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03-UnrealEngine/卡通渲染相关资料/渲染功能/阴影控制/ToonShadow.md

@@ -901,6 +901,119 @@ void FDeferredShadingSceneRenderer::RenderDeferredShadowProjections(
 RenderShadowProjections():
 1. 取得当前FVisibleLightInfo、FLightSceneProxy；创建FProjectedShadowInfoArray DistanceFieldShadows、NormalShadows。
 2. 遍历VisibleLightInfo.ShadowsToProject，按照阴影特征将每个FProjectedShadowInfo加入DistanceFieldShadows、NormalShadows。
+3. 调用Lambda RenderNormalShadows()来渲染ScreenShadowMaskTexture与ScreenShadowMaskSubPixelTexture。
+4. 遍历DistanceFieldShadows，调用FProjectedShadowInfo->RenderRayTracedDistanceFieldProjection()来渲染距离场阴影。
+
+### FSceneRenderer::RenderShadowProjections()
+```c++
+void FSceneRenderer::RenderShadowProjections(
+	FRDGBuilder& GraphBuilder,
+	FRDGTextureRef OutputTexture,
+	const FMinimalSceneTextures& SceneTextures,
+	const FLightSceneProxy* LightSceneProxy,
+	TArrayView<const FProjectedShadowInfo* const> Shadows,
+	bool bSubPixelShadow,
+	bool bProjectingForForwardShading)
+{
+	CheckShadowDepthRenderCompleted();
+
+	for (int32 ViewIndex = 0; ViewIndex < Views.Num(); ViewIndex++)
+	{
+		const FViewInfo& View = Views[ViewIndex];
+		const FExclusiveDepthStencil ExclusiveDepthStencil = FExclusiveDepthStencil::DepthRead_StencilWrite;
+
+		if (bSubPixelShadow && !HairStrands::HasViewHairStrandsData(View))
+		{
+			continue;
+		}
+
+		View.BeginRenderView();
+
+		// Sanity check
+		if (bSubPixelShadow)
+		{
+			check(View.HairStrandsViewData.VisibilityData.HairOnlyDepthTexture);
+		}
+
+		FShadowProjectionPassParameters CommonPassParameters;
+		CommonPassParameters.SceneTextures = SceneTextures.GetSceneTextureShaderParameters(View.FeatureLevel);
+		CommonPassParameters.HairStrands = HairStrands::BindHairStrandsViewUniformParameters(View);
+
+		if (Strata::IsStrataEnabled())
+		{
+			CommonPassParameters.Strata = Strata::BindStrataGlobalUniformParameters(View);
+		}
+		
+		CommonPassParameters.RenderTargets[0] = FRenderTargetBinding(OutputTexture, ERenderTargetLoadAction::ELoad);
+		CommonPassParameters.RenderTargets.DepthStencil =
+			bSubPixelShadow ?
+			FDepthStencilBinding(View.HairStrandsViewData.VisibilityData.HairOnlyDepthTexture, ERenderTargetLoadAction::ELoad, ERenderTargetLoadAction::ELoad, ExclusiveDepthStencil) :
+			FDepthStencilBinding(SceneTextures.Depth.Target, ERenderTargetLoadAction::ELoad, ERenderTargetLoadAction::ELoad, ExclusiveDepthStencil);
+
+		RDG_GPU_MASK_SCOPE(GraphBuilder, View.GPUMask);
+		RDG_EVENT_SCOPE_CONDITIONAL(GraphBuilder, Views.Num() > 1, "View%d", ViewIndex);
+
+		// Project the shadow depth buffers onto the scene.
+		for (const FProjectedShadowInfo* ProjectedShadowInfo : Shadows)
+		{
+			if (ProjectedShadowInfo->bAllocated) 
+			{
+				// Only project the shadow if it's large enough in this particular view (split screen, etc... may have shadows that are large in one view but irrelevantly small in others)
+				if (ProjectedShadowInfo->FadeAlphas[ViewIndex] > 1.0f / 256.0f)
+				{
+					if (ProjectedShadowInfo->bOnePassPointLightShadow)
+					{
+						ProjectedShadowInfo->RenderOnePassPointLightProjection(GraphBuilder, CommonPassParameters, ViewIndex, View, LightSceneProxy, bProjectingForForwardShading, bSubPixelShadow);
+					}
+					else
+					{
+						ProjectedShadowInfo->RenderProjection(GraphBuilder, CommonPassParameters, ViewIndex, &View, LightSceneProxy, this, bProjectingForForwardShading, bSubPixelShadow);
+					}
+				}
+			}
+		}
+	}
+}
+```
+
+### Shader
+投射阴影渲染用Shader为：
+- ShadowProjectionVertexShader.usf
+	- FShadowProjectionNoTransformVS：直接输出顶点坐标。
+	- FShadowVolumeBoundProjectionVS：
+- ShadowProjectionPixelShader.usf
+	- TShadowProjectionPS
+	- TShadowProjectionFromTranslucencyPS
+	- TDirectionalPercentageCloserShadowProjectionPS
+	- TModulatedShadowProjection
+
+PS. 向往Blog： 以上可知，对ScreenShadowMaskTexture执行绘制时，是在屏幕空间进行的，并且ScreenShadowMask会被叠加多次（视光源的阴影实例个数而定），不同的通道存储了不同类型的阴影信息。
+
+## RenderLight()
+```c++
+// Render the light to the scene color buffer, conditionally using the attenuation buffer or a 1x1 white texture as input 
+if (bDirectLighting)
+{
+	for (int32 ViewIndex = 0, ViewCount = Views.Num(); ViewIndex < ViewCount; ++ViewIndex)
+	{
+		const FViewInfo& View = Views[ViewIndex];
+
+		// If the light elided the screen space shadow mask, sample directly from the packed shadow mask
+		int32 VirtualShadowMapId = INDEX_NONE;
+		if (bElideScreenShadowMask)
+		{
+			INC_DWORD_STAT(STAT_VSMLocalProjectionOnePassFast);
+			VirtualShadowMapId = VisibleLightInfo.GetVirtualShadowMapId(&View);
+		}
+
+		RDG_EVENT_SCOPE_CONDITIONAL(GraphBuilder, ViewCount > 1, "View%d", ViewIndex);
+		SCOPED_GPU_MASK(GraphBuilder.RHICmdList, View.GPUMask);
+		RenderLight(GraphBuilder, Scene, View, SceneTextures, &LightSceneInfo, VirtualShadowMapId != INDEX_NONE ? nullptr : ScreenShadowMaskTexture, LightingChannelsTexture, false /*bRenderOverlap*/, true /*bCloudShadow*/, VirtualShadowMapArray.GetUniformBuffer(), ShadowSceneRenderer->VirtualShadowMapMaskBits, VirtualShadowMapId);
+	}
+}
+```
+
+使用ScreenShadowMaskTexture来渲染阴影。
 
 # 半程阴影
 由晨风&Neverwind提出：