSlots
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```c++
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// Render targets bindings should remain constant at this point.
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FRenderTargetBindingSlots BasePassRenderTargets = GetRenderTargetBindings(ERenderTargetLoadAction::ELoad, BasePassTexturesView);
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BasePassRenderTargets.DepthStencil = FDepthStencilBinding(BasePassDepthTexture, ERenderTargetLoadAction::ELoad, ERenderTargetLoadAction::ELoad, ExclusiveDepthStencil);
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```
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4. RenderBasePassInternal()
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5. RenderAnisotropyPass()
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# MeshDraw
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## RenderBasePassInternal()
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RenderNaniteBasePass()为一个Lambda，最终调用**Nanite::DrawBasePass()** 渲染Nanite物体的BasePass。其他相关渲染代码如下：
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```c++
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SCOPE_CYCLE_COUNTER(STAT_BasePassDrawTime);
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RDG_EVENT_SCOPE(GraphBuilder, "BasePass");
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RDG_GPU_STAT_SCOPE(GraphBuilder, Basepass);
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const bool bDrawSceneViewsInOneNanitePass = Views.Num() > 1 && Nanite::ShouldDrawSceneViewsInOneNanitePass(Views[0]);
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if (bParallelBasePass)//并行渲染模式
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{
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RDG_WAIT_FOR_TASKS_CONDITIONAL(GraphBuilder, IsBasePassWaitForTasksEnabled());
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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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View.BeginRenderView();
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const bool bLumenGIEnabled = GetViewPipelineState(View).DiffuseIndirectMethod == EDiffuseIndirectMethod::Lumen;
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FMeshPassProcessorRenderState DrawRenderState;
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SetupBasePassState(BasePassDepthStencilAccess, ViewFamily.EngineShowFlags.ShaderComplexity, DrawRenderState);
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FOpaqueBasePassParameters* PassParameters = GraphBuilder.AllocParameters<FOpaqueBasePassParameters>();
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PassParameters->View = View.GetShaderParameters();
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PassParameters->ReflectionCapture = View.ReflectionCaptureUniformBuffer;
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PassParameters->BasePass = CreateOpaqueBasePassUniformBuffer(GraphBuilder, View, ViewIndex, ForwardBasePassTextures, DBufferTextures, bLumenGIEnabled);
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PassParameters->RenderTargets = BasePassRenderTargets;
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PassParameters->RenderTargets.ShadingRateTexture = GVRSImageManager.GetVariableRateShadingImage(GraphBuilder, View, FVariableRateShadingImageManager::EVRSPassType::BasePass);
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const bool bShouldRenderView = View.ShouldRenderView();
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if (bShouldRenderView)
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{
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View.ParallelMeshDrawCommandPasses[EMeshPass::BasePass].BuildRenderingCommands(GraphBuilder, Scene->GPUScene, PassParameters->InstanceCullingDrawParams);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("BasePassParallel"),
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PassParameters,
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ERDGPassFlags::Raster | ERDGPassFlags::SkipRenderPass,
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[this, &View, PassParameters](const FRDGPass* InPass, FRHICommandListImmediate& RHICmdList)
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{
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FRDGParallelCommandListSet ParallelCommandListSet(InPass, RHICmdList, GET_STATID(STAT_CLP_BasePass), View, FParallelCommandListBindings(PassParameters));
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View.ParallelMeshDrawCommandPasses[EMeshPass::BasePass].DispatchDraw(&ParallelCommandListSet, RHICmdList, &PassParameters->InstanceCullingDrawParams);
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});
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}
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const bool bShouldRenderViewForNanite = bNaniteEnabled && (!bDrawSceneViewsInOneNanitePass || ViewIndex == 0); // when bDrawSceneViewsInOneNanitePass, the first view should cover all the other atlased ones
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if (bShouldRenderViewForNanite)
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{
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// Should always have a full Z prepass with Nanite
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check(ShouldRenderPrePass());
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//渲染Nanite物体BasePass
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RenderNaniteBasePass(View, ViewIndex);
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}
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//渲染编辑器相关的图元物体
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RenderEditorPrimitives(GraphBuilder, PassParameters, View, DrawRenderState, InstanceCullingManager);
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//渲染大气
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if (bShouldRenderView && View.Family->EngineShowFlags.Atmosphere)
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{
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FOpaqueBasePassParameters* SkyPassPassParameters = GraphBuilder.AllocParameters<FOpaqueBasePassParameters>();
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SkyPassPassParameters->BasePass = PassParameters->BasePass;
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SkyPassPassParameters->RenderTargets = BasePassRenderTargets;
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SkyPassPassParameters->View = View.GetShaderParameters();
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SkyPassPassParameters->ReflectionCapture = View.ReflectionCaptureUniformBuffer;
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View.ParallelMeshDrawCommandPasses[EMeshPass::SkyPass].BuildRenderingCommands(GraphBuilder, Scene->GPUScene, SkyPassPassParameters->InstanceCullingDrawParams);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("SkyPassParallel"),
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SkyPassPassParameters,
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ERDGPassFlags::Raster | ERDGPassFlags::SkipRenderPass,
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[this, &View, SkyPassPassParameters](const FRDGPass* InPass, FRHICommandListImmediate& RHICmdList)
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{
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FRDGParallelCommandListSet ParallelCommandListSet(InPass, RHICmdList, GET_STATID(STAT_CLP_BasePass), View, FParallelCommandListBindings(SkyPassPassParameters));
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View.ParallelMeshDrawCommandPasses[EMeshPass::SkyPass].DispatchDraw(&ParallelCommandListSet, RHICmdList, &SkyPassPassParameters->InstanceCullingDrawParams);
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});
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}
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}
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}
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else
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{
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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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View.BeginRenderView();
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const bool bLumenGIEnabled = GetViewPipelineState(View).DiffuseIndirectMethod == EDiffuseIndirectMethod::Lumen;
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FMeshPassProcessorRenderState DrawRenderState;
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SetupBasePassState(BasePassDepthStencilAccess, ViewFamily.EngineShowFlags.ShaderComplexity, DrawRenderState);
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FOpaqueBasePassParameters* PassParameters = GraphBuilder.AllocParameters<FOpaqueBasePassParameters>();
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PassParameters->View = View.GetShaderParameters();
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PassParameters->ReflectionCapture = View.ReflectionCaptureUniformBuffer;
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PassParameters->BasePass = CreateOpaqueBasePassUniformBuffer(GraphBuilder, View, ViewIndex, ForwardBasePassTextures, DBufferTextures, bLumenGIEnabled);
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PassParameters->RenderTargets = BasePassRenderTargets;
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PassParameters->RenderTargets.ShadingRateTexture = GVRSImageManager.GetVariableRateShadingImage(GraphBuilder, View, FVariableRateShadingImageManager::EVRSPassType::BasePass);
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const bool bShouldRenderView = View.ShouldRenderView();
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if (bShouldRenderView)
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{
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View.ParallelMeshDrawCommandPasses[EMeshPass::BasePass].BuildRenderingCommands(GraphBuilder, Scene->GPUScene, PassParameters->InstanceCullingDrawParams);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("BasePass"),
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PassParameters,
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ERDGPassFlags::Raster,
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[this, &View, PassParameters](FRHICommandList& RHICmdList)
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{
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SetStereoViewport(RHICmdList, View, 1.0f);
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View.ParallelMeshDrawCommandPasses[EMeshPass::BasePass].DispatchDraw(nullptr, RHICmdList, &PassParameters->InstanceCullingDrawParams);
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}
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);
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}
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const bool bShouldRenderViewForNanite = bNaniteEnabled && (!bDrawSceneViewsInOneNanitePass || ViewIndex == 0); // when bDrawSceneViewsInOneNanitePass, the first view should cover all the other atlased ones
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if (bShouldRenderViewForNanite)
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{
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// Should always have a full Z prepass with Nanite
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check(ShouldRenderPrePass());
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RenderNaniteBasePass(View, ViewIndex);
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}
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RenderEditorPrimitives(GraphBuilder, PassParameters, View, DrawRenderState, InstanceCullingManager);
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if (bShouldRenderView && View.Family->EngineShowFlags.Atmosphere)
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{
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FOpaqueBasePassParameters* SkyPassParameters = GraphBuilder.AllocParameters<FOpaqueBasePassParameters>();
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SkyPassParameters->BasePass = PassParameters->BasePass;
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SkyPassParameters->RenderTargets = BasePassRenderTargets;
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SkyPassParameters->View = View.GetShaderParameters();
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SkyPassParameters->ReflectionCapture = View.ReflectionCaptureUniformBuffer;
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View.ParallelMeshDrawCommandPasses[EMeshPass::SkyPass].BuildRenderingCommands(GraphBuilder, Scene->GPUScene, SkyPassParameters->InstanceCullingDrawParams);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("SkyPass"),
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SkyPassParameters,
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ERDGPassFlags::Raster,
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[this, &View, SkyPassParameters](FRHICommandList& RHICmdList)
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{
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SetStereoViewport(RHICmdList, View, 1.0f);
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View.ParallelMeshDrawCommandPasses[EMeshPass::SkyPass].DispatchDraw(nullptr, RHICmdList, &SkyPassParameters->InstanceCullingDrawParams);
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}
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);
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}
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}
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}
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```
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### SetDepthStencilStateForBasePass()
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```c++
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void SetDepthStencilStateForBasePass(
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FMeshPassProcessorRenderState& DrawRenderState,
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ERHIFeatureLevel::Type FeatureLevel,
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bool bDitheredLODTransition,
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const FMaterial& MaterialResource,
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bool bEnableReceiveDecalOutput,
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bool bForceEnableStencilDitherState)
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{
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const bool bMaskedInEarlyPass = (MaterialResource.IsMasked() || bDitheredLODTransition) && MaskedInEarlyPass(GShaderPlatformForFeatureLevel[FeatureLevel]);
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if (bEnableReceiveDecalOutput)
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{
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if (bMaskedInEarlyPass)
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{
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SetDepthStencilStateForBasePass_Internal<false, CF_Equal>(DrawRenderState, FeatureLevel);
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}
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else if (DrawRenderState.GetDepthStencilAccess() & FExclusiveDepthStencil::DepthWrite)
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{
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SetDepthStencilStateForBasePass_Internal<true, CF_GreaterEqual>(DrawRenderState, FeatureLevel);
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}
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else
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{
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SetDepthStencilStateForBasePass_Internal<false, CF_GreaterEqual>(DrawRenderState, FeatureLevel);
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}
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}
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else if (bMaskedInEarlyPass)
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{
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DrawRenderState.SetDepthStencilState(TStaticDepthStencilState<false, CF_Equal>::GetRHI());
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}
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if (bForceEnableStencilDitherState)
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{
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SetDepthStencilStateForBasePass_Internal<false, CF_Equal>(DrawRenderState, FeatureLevel);
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}
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}
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```
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## AnisotropyPass
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Anisotropy的RT设置：
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- RenderTarget：SceneTextures.GBufferF。
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- DepthStencil：SceneTextures.Depth.Target。**ERenderTargetLoadAction::ELoad**、**FExclusiveDepthStencil::DepthRead_StencilNop**
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### 管线状态
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在FAnisotropyMeshProcessor::CollectPSOInitializers()中：
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```c++
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ETextureCreateFlags GBufferFCreateFlags;
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EPixelFormat GBufferFPixelFormat = FSceneTextures::GetGBufferFFormatAndCreateFlags(GBufferFCreateFlags);
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AddRenderTargetInfo(GBufferFPixelFormat, GBufferFCreateFlags, RenderTargetsInfo);
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SetupDepthStencilInfo(PF_DepthStencil, SceneTexturesConfig.DepthCreateFlags, ERenderTargetLoadAction::ELoad,
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ERenderTargetLoadAction::ELoad, FExclusiveDepthStencil::DepthRead_StencilNop, RenderTargetsInfo);
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```
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```c++
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void SetupDepthStencilInfo(
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EPixelFormat DepthStencilFormat,
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ETextureCreateFlags DepthStencilCreateFlags,
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ERenderTargetLoadAction DepthTargetLoadAction,
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ERenderTargetLoadAction StencilTargetLoadAction,
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FExclusiveDepthStencil DepthStencilAccess,
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FGraphicsPipelineRenderTargetsInfo& RenderTargetsInfo)
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{
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// Setup depth stencil state
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RenderTargetsInfo.DepthStencilTargetFormat = DepthStencilFormat;
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RenderTargetsInfo.DepthStencilTargetFlag = DepthStencilCreateFlags;
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RenderTargetsInfo.DepthTargetLoadAction = DepthTargetLoadAction;
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RenderTargetsInfo.StencilTargetLoadAction = StencilTargetLoadAction;
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RenderTargetsInfo.DepthStencilAccess = DepthStencilAccess;
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const ERenderTargetStoreAction StoreAction = EnumHasAnyFlags(RenderTargetsInfo.DepthStencilTargetFlag, TexCreate_Memoryless) ? ERenderTargetStoreAction::ENoAction : ERenderTargetStoreAction::EStore;
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RenderTargetsInfo.DepthTargetStoreAction = RenderTargetsInfo.DepthStencilAccess.IsUsingDepth() ? StoreAction : ERenderTargetStoreAction::ENoAction;
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RenderTargetsInfo.StencilTargetStoreAction = RenderTargetsInfo.DepthStencilAccess.IsUsingStencil() ? StoreAction : ERenderTargetStoreAction::ENoAction;
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}
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```
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### ParallelRendering
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AnisotropyPass支持并行渲染，并行渲染的判断逻辑为
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```c++
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const bool bEnableParallelBasePasses = GRHICommandList.UseParallelAlgorithms() && CVarParallelBasePass.GetValueOnRenderThread();
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```
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看得出判断条件是：
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1. 显卡是否支持并行渲染。
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2. CVar（r.ParallelBasePass）是否开启并行渲染。
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从AnisotropyPass可以看得出并行渲染与一般渲染的差别在于：
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1. FRenderTargetBinding绑定时的ERenderTargetLoadAction不同，**并行为ELoad**；**普通渲染为EClear**。
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2. 调用AddPass添加了**ERDGPassFlags::SkipRenderPass**标记。
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3. 并行渲染会在AddPass中构建**FRDGParallelCommandListSet ParallelCommandListSet**，并作为传入**DispatchDraw**；普通渲染传递nullptr。
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4. 普通渲染会额外调用**SetStereoViewport(RHICmdList, View);**，本质是调用RHICmdList.SetViewport来设置View。
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### Code
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```c++
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RDG_CSV_STAT_EXCLUSIVE_SCOPE(GraphBuilder, RenderAnisotropyPass);
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SCOPED_NAMED_EVENT(FDeferredShadingSceneRenderer_RenderAnisotropyPass, FColor::Emerald);
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SCOPE_CYCLE_COUNTER(STAT_AnisotropyPassDrawTime);
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RDG_GPU_STAT_SCOPE(GraphBuilder, RenderAnisotropyPass);
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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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if (View.ShouldRenderView())
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{
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FParallelMeshDrawCommandPass& ParallelMeshPass = View.ParallelMeshDrawCommandPasses[EMeshPass::AnisotropyPass];
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if (!ParallelMeshPass.HasAnyDraw())
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{
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continue;
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}
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View.BeginRenderView();
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auto* PassParameters = GraphBuilder.AllocParameters<FAnisotropyPassParameters>();
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PassParameters->View = View.GetShaderParameters();
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PassParameters->RenderTargets.DepthStencil = FDepthStencilBinding(SceneTextures.Depth.Target, ERenderTargetLoadAction::ELoad, FExclusiveDepthStencil::DepthRead_StencilNop);
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ParallelMeshPass.BuildRenderingCommands(GraphBuilder, Scene->GPUScene, PassParameters->InstanceCullingDrawParams);
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if (bDoParallelPass)
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{
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AddClearRenderTargetPass(GraphBuilder, SceneTextures.GBufferF);
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PassParameters->RenderTargets[0] = FRenderTargetBinding(SceneTextures.GBufferF, ERenderTargetLoadAction::ELoad);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("AnisotropyPassParallel"),
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PassParameters,
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ERDGPassFlags::Raster | ERDGPassFlags::SkipRenderPass,
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[this, &View, &ParallelMeshPass, PassParameters](const FRDGPass* InPass, FRHICommandListImmediate& RHICmdList)
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{
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FRDGParallelCommandListSet ParallelCommandListSet(InPass, RHICmdList, GET_STATID(STAT_CLP_AnisotropyPass), View, FParallelCommandListBindings(PassParameters));
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ParallelMeshPass.DispatchDraw(&ParallelCommandListSet, RHICmdList, &PassParameters->InstanceCullingDrawParams);
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});
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}
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else
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{
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PassParameters->RenderTargets[0] = FRenderTargetBinding(SceneTextures.GBufferF, ERenderTargetLoadAction::EClear);
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GraphBuilder.AddPass(
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RDG_EVENT_NAME("AnisotropyPass"),
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PassParameters,
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ERDGPassFlags::Raster,
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[this, &View, &ParallelMeshPass, PassParameters](FRHICommandList& RHICmdList)
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{
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SetStereoViewport(RHICmdList, View);
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ParallelMeshPass.DispatchDraw(nullptr, RHICmdList, &PassParameters->InstanceCullingDrawParams);
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});
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}
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}
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}
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``` |