// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "../Common.ush"
#include "../SceneData.ush"
#include "../WaveOpUtil.ush"
#include "NaniteRasterizer.ush"
#include "NaniteAttributeDecode.ush"
#include "../VirtualShadowMaps/VirtualShadowMapPageAccessCommon.ush"
#include "../VirtualShadowMaps/VirtualShadowMapPageOverlap.ush"
#include "NaniteWritePixel.ush"
#include "NaniteCullingCommon.ush"

// Material includes
#include "/Engine/Generated/Material.ush"
#include "NaniteVertexFactory.ush"

#if NANITE_TESSELLATION
#include "NaniteTessellation.ush"
#endif

#ifndef NANITE_TWO_SIDED
#define NANITE_TWO_SIDED 0
#endif

#define ENABLE_EARLY_Z_TEST (NANITE_PIXEL_PROGRAMMABLE)

// For shadows in displacement fallback raster bins, we need to apply minimum displacement on cluster triangles
#define ENABLE_FALLBACK_DISPLACEMENT (SHADOW_DEPTH_SHADER && ( \
	FIXED_DISPLACEMENT_FALLBACK || \
	(NANITE_VERTEX_PROGRAMMABLE && USES_DISPLACEMENT && !NANITE_TESSELLATION) \
))

#define MATERIAL_SHADER_HAS_DOMAIN (NANITE_TESSELLATION && (NANITE_VERTEX_PROGRAMMABLE || NANITE_PIXEL_PROGRAMMABLE))
#define MATERIAL_SHADER_HAS_DISPLACEMENT (ENABLE_FALLBACK_DISPLACEMENT || (MATERIAL_SHADER_HAS_DOMAIN && USES_DISPLACEMENT))

// State encompassing mapping a pixel position to memory address
struct FRaster
{
	float2	ViewportScale;
	float2	ViewportBias;
	int4	ScissorRect;

#if VIRTUAL_TEXTURE_TARGET
	uint2	pPage;
	uint2	vPage;
	float2	vTranslation;
	bool	bSinglePage;
	uint	ArrayIndex;
#endif
};

float4 CalculateSubpixelCoordinates( FRaster Raster, float4 PointClip )
{
	float4 Subpixel = float4( PointClip.xyz, 1 ) / PointClip.w;
	Subpixel.xy = Subpixel.xy * Raster.ViewportScale + Raster.ViewportBias;
	Subpixel.xy = floor(Subpixel.xy);
	return Subpixel;
}

float3 GetPerspectiveCorrectBarycentrics( float3 C, float3 InvW )
{
	float3 CInvW = C * InvW; // Perspective weighting by (1/w0, 1/w1, 1/w2)
	float3 UVW = CInvW * rcp(CInvW.x + CInvW.y + CInvW.z); // renormalize

	return UVW;
}

FBarycentrics CalculateBarycentrics( FRasterTri Tri, float3 C, bool bPerspectiveCorrectDerivatives )
{
	FBarycentrics Barycentrics = (FBarycentrics)0;

	const float3 UVW		= GetPerspectiveCorrectBarycentrics( C,	Tri.InvW );
	Barycentrics.Value		= UVW;

	BRANCH
	if( bPerspectiveCorrectDerivatives )
	{
		const float3 OffsetX	= { -Tri.Edge12.y, -Tri.Edge20.y, -Tri.Edge01.y };
		const float3 OffsetY	= {  Tri.Edge12.x,  Tri.Edge20.x,  Tri.Edge01.x };
		const float3 UVW_X		= GetPerspectiveCorrectBarycentrics( C + OffsetX,	Tri.InvW );
		const float3 UVW_Y		= GetPerspectiveCorrectBarycentrics( C + OffsetY,	Tri.InvW );
		Barycentrics.Value_dx	= UVW_X - UVW;
		Barycentrics.Value_dy	= UVW_Y - UVW;
	}
	else
	{
		Barycentrics.Value_dx	= Tri.Barycentrics_dx;
		Barycentrics.Value_dy	= Tri.Barycentrics_dy;
	}
	
	return Barycentrics;
}

int FindNthSetBit( uint Mask, int Index )
{
	int Last = countbits( Mask ) - Index - 1;

	uint p = 16;
	p += countbits( Mask >> p ) <= Last ? -8 : 8;
	p += countbits( Mask >> p ) <= Last ? -4 : 4;
	p += countbits( Mask >> p ) <= Last ? -2 : 2;
	p += countbits( Mask >> p ) <= Last ? -1 : 1;
	p  = countbits( Mask >> p ) == Last ? (p - 1) : p;
	return p;
}

int FindNthSetBit( uint2 Mask, int Index )
{
	int LowPop = countbits( Mask.x );
	return FindNthSetBit( Index < LowPop ? Mask.x : Mask.y, Index < LowPop ? Index : Index - LowPop ) + ( Index < LowPop ? 0 : 32 );
}

/*int FindNthSetBit_Scalar( uint Mask, int Index )
{
	return firstbitlow( WaveBallot( WavePrefixCountBits(x) == Index ) ) - 1;
	return firstbitlow( WaveBallot( MaskedBitCount( Mask ) == Index ) ) - 1;
}*/

uint MaskedBitCount2( uint2 Bits, uint Index )
{
	uint Mask = 1u << ( Index & 31 );
	Mask -= 1;

	uint A = Index < 32 ? Bits.x : Bits.y;
	uint B = Index < 32 ? 0 : countbits( Bits.x );

	return countbits( A & Mask ) + B;
}

groupshared uint GroupBaseVertIndex;
groupshared uint2 GroupUsedVertMask;
//groupshared uint GroupUniqueVertIndex[32];

void DeduplicateVertIndexes( uint3 VertIndexes, uint GroupThreadIndex, bool bTriValid, out uint OutNumUniqueVerts, out uint OutLaneVertIndex, out uint3 OutCornerLaneIndexes )
{
	const uint LaneCount = WaveGetLaneCount();

	// Calculate smallest active vertex
	uint BaseVertIndex;
	BRANCH
	if( LaneCount < 32 )
	{
		if (GroupThreadIndex == 0)
		{
			GroupBaseVertIndex = 0xFFFFFFFFu;
			GroupUsedVertMask = 0;
		}
		GroupMemoryBarrierWithGroupSync();
		if (bTriValid) WaveInterlockedMin(GroupBaseVertIndex, VertIndexes.x);	// VertIndexes.x is always smallest
		GroupMemoryBarrierWithGroupSync();
		BaseVertIndex = GroupBaseVertIndex;
	}
	else
	{
		BaseVertIndex = WaveActiveMin(bTriValid ? VertIndexes.x : 0xFFFFFFFFu);	// VertIndexes.x is always smallest
	}
	
	uint2 TriangleVertMask = 0;
	if( bTriValid )
	{
		VertIndexes -= BaseVertIndex;
	
		UNROLL
		for (uint i = 0; i < 3; i++)
		{
			bool bDstLow = VertIndexes[i] < 32;
			uint DstMask = 1u << ( VertIndexes[i] & 31 );

			if( bDstLow )
				TriangleVertMask.x |= DstMask;
			else
				TriangleVertMask.y |= DstMask;
		}
	}

	uint2 UsedVertMask = uint2(0,0);
	BRANCH
	if( LaneCount < 32 )
	{
		WaveInterlockedOr(GroupUsedVertMask.x, UsedVertMask.x);
		WaveInterlockedOr(GroupUsedVertMask.y, UsedVertMask.y);
		GroupMemoryBarrierWithGroupSync();
		UsedVertMask = GroupUsedVertMask;
	}
	else
	{
		UsedVertMask.x = WaveActiveBitOr(TriangleVertMask.x);
		UsedVertMask.y = WaveActiveBitOr(TriangleVertMask.y);
	}

	OutCornerLaneIndexes.x = MaskedBitCount(UsedVertMask, VertIndexes.x);
	OutCornerLaneIndexes.y = MaskedBitCount(UsedVertMask, VertIndexes.y);
	OutCornerLaneIndexes.z = MaskedBitCount(UsedVertMask, VertIndexes.z);

#if 0
	bool2 bIsUsed = ( UsedVertMask & (1u << GroupThreadIndex) ) != 0u;
	uint2 UsedPrefixSum =
	{
		MaskedBitCount( uint2( UsedVertMask.x, 0 ) ),
		MaskedBitCount( uint2( UsedVertMask.y, 0 ) ) + countbits( UsedVertMask.x )
	};

	if( bIsUsed.x )
		GroupUniqueVertIndex[ UsedPrefixSum.x ] = GroupThreadIndex;
	if( bIsUsed.y && UsedPrefixSum.y < 32 )
		GroupUniqueVertIndex[ UsedPrefixSum.y ] = GroupThreadIndex + 32;

	OutLaneVertIndex = GroupUniqueVertIndex[ GroupThreadIndex ] + BaseVertIndex;
#else
	OutLaneVertIndex = FindNthSetBit(UsedVertMask, GroupThreadIndex) + BaseVertIndex;
#endif
	OutNumUniqueVerts = CountBits(UsedVertMask);
}


// Only works for WaveSize >= 32 and only efficient for == 32.
// A sliding window approach like this relies on the index buffer being constrained such that a triangle
// can't referance a vertex >= window size back from the largest seen index so far in the index buffer.
// In addition the WaveSize must be at least as large as the window so that vertices referenced by triangles
// in this wave must either be present in the cache from the previous iteration (Lane0 - Window) or  in this iteration.
// Since we constrain to 32 when building the clusters the WaveSize that makes sense is the matching 32.
// Larger WaveSize could also work but the code would need to be changed.
template< typename FVertex >
struct TSlidingWindowVertexCache
{
	FVertex	CachedVert;
	uint	NumCached;
	bool	bFirstPass;

	FVertex	TriangleVerts[3];
	bool	TriangleVertsRead[3];

	void Init()
	{
		NumCached = 0;
		bFirstPass = true;
	}

	// Grab what's there for this triangle before updating cache. Otherwise cache would need to be double size.
	uint PullExisting( uint3 VertIndexes )
	{
		BRANCH
		if( !bFirstPass )
		{
			UNROLL
			for( uint k = 0; k < 3; k++ )
			{
				TriangleVerts[k] = WaveReadLaneAt( CachedVert, VertIndexes[k] & 31 );
				TriangleVertsRead[k] = VertIndexes[k] < NumCached;
			}
		}

		uint MaxVertIndex = max( VertIndexes.y, VertIndexes.z );
		uint WaveMaxVertIndex = WaveActiveMax( MaxVertIndex );
		uint NewNumCached = min( WaveMaxVertIndex + 1, NumCached + 32 );
	
		uint FirstUncachedLane = NumCached & 31;
		uint LaneVertIndex = ( WaveGetLaneIndex() - FirstUncachedLane ) & 31;
		LaneVertIndex += NumCached;
		NumCached = NewNumCached;

		return LaneVertIndex;
	}

	uint PullRemaining( uint3 VertIndexes )
	{
		UNROLL
		for( uint k = 0; k < 3; k++ )
		{
			BRANCH
			if( bFirstPass )
			{
				TriangleVerts[k] = WaveReadLaneAt( CachedVert, VertIndexes[k] & 31 );
			}
			else
			{
				FVertex TempVert = WaveReadLaneAt( CachedVert, VertIndexes[k] & 31 );
				if( !TriangleVertsRead[k] )
					TriangleVerts[k] = TempVert;
			}
		}
		bFirstPass = false;

		uint MaxVertIndex = max( VertIndexes.y, VertIndexes.z );
		uint InvalidMask = WaveBallot( MaxVertIndex >= NumCached ).x;
		uint NumTrisCached = InvalidMask ? firstbitlow( InvalidMask ) : 32;
		return NumTrisCached;
	}
};


struct FNullTranslation
{
	bool operator()( inout FVisBufferPixel Pixel )
	{
		return true;
	}
};

template< typename FSoftwareShader, typename FPageTranslation = FNullTranslation >
struct TNaniteWritePixel
{
	FRaster				Raster;
	FSoftwareShader		Shader;
	uint				PixelValue;
	uint2				VisualizeValues;
	FPageTranslation	PageTranslation;

	void operator()( uint2 PixelPos, float3 C, FRasterTri Tri )
	{
		float DeviceZ = Tri.DepthPlane.x + Tri.DepthPlane.y * C.y + Tri.DepthPlane.z * C.z;

		FVisBufferPixel Pixel = CreateVisBufferPixel( PixelPos, PixelValue, DeviceZ );
	
	#if VISUALIZE
		Pixel.VisualizeValues = VisualizeValues;
	#endif
	
	#if VIRTUAL_TEXTURE_TARGET
		Pixel.PhysicalPosition.xy = Pixel.Position;
		Pixel.PhysicalPosition.z = Raster.ArrayIndex;

		if( !PageTranslation( Pixel ) )
		{
			return;
		}
	#endif

		Pixel.WriteOverdraw();

	#if NANITE_PIXEL_PROGRAMMABLE && !NANITE_TESSELLATION

	#if ENABLE_EARLY_Z_TEST
		BRANCH
		if( !Pixel.EarlyDepthTest() )
		{
			return;
		}
	#endif

		FBarycentrics Barycentrics = CalculateBarycentrics( Tri, C, false );	// Perspective correct derivatives are not worth the effort for masked/PDO.

		float4 SvPosition = float4( Pixel.Position.xy + 0.5, Pixel.Depth, 1.0 );
	#if VIRTUAL_TEXTURE_TARGET
		// Translate it to virtual page
		SvPosition.xy = SvPosition.xy - Raster.vTranslation;
	#endif

		BRANCH
		if( !Shader.EvaluatePixel( Barycentrics, SvPosition, Tri.bBackFace, Pixel ) )
		{
			return;
		}
	#endif

		Pixel.Write();
	}
};


struct FMaterialShader
{
	FNaniteView					NaniteView;
	FPrimitiveSceneData 		PrimitiveData;
	FInstanceSceneData			InstanceData;
	FInstanceDynamicData		InstanceDynamicData;
	FCluster					Cluster;
	FVisibleCluster				VisibleCluster;
	FNaniteVertTransforms		VertTransforms;
	FNaniteTransformedVert		Verts[3];
	FMaterialVertexParameters	VertexParameters;

#if MATERIAL_SHADER_HAS_DISPLACEMENT
	FNaniteMaterialDisplacementParams	DisplacementParams;
	float								DisplacementFadeSlope;
	float								DisplacementFadeOffset;
#endif

	void InitVertexParameters(FNanitePostDeformVertex InputVert)
	{
	#if NANITE_VERTEX_PROGRAMMABLE || NANITE_PIXEL_PROGRAMMABLE
		// Should be Pow2(InvScale) but that requires renormalization
		float3x3 LocalToWorld = DFToFloat3x3(InstanceData.LocalToWorld);
		float3 InvScale = InstanceData.InvNonUniformScale;
		LocalToWorld[0] *= InvScale.x;
		LocalToWorld[1] *= InvScale.y;
		LocalToWorld[2] *= InvScale.z;

		VertexParameters = MakeInitializedMaterialVertexParameters();
		SetVertexParameterInstanceData(VertexParameters, InstanceData, PrimitiveData, true /* WPO */);
		SetVertexParameterAttributeData(VertexParameters, InputVert, InstanceDynamicData.LocalToTranslatedWorld, LocalToWorld, false /*bUsePrevPosition*/);

	#if ENABLE_NEW_HLSL_GENERATOR
		BRANCH
		if (IsFirstPerson_FromFlags(PrimitiveData.Flags) || (PrimitiveData.Flags & PRIMITIVE_SCENE_DATA_FLAG_EVALUATE_WORLD_POSITION_OFFSET) != 0u)
		{
			EvaluateVertexMaterialAttributes(VertexParameters);
		}
	#endif // ENABLE_NEW_HLSL_GENERATOR
	#endif
	}

#if NANITE_PIXEL_PROGRAMMABLE && NUM_TEX_COORD_INTERPOLATORS > 0
	void GetCustomizedUVs(inout float2 OutCustomizedUVs[NUM_TEX_COORD_INTERPOLATORS])
	{
		GetMaterialCustomizedUVs(VertexParameters, OutCustomizedUVs);
		GetCustomInterpolators(VertexParameters, OutCustomizedUVs);
	}
#endif

	float3 EvaluateWorldPositionOffset()
	{
		float3 WorldPositionOffset = 0.0f;
	#if NANITE_VERTEX_PROGRAMMABLE
		BRANCH
		if ((PrimitiveData.Flags & PRIMITIVE_SCENE_DATA_FLAG_EVALUATE_WORLD_POSITION_OFFSET) != 0u)
		{
			WorldPositionOffset = GetMaterialWorldPositionOffset(VertexParameters);
		}
	#endif
		return WorldPositionOffset;
	}

	void ApplyFirstPersonTransform(inout float3 TranslatedWorldPosition)
	{
		if (IsFirstPerson_FromFlags(PrimitiveData.Flags))
		{
			const float InterpolationAlpha = GetMaterialFirstPersonInterpolationAlpha(VertexParameters);
			TranslatedWorldPosition = lerp(TranslatedWorldPosition, mul(TranslatedWorldPosition, NaniteView.FirstPersonTransform), InterpolationAlpha);
		}
	}

#if MATERIAL_SHADER_HAS_DISPLACEMENT
	void InitDisplacement(FNaniteMaterialDisplacementParams InParams)
	{
		DisplacementParams = InParams;
	
	#if USES_DISPLACEMENT
		if (DisplacementParams.FadeSizeStop > 0.0f)
		{
			// Solve fade slope/offset relative to view depth
			// NOTE: This isn't the same as fading linearly with projected depth, but makes EvaluateDomain cheaper
			const float InstanceScale = InstanceData.NonUniformScale.w;
			const float MaxDisplacement = GetAbsMaxMaterialDisplacement( PrimitiveData );
			const float StartDepth = (MaxDisplacement * NaniteView.LODScale * InstanceScale) / DisplacementParams.FadeSizeStart;
			const float StopDepth = (MaxDisplacement * NaniteView.LODScale * InstanceScale) / DisplacementParams.FadeSizeStop;
			DisplacementFadeSlope = 1.0f / (StartDepth - StopDepth);
			DisplacementFadeOffset = -StopDepth * DisplacementFadeSlope;

			const bool bIsOrtho = NaniteView.ViewToClip[3][3] >= 1.0f;
			if (bIsOrtho)
			{
				// Displacement fade is uniform at all depths, so just solve it now rather than branch/condmask below
				DisplacementFadeOffset = saturate(DisplacementFadeSlope + DisplacementFadeOffset);
				DisplacementFadeSlope = 0.0f;
			}
		}
		else
	#endif
		{
			DisplacementFadeSlope = 0.0f;
			DisplacementFadeOffset = 1.0f;
		}
	}

	bool ApplyFallbackDisplacement(inout FNanitePostDeformVertex InOutVert)
	{
	#if ENABLE_FALLBACK_DISPLACEMENT
	#if FIXED_DISPLACEMENT_FALLBACK
		// We know that all clusters rasterized by this bin are displacement fallbacks, so save the extra check
		const bool bApplyDisplacement = true;
	#else
		const bool bApplyDisplacement = (VisibleCluster.Flags & NANITE_CULLING_FLAG_FALLBACK_RASTER) != 0 &&
			(PrimitiveData.PixelProgrammableDistanceSquared > 0.0f ||
			PrimitiveData.MaterialDisplacementFadeOutSize > 0.0f);
	#endif // FIXED_DISPLACEMENT_FALLBACK

		// For shadows in fixed function or fallback rasterization with WPO enabled, if we're rasterizing a cluster with
		// displacement disabled, apply minimum displacement to avoid shadowing objects that have displacement in the main
		// view	(prevents false self-shadow artifacts)
		if (bApplyDisplacement)
		{
			const float Displacement = -DisplacementParams.Center * DisplacementParams.Magnitude;
			InOutVert.Position += InOutVert.TangentBasis.TangentZ * Displacement;
			return true;
		}
	#endif // ENABLE_FALLBACK_DISPLACEMENT

		return false;
	}
#endif // MATERIAL_SHADER_HAS_DISPLACEMENT

#if MATERIAL_SHADER_HAS_DOMAIN
	float4 EvaluateDomain( float4 UVDensities, FBarycentrics Barycentrics )
	{
		float3 PointPostDeform = Lerp( 
			Verts[0].PointPostDeform,
			Verts[1].PointPostDeform,
			Verts[2].PointPostDeform,
			Barycentrics ).Value;

		float4 BaseClip = Lerp( 
			Verts[0].PointClip,
			Verts[1].PointClip,
			Verts[2].PointClip,
			Barycentrics ).Value;

		// Hopefully never used and will be dead code eliminated. TODO VT feedback needs this right now :(
		float4 SvPosition;
		SvPosition.xyz = BaseClip.xyz / BaseClip.w;
		SvPosition.xy = ( float2(0.5, -0.5) * SvPosition.xy + 0.5 ) * NaniteView.ViewSizeAndInvSize.xy + NaniteView.ViewRect.xy;
		SvPosition.w = 1;

		FVertexFactoryInterpolantsVSToPS Interpolants = (FVertexFactoryInterpolantsVSToPS)0;
		FMaterialPixelParameters MaterialParameters = FetchNaniteMaterialPixelParameters( PrimitiveData, InstanceData, InstanceDynamicData, VertTransforms, NaniteView, Verts, Cluster, Barycentrics, Interpolants, SvPosition );

		// Now we want to override UV derivatives to be based on uniform UV density so that there are no cracks
	#if NUM_TEX_COORD_INTERPOLATORS > 0
		for (uint TexCoordIndex = 0; TexCoordIndex < NUM_TEX_COORD_INTERPOLATORS; ++TexCoordIndex)
		{
			float2 Deriv = CalculateUVDerivativeForDomainPoint(
				NaniteView,
				BaseClip.w,
				InstanceData.NonUniformScale.w,
				UVDensities[TexCoordIndex] );
			MaterialParameters.TexCoords_DDX[TexCoordIndex] = Deriv;
			MaterialParameters.TexCoords_DDY[TexCoordIndex] = Deriv;
		}
	#endif

		FPixelMaterialInputs PixelMaterialInputs;
		CalcMaterialParametersEx(
			MaterialParameters,
			PixelMaterialInputs,
			SvPosition,
			MaterialParameters.ScreenPosition,
			true, // bIsFrontFace
			MaterialParameters.WorldPosition_CamRelative,
			MaterialParameters.WorldPosition_NoOffsets_CamRelative );

	#if USES_DISPLACEMENT
		// Determine Displacement with a distance fade based on depth
		float NormalizedDisplacement = GetMaterialDisplacement(PixelMaterialInputs);
		float DisplacementFade = saturate(BaseClip.w * DisplacementFadeSlope + DisplacementFadeOffset);

	#if DEPTH_ONLY // AKA Shadows
		if (DisplacementFade < 1.0f)
		{
			// Always push to the minimum displacement (instead of 0 displacement) for shadows to prevent self-shadowing
			// artifacts in the fade out region (more details above in ApplyFallbackDisplacement)
			NormalizedDisplacement = 0.0f;
			DisplacementFade = 1.0f;
		}
	#endif // DEPTH_ONLY

		const float Displacement = (NormalizedDisplacement - DisplacementParams.Center) * DisplacementParams.Magnitude * DisplacementFade;

	#if NANITE_TESSELLATION_NORMALIZE 
		float3 Normal = Lerp(
			Verts[0].NormalPostDeform,
			Verts[1].NormalPostDeform,
			Verts[2].NormalPostDeform,
			Barycentrics ).Value;
		Normal = normalize( Normal );

		PointPostDeform += Normal * Displacement;
	#else	// !NANITE_TESSELLATION_NORMALIZE
		float4 NormalClip = Lerp(
			Verts[0].NormalClip,
			Verts[1].NormalClip,
			Verts[2].NormalClip,
			Barycentrics).Value;

		float4 PointClip = BaseClip + NormalClip * Displacement;
	#endif	// NANITE_TESSELLATION_NORMALIZE
	#endif	// USES_DISPLACEMENT
		
	#if !(USES_DISPLACEMENT && !NANITE_TESSELLATION_NORMALIZE)
		float3 PointWorld = mul( float4( PointPostDeform, 1 ), InstanceDynamicData.LocalToTranslatedWorld ).xyz;
		float4 PointClip = mul( float4( PointWorld, 1 ), NaniteView.TranslatedWorldToClip );
	#endif

	#if NANITE_PIXEL_PROGRAMMABLE && MATERIALBLENDING_MASKED
		if( GetMaterialMask(PixelMaterialInputs) < 0.0 )
		{
			PointClip.z = -2.0;
			PointClip.w = -1.0;
		}
	#endif

		return PointClip;
	}
#endif

	bool EvaluatePixel( FBarycentrics Barycentrics, float4 SvPosition, bool bBackFace, inout FVisBufferPixel Pixel )
	{
		bool bValid = true;

#if NANITE_PIXEL_PROGRAMMABLE
		FVertexFactoryInterpolantsVSToPS Interpolants = (FVertexFactoryInterpolantsVSToPS)0;
	
		FMaterialPixelParameters MaterialParameters = FetchNaniteMaterialPixelParameters( PrimitiveData, InstanceData, InstanceDynamicData, VertTransforms, NaniteView, Verts, Cluster, Barycentrics, Interpolants, SvPosition );
		MaterialParameters.TwoSidedSign = bBackFace ? -1.0f : 1.0f;

		FPixelMaterialInputs PixelMaterialInputs;
		CalcMaterialParameters(MaterialParameters, PixelMaterialInputs, SvPosition, true /*bIsFrontFace*/);

		// NOTE: Disable PDO in shadow passes (it does undesirable things and has always been disabled in these passes in Unreal)
		// PDO with tessellation would screw up barycentrics.
	#if WANT_PIXEL_DEPTH_OFFSET && DEPTH_ONLY == 0 && !NANITE_TESSELLATION
		ApplyPixelDepthOffsetToMaterialParameters(MaterialParameters, PixelMaterialInputs, Pixel.Depth);
	#endif

	#if MATERIALBLENDING_MASKED
		bValid = GetDitheredMaterialMask(PixelMaterialInputs, SvPosition.xy, GetPrimaryView().StateFrameIndex) >= 0.0;
	#endif
#endif
		
		return bValid;
	}
};


#if VIRTUAL_TEXTURE_TARGET && NANITE_LATE_VSM_PAGE_TRANSLATION

groupshared uint GroupVsmPageTableCache[NANITE_VSM_PAGE_TABLE_CACHE_DIM * NANITE_VSM_PAGE_TABLE_CACHE_DIM];

void VsmPageTableStore(uint2 pPage, uint2 Coords)
{
	uint pPagePacked = (pPage.y << 16) | pPage.x;
	uint Index = Coords.y * NANITE_VSM_PAGE_TABLE_CACHE_DIM + Coords.x;
	GroupVsmPageTableCache[Index] = pPagePacked;
}

uint2 VsmPageTableLoad(uint2 Coords)
{
	uint Index = Coords.y * NANITE_VSM_PAGE_TABLE_CACHE_DIM + Coords.x;
	uint pPagePacked = GroupVsmPageTableCache[Index];
	return uint2(pPagePacked & 0xffff, pPagePacked >> 16);
}

void FetchAndCachePageTableEntry(FNaniteView NaniteView, uint2 vPageStart, uint2 vPageEnd, uint CacheIndex)
{
	uint2 CacheCoords = uint2(CacheIndex & 0x7, CacheIndex >> 3);
	if (all(vPageStart + CacheCoords <= vPageEnd))
	{
		FShadowPhysicalPage PhysicalPage = ShadowGetPhysicalPage( CalcPageOffset( NaniteView.TargetLayerIndex, NaniteView.TargetMipLevel, vPageStart + CacheCoords ) );
		uint2 pPageAddress = PhysicalPage.bThisLODValidForRendering ? PhysicalPage.PhysicalAddress : 0xffff;
		VsmPageTableStore(pPageAddress, CacheCoords);
	}
}

struct FCachedPageTable
{
	bool operator()( inout FVisBufferPixel Pixel )
	{
	#if VIRTUAL_TEXTURE_TARGET && NANITE_LATE_VSM_PAGE_TRANSLATION
		uint2 pPage = VsmPageTableLoad(Pixel.Position / VSM_PAGE_SIZE);
		if (pPage.x == 0xffff)
		{
			return false;
		}
		Pixel.PhysicalPosition.xy = pPage * VSM_PAGE_SIZE + (Pixel.Position & VSM_PAGE_SIZE_MASK);
	#endif
		return true;
	}
};

#endif // VIRTUAL_TEXTURE_TARGET &&  NANITE_LATE_VSM_PAGE_TRANSLATION

struct FFetchPageTable
{
	uint	MipLevel;
	FVirtualSMLevelOffset LevelOffset;

	bool operator()( inout FVisBufferPixel Pixel )
	{
	#if VIRTUAL_TEXTURE_TARGET
		if( !VirtualToPhysicalTexelForRendering( LevelOffset, MipLevel, Pixel.Position, Pixel.PhysicalPosition.xy ) )
		{
			// Not committed or should not be rendered into
			return false;
		}
	#endif
		return true;
	}
};

uint2 GetVisualizeValues(uint AddValue, uint SubPatch, uint MicroTri)
{
#if VISUALIZE
	uint VisualizeValueMax = 0;			// InterlockedMax64 using depth (value associated with surviving fragment)
	uint VisualizeValueAdd = AddValue;	// InterlockedAdd32 (value accumulated with every evaluated fragment)

#if NANITE_TESSELLATION
	VisualizeValueMax = 3; // Software Tessellation
#elif SOFTWARE_RASTER
	VisualizeValueMax = 2; // Software Raster
#else
	VisualizeValueMax = 1; // Hardware Raster
#endif

	VisualizeValueMax |= (SubPatch & 0xffu) << 8u;
	VisualizeValueMax |= (MicroTri & 0xffu) << 16u;

	return uint2(VisualizeValueMax, VisualizeValueAdd);
#else
	return 0;
#endif
}

uint2 GetVisualizeValues()
{
	return GetVisualizeValues(1u /* AddValue */, 0u /* SubPatch */, 0u /* MicroTri */);
}