o3de/Gems/AtomTressFX/Assets/Shaders/HairShortCutResolveDepth.azsl

/*
* Modifications Copyright (c) Contributors to the Open 3D Engine Project.
* For complete copyright and license terms please see the LICENSE at the root of this distribution.
*
* SPDX-License-Identifier: Apache-2.0 OR MIT
*
*/

//
// Copyright (c) 2019 Advanced Micro Devices, Inc. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
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#include <Atom/Features/SrgSemantics.azsli>

//!------------------------------ SRG Structure --------------------------------
//! Per pass SRG that holds the dynamic shared read-write buffer shared 
//! across all dispatches and draw calls. It is used for all the dynamic buffers
//! that can change between passes due to the application of skinning, simulation 
//! and physics affect. 
//! Once the compute pases are done, it is read by the rendering shaders.  
ShaderResourceGroup PassSrg : SRG_PerPass_WithFallback
{
    // Originally: [[vk::binding(0, 0)]] Texture2DArray<uint> FragmentDepthsTexture : register(t0, space0);
    Texture2DArray<uint>    m_fragmentDepthsTexture; 
}
//------------------------------------------------------------------------------

#include <HairFullScreenUtils.azsli>    // provides the Vertex Shader

//!=============================================================================
//!                 Resolve Depth - Second Pass of ShortCut
//! Full-screen pass that writes the farthest of the stored K near depths so it 
//! could be used for depth culling during the following geometry shading pass.
//!=============================================================================
float HairShortCutResolveDepthPS(VSOutput input) : SV_Depth
{
    // Blend the layers of fragments from back to front
    int2 vScreenAddress = int2(input.m_position.xy);

    // Write farthest depth value for culling in the next pass.
    // It may be the initial value of 1.0 if there were not enough fragments to write all depths, but then culling not important.
    const int farthestDepthIndex = 2;
    uint uDepth = PassSrg::m_fragmentDepthsTexture[uint3(vScreenAddress, farthestDepthIndex)];

    // The following line is writing the depth into the actual depth buffer
    return asfloat(uDepth);
}