o3de/Gems/Meshlets/Assets/Shaders/MeshletsPerObjectRenderSrg.azsli

/*
 * 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
 *
 */

#pragma once

#include <scenesrg_all.srgi>

/*
// Utilize the following PerDraw srg for instancing - currently not used yet.
ShaderResourceGroup MeshletsInstanceRenderSrg : SRG_PerDraw
{
    //! used object Id for instancing and matrix retrieval
    uint m_objectId;

    //! Returns the matrix for transforming points from Object Space to World Space.
    float4x4 GetWorldMatrix()
    {
        return SceneSrg::GetObjectToWorldMatrix(m_objectId);
    }

    //! Returns the inverse-transpose of the world matrix.
    //! Commonly used to transform normals while supporting non-uniform scale.
    float3x3 GetWorldMatrixInverseTranspose()
    {
        return SceneSrg::GetObjectToWorldInverseTransposeMatrix(m_objectId);
    }
}
*/

ShaderResourceGroup MeshletsObjectRenderSrg : SRG_PerObject
{
    //--------------------------------------------------
    // This part should be moved outside the PerObject srg and used in the PerDraw 
    // srg that represents the instance frequency.
    // object Id is used as an index for instancing and matrix retrieval in the 
    // SceneSrg matrices arrays.
    uint m_objectId;

    //! Returns the matrix for transforming points from Object Space to World Space.
    float4x4 GetWorldMatrix()
    {
        return SceneSrg::GetObjectToWorldMatrix(m_objectId);
    }

    //! Returns the inverse-transpose of the world matrix.
    //! Commonly used to transform normals while supporting non-uniform scale.
    float3x3 GetWorldMatrixInverseTranspose()
    {
        return SceneSrg::GetObjectToWorldInverseTransposeMatrix(m_objectId);
    }

    //---------------------------------------------------
    // Vertex streams - currently we use Buffer<float> instead of the exact required
    // data type (float3 for example) because of alignment problem in Atom buffer 
    // creation from a common pool.
    // [To Do] - change when supported to prevent offset calculation overhead.
//    Buffer<float3> m_positions;
//    Buffer<float3> m_normals;
//    Buffer<float4> m_tangents; 
//    Buffer<float3> m_bitangents; 

    Buffer<float> m_positions;
    Buffer<float> m_normals;
    Buffer<float4> m_tangents; 
    Buffer<float> m_bitangents; 

    Buffer<float2> m_uvs;

    float3 GetPosition(uint vertexIndex)
    {
        uint index = vertexIndex * 3;
        return float3(m_positions[index], m_positions[index+1], m_positions[index+2]);
    }

    float3 GetNormal(uint vertexIndex)
    {
        uint index = vertexIndex * 3;
        return float3(m_normals[index], m_normals[index+1], m_normals[index+2]);
    }

    float3 GetBiTangent(uint vertexIndex)
    {
        uint index = vertexIndex * 3;
        return float3(m_bitangents[index], m_bitangents[index+1], m_bitangents[index+2]);
    }

    // The last element of the tangents indicates face direction / winding
    float4 GetTangent(uint vertexIndex)
    {
        return m_tangents[vertexIndex];
    }

    float2 GetUV(uint vertexIndex)
    {
        return m_uvs[vertexIndex];
    }
}