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// Copyright © 2008- 2013 NVIDIA Corporation. All rights reserved.
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// #include "Common.fxh"

RW_Texture2D<float4> DestinationTex : register(u0);
Texture2D<float4> SourceTex : register(t0);

[NUM_THREADS(8,8,1)]
void main( uint2 group : S_GROUP_ID, uint2 thread : S_GROUP_THREAD_ID )
{
	uint2 dstIndex = group * 8 + thread;
	uint2 srcIndex = dstIndex * 2;

	uint width, height;
	SourceTex.GetDimensions(width, height);
	if(srcIndex.x >= width || srcIndex.y >= height)
		return;

	float4 x0 = SourceTex[srcIndex + uint2(0, 0)];
	float4 x1 = SourceTex[srcIndex + uint2(1, 0)];
	float4 x2 = SourceTex[srcIndex + uint2(0, 1)];
	float4 x3 = SourceTex[srcIndex + uint2(1, 1)];

	DestinationTex[dstIndex] = 0.25 * (x0 + x1 + x2 + x3);
}