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

#define LPV_WRITE_SHADER	1

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

#include "LPVCommon.usf"

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

#define PROPOGATE_26TAP				1
#define PROPOGATE_USE_LDS			0
#define COMPRESSED_LDS_PROPOGATE	0

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

#define PACKED_VPL 1

struct Vpl
{
	float3 normal;
	float3 flux;
};

struct VplListEntry
{
#if PACKED_VPL
	uint	normalPacked;
	uint	fluxPacked;
#else
	float3	normal;
	float3  flux;
#endif

	int		nextIndex;
};

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

float3 UnpackVPLNormal( uint normalPacked )
{
	float3 n;
	n.x = float( ( normalPacked & 0x000000ff ) );
	n.y = float( ( normalPacked & 0x0000ff00 ) >> 8  );
	n.z = float( ( normalPacked & 0x00ff0000 ) >> 16 );
	return (n/254.0f)*2.0f-1.0f;
}

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

uint PackVPLNormal( float3 normal )
{
	uint3 n = uint3( (normal+1.0f) * 127.0f );
	return n.x | ( n.y << 8 ) | ( n.z << 16 );
}

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

Vpl UnpackVpl( VplListEntry entry )
{
	Vpl vpl;
#if PACKED_VPL
	vpl.flux   = UnpackRGY32( entry.fluxPacked );
	vpl.normal = UnpackVPLNormal( entry.normalPacked );
#else
	vpl.flux   = entry.flux;
	vpl.normal = entry.normal;
#endif
	return vpl;
}

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

VplListEntry PackVpl( Vpl vpl )
{
	VplListEntry entry;

#if PACKED_VPL
	entry.normalPacked	= PackVPLNormal( vpl.normal );
	entry.fluxPacked	= PackRGY32( vpl.flux );
#else
	entry.flux			= vpl.flux;
	entry.normal		= vpl.normal;
#endif
	return entry;
}

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

void AccumulateLighting(float3 colour, float3 n, float solidAngle, in out LPVCell cell ) 
{ 
	const float ONE_OVER_PI = 1.0f/3.1415927f;
	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;

	cell.coeffs[0] += colour*c0*solidAngle ;

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

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

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

#if LPV_WRITE_SHADER
void WriteLpvCell( in LPVCell cell, uint cellIndex )
{
	int3 texIndex = IndexToGridPos( cellIndex );

	gLpv3DTextureRW0[ texIndex ] = float4( cell.coeffs[0],     cell.AO ); // tex0.a is reserved for secondary occlusion;
	gLpv3DTextureRW1[ texIndex ] = float4( cell.coeffs[1].rgb, cell.coeffs[2].r );
	gLpv3DTextureRW2[ texIndex ] = float4( cell.coeffs[2].gb,  cell.coeffs[3].rg );
	gLpv3DTextureRW3[ texIndex ] = float4( cell.coeffs[3].b,   cell.coeffs[4].rgb );
	gLpv3DTextureRW4[ texIndex ] = float4( cell.coeffs[5].rgb, cell.coeffs[6].r );
	gLpv3DTextureRW5[ texIndex ] = float4( cell.coeffs[6].gb,  cell.coeffs[7].rg );
	gLpv3DTextureRW6[ texIndex ] = float4( cell.coeffs[7].b,   cell.coeffs[8].rgb );
}
#endif