BlueRoseNote/03-UnrealEngine/卡通渲染相关资料/渲染功能/ShaderModel/BasePass C++.md

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title	date	excerpt	tags	rating
Untitled	2024-09-26 18:41:24			⭐

RenderBasePass()

传入RenderBasePass()的DepthStencil逻辑如下：

const FExclusiveDepthStencil::Type BasePassDepthStencilAccess =  
    bAllowReadOnlyDepthBasePass  
    ? FExclusiveDepthStencil::DepthRead_StencilWrite  
    : FExclusiveDepthStencil::DepthWrite_StencilWrite;

FDeferredShadingSceneRenderer::RenderBasePass() => FDeferredShadingSceneRenderer::RenderBasePassInternal() =>

FBasePassMeshProcessor::TryAddMeshBatch =>

大致流程

1. 绑定GBuffer与Depth。

const FExclusiveDepthStencil ExclusiveDepthStencil(BasePassDepthStencilAccess);  
  
TStaticArray<FTextureRenderTargetBinding, MaxSimultaneousRenderTargets> BasePassTextures;  
uint32 BasePassTextureCount = SceneTextures.GetGBufferRenderTargets(BasePassTextures);  
Strata::AppendStrataMRTs(*this, BasePassTextureCount, BasePassTextures);  
TArrayView<FTextureRenderTargetBinding> BasePassTexturesView = MakeArrayView(BasePassTextures.GetData(), BasePassTextureCount);  
FRDGTextureRef BasePassDepthTexture = SceneTextures.Depth.Target;

2. GBuffer Clear

GraphBuilder.AddPass(RDG_EVENT_NAME("GBufferClear"), PassParameters, ERDGPassFlags::Raster,
			[PassParameters, ColorLoadAction, SceneColorClearValue](FRHICommandList& RHICmdList)
		{
			// If no fast-clear action was used, we need to do an MRT shader clear.
			if (ColorLoadAction == ERenderTargetLoadAction::ENoAction)
			{
				const FRenderTargetBindingSlots& RenderTargets = PassParameters->RenderTargets;
				FLinearColor ClearColors[MaxSimultaneousRenderTargets];
				FRHITexture* Textures[MaxSimultaneousRenderTargets];
				int32 TextureIndex = 0;

				RenderTargets.Enumerate([&](const FRenderTargetBinding& RenderTarget)
				{
					FRHITexture* TextureRHI = RenderTarget.GetTexture()->GetRHI();
					ClearColors[TextureIndex] = TextureIndex == 0 ? SceneColorClearValue : TextureRHI->GetClearColor();
					Textures[TextureIndex] = TextureRHI;
					++TextureIndex;
				});

				// Clear color only; depth-stencil is fast cleared.
				DrawClearQuadMRT(RHICmdList, true, TextureIndex, ClearColors, false, 0, false, 0);
			}
		});

SetDepthStencilStateForBasePass()

void SetDepthStencilStateForBasePass(
	FMeshPassProcessorRenderState& DrawRenderState,
	ERHIFeatureLevel::Type FeatureLevel,
	bool bDitheredLODTransition,
	const FMaterial& MaterialResource,
	bool bEnableReceiveDecalOutput,
	bool bForceEnableStencilDitherState)
{
	const bool bMaskedInEarlyPass = (MaterialResource.IsMasked() || bDitheredLODTransition) && MaskedInEarlyPass(GShaderPlatformForFeatureLevel[FeatureLevel]);
	if (bEnableReceiveDecalOutput)
	{
		if (bMaskedInEarlyPass)
		{
			SetDepthStencilStateForBasePass_Internal<false, CF_Equal>(DrawRenderState, FeatureLevel);
		}
		else if (DrawRenderState.GetDepthStencilAccess() & FExclusiveDepthStencil::DepthWrite)
		{
			SetDepthStencilStateForBasePass_Internal<true, CF_GreaterEqual>(DrawRenderState, FeatureLevel);
		}
		else
		{
			SetDepthStencilStateForBasePass_Internal<false, CF_GreaterEqual>(DrawRenderState, FeatureLevel);
		}
	}
	else if (bMaskedInEarlyPass)
	{
		DrawRenderState.SetDepthStencilState(TStaticDepthStencilState<false, CF_Equal>::GetRHI());
	}

	if (bForceEnableStencilDitherState)
	{
		SetDepthStencilStateForBasePass_Internal<false, CF_Equal>(DrawRenderState, FeatureLevel);
	}
}