o3de/Gems/AtomTressFX/Assets/Shaders/HairSimulationComputeSrgs.azsli

/*
 * 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.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//------------------------------------------------------------------------------
// File: HairSimulationComputeSrgs.azsli
//
// Declarations of SRGs used by the hair shaders.
//------------------------------------------------------------------------------
#pragma once

#include <HairComputeSrgs.azsli>

//!-----------------------------------------------------------------------------
//! 
//!                    Skinning / Simulation Render Usage
//!         Per Objects Space 0 - Static Buffers for Hair Generation
//! 
//! ----------------------------------------------------------------------------
struct TressFXSimulationParams
{
    float4 m_Wind;
    float4 m_Wind1;
    float4 m_Wind2;
    float4 m_Wind3;
           
    float4 m_Shape;         // damping, local stiffness, global stiffness, global range.
    float4 m_GravTimeTip;   // gravity maginitude (assumed to be in negative y direction.)
    int4   m_SimInts;       // Length iterations, local iterations, collision flag.
    int4   m_Counts;        // num strands per thread group, num follow hairs per guid hair, num verts per strand.
    float4 m_VSP;           // VSP parameters - controls how Velocity Shock Propogation will dictate how 
                            // fast velocities are handled and can be compensated using the hair root velocity  

    float m_ResetPositions;
    float m_ClampPositionDelta;
    float m_pad1;
    float m_pad2;

#if TRESSFX_DQ  // this option is currently not functional 
    float4 m_BoneSkinningDQ[AMD_TRESSFX_MAX_NUM_BONES * 2];
#else
    row_major float4x4 m_BoneSkinningMatrix[AMD_TRESSFX_MAX_NUM_BONES];
#endif
};

struct BoneSkinningData
{
    float4 boneIndex;  // x, y, z and w component are four bone indices per strand
    float4 boneWeight; // x, y, z and w component are four bone weights per strand
};

//!------------------------------ SRG Structure --------------------------------
//! This is the static Srg required for the hair genration per hair object draw.  
//! The data is used only for skinning / simulation and doesn't change between 
//!  the object's passes.
//! To match to the original TressFX naming follow the global defines bellow.
ShaderResourceGroup HairGenerationSrg : SRG_PerDraw
{
    // Buffers containing hair generation properties.
    Buffer<float4>                      m_initialHairPositions;
    Buffer<float>                       m_hairRestLengthSRV;
    Buffer<float>                       m_hairStrandType;
    Buffer<float4>                      m_followHairRootOffset;
    StructuredBuffer<BoneSkinningData>  m_boneSkinningData;

    // Constant buffer structure reflected in code as 'TressFXSimulationParams' 
    TressFXSimulationParams             m_tressfxSimParameters; 
};

//------------------------------------------------------------------------------
// Allow for the code to run with minimal changes - compute passes usage

#define g_InitialHairPositions    HairGenerationSrg::m_initialHairPositions
#define g_HairRestLengthSRV       HairGenerationSrg::m_hairRestLengthSRV
#define g_HairStrandType          HairGenerationSrg::m_hairStrandType

#define g_FollowHairRootOffset    HairGenerationSrg::m_followHairRootOffset
#define g_BoneSkinningData        HairGenerationSrg::m_boneSkinningData

#define g_NumOfStrandsPerThreadGroup      HairGenerationSrg::m_tressfxSimParameters.m_Counts.x
#define g_NumFollowHairsPerGuideHair      HairGenerationSrg::m_tressfxSimParameters.m_Counts.y
#define g_NumVerticesPerStrand            HairGenerationSrg::m_tressfxSimParameters.m_Counts.z

#define g_NumLocalShapeMatchingIterations HairGenerationSrg::m_tressfxSimParameters.m_SimInts.y

#define g_GravityMagnitude                HairGenerationSrg::m_tressfxSimParameters.m_GravTimeTip.x
#define g_TimeStep                        HairGenerationSrg::m_tressfxSimParameters.m_GravTimeTip.y
#define g_TipSeparationFactor             HairGenerationSrg::m_tressfxSimParameters.m_GravTimeTip.z

#define g_Wind HairGenerationSrg::m_tressfxSimParameters.m_Wind
#define g_Wind1 HairGenerationSrg::m_tressfxSimParameters.m_Wind1
#define g_Wind2 HairGenerationSrg::m_tressfxSimParameters.m_Wind2
#define g_Wind3 HairGenerationSrg::m_tressfxSimParameters.m_Wind3
#define g_ResetPositions HairGenerationSrg::m_tressfxSimParameters.m_ResetPositions
#define g_ClampPositionDelta HairGenerationSrg::m_tressfxSimParameters.m_ClampPositionDelta
#define g_BoneSkinningDQ HairGenerationSrg::m_tressfxSimParameters.m_BoneSkinningDQ
#define g_BoneSkinningMatrix HairGenerationSrg::m_tressfxSimParameters.m_BoneSkinningMatrix

// We no longer support groups (indirection).
int GetStrandType(int globalThreadIndex)
{
    return 0;
}

float GetDamping(int strandType)
{
    // strand type unused.
    // In the future, we may create an array and use indirection.
    return HairGenerationSrg::m_tressfxSimParameters.m_Shape.x;
}

float GetLocalStiffness(int strandType)
{
    // strand type unused.
    // In the future, we may create an array and use indirection.
    return HairGenerationSrg::m_tressfxSimParameters.m_Shape.y;
}

float GetGlobalStiffness(int strandType)
{
    // strand type unused.
    // In the future, we may create an array and use indirection.
    return HairGenerationSrg::m_tressfxSimParameters.m_Shape.z;
}

float GetGlobalRange(int strandType)
{
    // strand type unused.
    // In the future, we may create an array and use indirection.
    return HairGenerationSrg::m_tressfxSimParameters.m_Shape.w;
}

float GetVelocityShockPropogation()
{
    return HairGenerationSrg::m_tressfxSimParameters.m_VSP.x;
}

float GetVSPAccelThreshold()
{
    return HairGenerationSrg::m_tressfxSimParameters.m_VSP.y;
}

int GetLocalConstraintIterations()
{
    return (int)HairGenerationSrg::m_tressfxSimParameters.m_SimInts.y;
}

int GetLengthConstraintIterations()
{
    return (int)HairGenerationSrg::m_tressfxSimParameters.m_SimInts.x;
}
//------------------------------------------------------------------------------