UnrealEngineUWP/Engine/Shaders/TranslucentLightingShaders.usf

// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.

/**
 * TranslucentLightingShaders.usf: Shaders for calculating lighting in a volume to use on translucency
 */

#include "Common.usf"
#include "SHCommon.usf"

#if INJECTION_PIXEL_SHADER
	#include "ShadowProjectionCommon.usf"
#endif

struct FWriteToSliceVertexOutput
{
	FScreenVertexOutput Vertex;
	uint LayerIndex : TEXCOORD1;
};

float4 UVScaleBias;
uint VolumeCascadeIndex;

/** Vertex shader that writes to a range of slices of a volume texture. */
void WriteToSliceMainVS(
	float2 InPosition : ATTRIBUTE0,
	float2 InUV       : ATTRIBUTE1,
	uint LayerIndex : SV_InstanceID,
	out FWriteToSliceVertexOutput Output
	)
{
	Output.Vertex.Position = float4( InPosition, 0, 1 );
	// Remap UVs based on the subregion of the volume texture being rendered to
    Output.Vertex.UV = InUV * UVScaleBias.xy + UVScaleBias.zw;
	Output.LayerIndex = LayerIndex;
}

void CopySceneAlphaMain(
	FScreenVertexOutput Input,
	out float OutAlpha : SV_Target0
	)
{
    OutAlpha = Texture2DSample(SceneColorTexture, SceneColorTextureSampler, Input.UV).a;
}

void CopySceneColorMain(
	FScreenVertexOutput Input,
	out float4 OutColor : SV_Target0
	)
{
    float4 LinearColor = Texture2DSample(SceneColorTexture, SceneColorTextureSampler, Input.UV);
	OutColor = float4(EncodeSceneColorForMaterialNode(LinearColor.rgb), 0);
}

/** Z index of the minimum slice in the range. */
int MinZ;

#if FEATURE_LEVEL >= FEATURE_LEVEL_SM4
/** Geometry shader that writes to a range of slices of a volume texture. */
[maxvertexcount(3)]
void WriteToSliceMainGS(triangle FWriteToSliceVertexOutput Input[3], inout TriangleStream<FWriteToSliceGeometryOutput> OutStream)
{
	FWriteToSliceGeometryOutput Vertex0;
	Vertex0.Vertex = Input[0].Vertex;
	Vertex0.LayerIndex = Input[0].LayerIndex + MinZ;

	FWriteToSliceGeometryOutput Vertex1;
	Vertex1.Vertex = Input[1].Vertex;
	Vertex1.LayerIndex = Input[1].LayerIndex + MinZ;

	FWriteToSliceGeometryOutput Vertex2;
	Vertex2.Vertex = Input[2].Vertex;
	Vertex2.LayerIndex = Input[2].LayerIndex + MinZ;

	OutStream.Append(Vertex0);
	OutStream.Append(Vertex1);
	OutStream.Append(Vertex2);
}

/** Filter pass inputs. */
Texture3D TranslucencyLightingVolumeAmbient;
SamplerState TranslucencyLightingVolumeAmbientSampler;
Texture3D TranslucencyLightingVolumeDirectional;
SamplerState TranslucencyLightingVolumeDirectionalSampler;

float TexelSize;

/** Filters the volume lighting to reduce aliasing. */
void FilterMainPS(
	FWriteToSliceGeometryOutput Input,
	out float4 OutColor0 : SV_Target0,
	out float4 OutColor1 : SV_Target1
	)
{
	float4 TextureValue0 = 0;
	float4 TextureValue1 = 0;

	float3 VolumeUV = float3(Input.Vertex.UV, (Input.LayerIndex + .5f) * TexelSize);

#define USE_FILTER 1

#if USE_FILTER

	// Use trilinear filtering to filter neighbors to the current voxel with minimal texture fetches
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(1, 1, 1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(-1, 1, 1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(1, -1, 1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(-1, -1, 1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(1, 1, -1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(-1, 1, -1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(1, -1, -1));
	TextureValue0 += Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV + .5f * TexelSize * float3(-1, -1, -1));

	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(1, 1, 1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(-1, 1, 1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(1, -1, 1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(-1, -1, 1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(1, 1, -1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(-1, 1, -1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(1, -1, -1));
	TextureValue1 += Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV + .5f * TexelSize * float3(-1, -1, -1));

	float InvWeight = 1.0f / 8;

#else

	TextureValue0 = Texture3DSample(TranslucencyLightingVolumeAmbient, TranslucencyLightingVolumeAmbientSampler, VolumeUV);
	TextureValue1 = Texture3DSample(TranslucencyLightingVolumeDirectional, TranslucencyLightingVolumeDirectionalSampler, VolumeUV);
	float InvWeight = 1;

#endif
	
	OutColor0 = TextureValue0 * InvWeight;
	OutColor1 = TextureValue1 * InvWeight;
}

#if INJECTION_PIXEL_SHADER

/** Parameters needed to access the shadow map of the light. */
float4x4 WorldToShadowMatrix;
float4 ShadowmapMinMax;

/** Pixel shader that calculates per object shadowing from translucency for a volume texture and outputs the shadow factor. */
void PerObjectShadowingMainPS(
	FWriteToSliceGeometryOutput Input,
	out float4 OutColor : SV_Target0
	)
{
	float ZPosition = View.TranslucencyLightingVolumeMin[VolumeCascadeIndex].z + (Input.LayerIndex + .5f) * View.TranslucencyLightingVolumeInvSize[VolumeCascadeIndex].w;
	float3 WorldPosition = float3(View.TranslucencyLightingVolumeMin[VolumeCascadeIndex].xy + Input.Vertex.UV / View.TranslucencyLightingVolumeInvSize[VolumeCascadeIndex].xy - .5f * View.TranslucencyLightingVolumeInvSize[VolumeCascadeIndex].w, ZPosition);
	float VoxelSize = View.TranslucencyLightingVolumeInvSize[VolumeCascadeIndex].w;

	float ShadowFactor = 1;

	float3 WorldPositionForShadowing = WorldPosition;
	// Transform the world position into shadowmap space
	float4 HomogeneousShadowPosition = mul(float4(WorldPositionForShadowing, 1), WorldToShadowMatrix);
	float2 ShadowUVs = HomogeneousShadowPosition.xy / HomogeneousShadowPosition.w;

	// Treat as unshadowed if the voxel is outside of the shadow map
	if (all(ShadowUVs >= ShadowmapMinMax.xy && ShadowUVs <= ShadowmapMinMax.zw))
	{
		ShadowFactor = CalculateTranslucencyShadowing(ShadowUVs, HomogeneousShadowPosition.z);
	}

	OutColor = float4(ShadowFactor.xxx, 0);
}

#endif // #if INJECTION_PIXEL_SHADER

#include "CubemapCommon.usf"

/** Add AmbientCubemap color to the volume. */
void InjectAmbientCubemapMainPS(
	FWriteToSliceGeometryOutput Input,
	out float4 OutColor : SV_Target0
	)
{
	// can be optimized by moving it into the vertex/geometry shader
	OutColor = float4(ComputeAmbientCubemapAvgColor(), 0);
}


#endif // FEATURE_LEVEL