//-----------------------------------------------------------------------------
// File:		LPVClear.usf
//
// Summary:		Shader to clear an LPV volume
//
// Created:		2013-03-01
//
// Author:		mailto:benwood@microsoft.com
//
//				Copyright (C) Microsoft. All rights reserved.
//-----------------------------------------------------------------------------

/*------------------------------------------------------------------------------
	Compile time parameters:
------------------------------------------------------------------------------*/

#include "Common.usf"
#include "LPVWriteCommon.usf" 
#include "LPVGeometryVolumeCommon.usf"

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

[numthreads(4,4,4)]
void CSClear(uint3 DTid : SV_DispatchThreadID) 
{
	uint i = GetGridAddress( DTid );

#if REFINE_OVER_TIME
	int3 idx = DTid;
	int3 scrollVec = int3(LpvWrite.mOldGridOffset) - int3(LpvWrite.mLpvGridOffset);
	idx += scrollVec;


	float maxExtent = MaxGridExtent( (float3)idx );
	float mul = PREV_FRAME_MULTIPLIER;
	if ( maxExtent > 15.5 )
	{
		mul = 0.0f;
	}

	idx = clamp( idx, int3(0,0,0), int3(31,31,31) );
	int sourceCell = GetGridAddress( idx );

	LPVCell cell = ReadLpvCell( sourceCell );

	mul *= LpvWrite.ClearMultiplier;

	//@TODO: add a separate shader for this
	[branch]
	if ( mul == 0.0f ) // This is needed in order to fix QNANs 
	{
		ClearCell( cell ); 
	}
	else
	{
		MultiplyCell( cell, mul );
	}

	WriteLpvCell( cell, i );

#else // !REFINE_OVER_TIME
	LPVCell cell;
	ClearCell( cell ); 
	WriteLpvCell( cell, i );
#endif
}

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

[numthreads(4,4,4)]
void CSClearGeometryVolume(uint3 DTid : SV_DispatchThreadID) 
{
	uint i = GetGridAddress( DTid );
	ClearGvCell( i );
}