Cache ray tracing instance mask and flags in Nanite FSceneProxy.

#rb Juan.Canada

[CL 15573733 by Yuriy ODonnell in ue5-main branch]

Engine/Source/Runtime/Engine/Private/RayTracingInstance.cpp

@@ -8,13 +8,24 @@
 
 #if RHI_RAYTRACING
 
+#include "RayTracingDefinitions.h"
+
 void FRayTracingInstance::BuildInstanceMaskAndFlags()
 {
 	TArrayView<const FMeshBatch> MeshBatches = GetMaterials();
+	FRayTracingMaskAndFlags MaskAndFlags = BuildRayTracingInstanceMaskAndFlags(MeshBatches);
+
+	Mask |= MaskAndFlags.Mask;
+	bForceOpaque = bForceOpaque || MaskAndFlags.bForceOpaque;
+}
+
+FRayTracingMaskAndFlags BuildRayTracingInstanceMaskAndFlags(TArrayView<const FMeshBatch> MeshBatches)
+{
+	FRayTracingMaskAndFlags Result;
 
 	ensureMsgf(MeshBatches.Num() > 0, TEXT("You need to add MeshBatches first for instance mask and flags to build upon."));
 
-	Mask = 0;
+	Result.Mask = 0;
 
 	bool bAllSegmentsOpaque = true;
 	bool bAnySegmentsCastShadow = false;
@@ -27,14 +38,16 @@ void FRayTracingInstance::BuildInstanceMaskAndFlags()
 		const FMaterialRenderProxy* FallbackMaterialRenderProxyPtr = nullptr;
 		const FMaterial& Material = MeshBatch.MaterialRenderProxy->GetMaterialWithFallback(ERHIFeatureLevel::SM5, FallbackMaterialRenderProxyPtr);
 		const EBlendMode BlendMode = Material.GetBlendMode();
-		Mask |= ComputeBlendModeMask(BlendMode);
+		Result.Mask |= ComputeBlendModeMask(BlendMode);
 		bAllSegmentsOpaque &= BlendMode == BLEND_Opaque;
 		bAnySegmentsCastShadow |= MeshBatch.CastRayTracedShadow && Material.CastsRayTracedShadows();
 		bAllSegmentsCastShadow &= MeshBatch.CastRayTracedShadow && Material.CastsRayTracedShadows();
 	}
 
-	bForceOpaque = bAllSegmentsOpaque && bAllSegmentsCastShadow;
-	Mask |= bAnySegmentsCastShadow ? RAY_TRACING_MASK_SHADOW : 0;
+	Result.bForceOpaque = bAllSegmentsOpaque && bAllSegmentsCastShadow;
+	Result.Mask |= bAnySegmentsCastShadow ? RAY_TRACING_MASK_SHADOW : 0;
+
+	return Result;
 }
 
 uint8 ComputeBlendModeMask(const EBlendMode BlendMode)

Engine/Source/Runtime/Engine/Private/RayTracingInstanceUtils.cpp

@@ -9,6 +9,7 @@
 
 #if RHI_RAYTRACING
 
+#include "RayTracingDefinitions.h"
 
 void AddOpaqueRaytracingInstance(const FMatrix& InstanceTransform, const FRayTracingGeometry* RayTracingGeometry, const uint32 Mask, TArray<FRayTracingInstance>& OutRayTracingInstances)
 {

Engine/Source/Runtime/Engine/Private/Rendering/NaniteResources.cpp

@@ -460,6 +460,9 @@ FSceneProxy::FSceneProxy(UStaticMeshComponent* Component)
 			RayTracingGeometry = &LODResources[LODIndex].RayTracingGeometry;
 			bHasRayTracingInstances = true;
 		}
+
+		// This will be filled later (on the render thread) and cached.
+		CachedRayTracingInstanceMaskAndFlags.Mask = 0;
 	}
 #endif
 }
@@ -951,7 +954,13 @@ void FSceneProxy::GetDynamicRayTracingInstances(FRayTracingMaterialGatheringCont
 
 	RayTracingInstance.MaterialsView = CachedRayTracingMaterials;
 
-	RayTracingInstance.BuildInstanceMaskAndFlags();
+	if (CachedRayTracingInstanceMaskAndFlags.Mask == 0)
+	{
+		CachedRayTracingInstanceMaskAndFlags = BuildRayTracingInstanceMaskAndFlags(CachedRayTracingMaterials);
+	}
+
+	RayTracingInstance.Mask = CachedRayTracingInstanceMaskAndFlags.Mask;
+	RayTracingInstance.bForceOpaque = CachedRayTracingInstanceMaskAndFlags.bForceOpaque;
 }
 #endif
 

Engine/Source/Runtime/Engine/Public/NaniteSceneProxy.h

@@ -6,6 +6,7 @@
 #include "PrimitiveSceneProxy.h"
 #include "PrimitiveViewRelevance.h"
 #include "Rendering/NaniteResources.h"
+#include "RayTracingInstance.h"
 
 namespace Nanite
 {
@@ -163,6 +164,7 @@ protected:
 	TArray<FMatrix> CachedRayTracingInstanceTransforms;
 	TArray<FMeshBatch> CachedRayTracingMaterials;
 	FMatrix CachedRayTracingInstanceLocalToWorld = {};
+	FRayTracingMaskAndFlags CachedRayTracingInstanceMaskAndFlags;
 #endif
 
 #if NANITE_ENABLE_DEBUG_RENDERING

Engine/Source/Runtime/Engine/Public/RayTracingInstance.h

@@ -6,7 +6,15 @@
 #include "MeshBatch.h"
 
 #if RHI_RAYTRACING
-#include "RayTracingDefinitions.h"
+
+struct FRayTracingMaskAndFlags
+{
+	/** Instance mask that can be used to exclude the instance from specific effects (eg. ray traced shadows). */
+	uint8 Mask = 0xFF;
+
+	/** Whether the instance is forced opaque, i.e. anyhit shaders are disabled on this instance */
+	bool bForceOpaque = false;
+};
 
 struct FRayTracingInstance
 {
@@ -42,10 +50,10 @@ struct FRayTracingInstance
 	}
 
 	/** Whether the instance is forced opaque, i.e. anyhit shaders are disabled on this instance */
-	bool bForceOpaque : 1;
+	bool bForceOpaque = false;
 
 	/** Instance mask that can be used to exclude the instance from specific effects (eg. ray traced shadows). */
-	uint8 Mask = RAY_TRACING_MASK_ALL;
+	uint8 Mask = 0xFF;
 
 	/** 
 	* Transforms count. When NumTransforms == 1 we create a single instance. 
@@ -86,5 +94,7 @@ struct FRayTracingInstance
 	ENGINE_API void BuildInstanceMaskAndFlags();
 };
 
+/** Build mask and flags based on materials specified in Materials. You can still override Mask after calling this function. */
+ENGINE_API FRayTracingMaskAndFlags BuildRayTracingInstanceMaskAndFlags(TArrayView<const FMeshBatch> MeshBatches);
 ENGINE_API uint8 ComputeBlendModeMask(const EBlendMode BlendMode);
 #endif