/*
* All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
* its licensors.
*
* For complete copyright and license terms please see the LICENSE at the root of this
* distribution (the "License"). All use of this software is governed by the License,
* or, if provided, by the license below or the license accompanying this file. Do not
* remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*
*/

#include <Atom/Features/SrgSemantics.azsli>

#define THREADS 16

ShaderResourceGroup PassSrg : SRG_PerPass
{
    Texture2D<float> m_depthFullRes;
    RWTexture2D<float> m_depthHalfRes;
}

[numthreads(THREADS, THREADS, 1)]
void MainCS(uint3 dispatch_id: SV_DispatchThreadID)
{  
    uint2 targetPixel = dispatch_id.xy;

    // Take the upper left pixel in the 2x2 quad. This has two advantages:
    // 1) It gives us a real depth value instead of an averaged depth
    // 2) It preserves equal distance properties between pixels (necessary for SSAO)
    uint2 sourcePixel = targetPixel * 2;

    PassSrg::m_depthHalfRes[targetPixel] = PassSrg::m_depthFullRes[sourcePixel];
}