UnrealEngineUWP/Engine/Shaders/LPVGeometryVolumeCommon.usf

//-----------------------------------------------------------------------------
// File:		LPVGeometryVolumeCommon.usf
//
// Summary:		Common functionality for geometry volumes
//
// Created:		2013-03-01
//
// Author:		mailto:benwood@microsoft.com
//
//				Copyright (C) Microsoft. All rights reserved.
//-----------------------------------------------------------------------------

#ifndef LPV_MULTIPLE_BOUNCES
#define LPV_MULTIPLE_BOUNCES 0
#endif 

//------------------------------------------------------------------------------

struct GeometryVolumeEntry
{
	float SH[9];
#if LPV_MULTIPLE_BOUNCES
	//@todo : store colour as SH? Is single component good enough?
	float3 color;
#endif
};

//------------------------------------------------------------------------------

#if LPV_GV_VOLUME_TEXTURE
RWTexture3D<float4>	gGv3DTextureRW0;
RWTexture3D<float4>	gGv3DTextureRW1;
RWTexture3D<float4>	gGv3DTextureRW2;

Texture3D<float4>	gGv3DTexture0;
Texture3D<float4>	gGv3DTexture1;
Texture3D<float4>	gGv3DTexture2;
#else
RWBuffer<float3>	gGvBufferRW;
Buffer<float3>		gGvBuffer;
#endif

//-------------------------------------------------------------------------------------------------
// Functions
//-------------------------------------------------------------------------------------------------

GeometryVolumeEntry ReadGvCell( uint index )
{
	GeometryVolumeEntry gv;

#if LPV_GV_VOLUME_TEXTURE
	int4 texIndex = int4( IndexToGridPos( index ), 0 );
	float4 gvTex0 = gGv3DTexture0.Load( texIndex );
	float4 gvTex1 = gGv3DTexture1.Load( texIndex );
	float4 gvTex2 = gGv3DTexture2.Load( texIndex );
	gv.SH[0] = gvTex0.x;
	gv.SH[1] = gvTex0.y;
	gv.SH[2] = gvTex0.z;
	gv.SH[3] = gvTex0.w;
	gv.SH[4] = gvTex1.x;
	gv.SH[5] = gvTex1.y;
	gv.SH[6] = gvTex1.z;
	gv.SH[7] = gvTex1.w;
	gv.SH[8] = gvTex2.x;
 #if LPV_MULTIPLE_BOUNCES
	gv.color = gvTex2.yzw;
 #endif
#else // LPV_GV_VOLUME_TEXTURE
 #if LPV_MULTIPLE_BOUNCES
	uint bufferIndex = index*4;
 #else
	uint bufferIndex = index*3;
 #endif
	[unroll]
	for ( uint i=0; i<3; i++ )
	{
		gv.SH[i*3]   = gGvBuffer[ bufferIndex+i ].x * 8.0 - 4.0;
		gv.SH[i*3+1] = gGvBuffer[ bufferIndex+i ].y * 8.0 - 4.0;
		gv.SH[i*3+2] = gGvBuffer[ bufferIndex+i ].z * 8.0 - 4.0;
	}
 #if LPV_MULTIPLE_BOUNCES
	gv.color = gGvBuffer[ bufferIndex+3 ].xyz;
 #endif
#endif // LPV_GV_VOLUME_TEXTURE


	return gv;
}

//-------------------------------------------------------------------------------------------------

void WriteGvCell( uint index, GeometryVolumeEntry entry )
{

#if LPV_GV_VOLUME_TEXTURE
	int3 texIndex = IndexToGridPos( index );
	gGv3DTextureRW0[ texIndex ] = float4( entry.SH[0], entry.SH[1], entry.SH[2], entry.SH[3] );
	gGv3DTextureRW1[ texIndex ] = float4( entry.SH[4], entry.SH[5], entry.SH[6], entry.SH[7] );
 #if LPV_MULTIPLE_BOUNCES
	gGv3DTextureRW2[ texIndex ] = float4( entry.SH[8], entry.color.rgb );
 #else
	gGv3DTextureRW2[ texIndex ] = float4( entry.SH[8], 0.0f, 0.0f, 0.0f );
 #endif

#else // LPV_GV_VOLUME_TEXTURE
 #if LPV_MULTIPLE_BOUNCES
	uint bufferIndex = index*4;
 #else
	uint bufferIndex = index*3;
 #endif

	[unroll]
	for ( uint i=0; i<3; i++ )
	{
		gGvBufferRW[ bufferIndex+i ] = float3( entry.SH[i*3], entry.SH[i*3+1], entry.SH[i*3+2] ) / 8.0 + 0.5;
	}

 #if LPV_MULTIPLE_BOUNCES
	gGvBufferRW[ bufferIndex+3 ].xyz = entry.color;
 #endif
#endif // LPV_GV_VOLUME_TEXTURE
}

//-------------------------------------------------------------------------------------------------

void ClearGvCell( uint index )
{ 
#if LPV_GV_VOLUME_TEXTURE
	int3 texIndex = IndexToGridPos( index );
	gGv3DTextureRW0[ texIndex ] = 0.0f;
	gGv3DTextureRW1[ texIndex ] = 0.0f;
	gGv3DTextureRW2[ texIndex ] = 0.0f;
#else // LPV_GV_VOLUME_TEXTURE
 #if LPV_MULTIPLE_BOUNCES
	uint bufferIndex = index*4;
 #else
	uint bufferIndex = index*3;
 #endif
	[unroll]
	for ( uint i=0; i<3; i++ ) gGvBufferRW[bufferIndex+i] = float3(0.5f,0.5f,0.5f);

 #if LPV_MULTIPLE_BOUNCES
	gGvBufferRW[ bufferIndex+3 ].xyz = float3(0.0f,0.0f,0.0f);
 #endif
#endif // LPV_GV_VOLUME_TEXTURE
}

//-------------------------------------------------------------------------------------------------

float SHLookupScalar( 
	float coeffs[9],
    float3 n ) 
{
	const float1 c1 = 0.429043 ;
	const float1 c2 = 0.511664 ;
	const float1 c3 = 0.743125 ;
	const float1 c4 = 0.886227 ;
	const float1 c5 = 0.247708 ;

	float3 n2 = n*n;
	float xy = n.x*n.y ; 
	float yz = n.y*n.z ; 
	float xz = n.x*n.z ;

	float value = c1*coeffs[8]*(n2.x-n2.y) + c3*coeffs[6]*n2.z + c4*coeffs[0] - c5*coeffs[6] 
            + 2.0f*c1*(coeffs[4]*xy + coeffs[7]*xz + coeffs[5]*yz) 
            + 2.0f*c2*(coeffs[3]*n.x+coeffs[1]*n.y+coeffs[2]*n.z) ;

	return max( value, 0.0f );
}

//-------------------------------------------------------------------------------------------------

void AccumulateCoeffsScalar(float value, float3 n, in out float coeffs[9] ) 
{ 
	const float c0 = 0.282095f;
	const float c1 = 0.488603f;
	const float c2 = 1.092548f;
	const float c3 = 0.315392f;
	const float c4 = 0.546274f;

	coeffs[0] += c0*value;

	coeffs[1] += (c1*n.y)*value;   
	coeffs[2] += (c1*n.z)*value;   
	coeffs[3] += (c1*n.x)*value;   

	coeffs[4] += (c2*n.x*n.y)*value; 
	coeffs[5] += (c2*n.y*n.z)*value; 
	coeffs[7] += (c2*n.x*n.z)*value; 
	coeffs[6] += (c3*(3.0f*n.z*n.z-1.0f))*value; 
	coeffs[8] += (c4*(n.x*n.x-n.y*n.y))*value;
}