Mesh Shader pipeline API overview

typedef  enum D3D12_FEATURE {
    ...
    D3D12_FEATURE_D3D12_OPTIONS7,
} D3D12_FEATURE;

typedef enum D3D12_MESH_SHADER_TIER
{
    D3D12_MESH_SHADER_TIER_NOT_SUPPORTED,
    D3D12_MESH_SHADER_TIER_1
} D3D12_MESH_SHADER_TIER;

typedef struct D3D12_FEATURE_DATA_D3D12_OPTIONS7 
{
    _Out_  D3D12_MESH_SHADER_TIER       MeshShaderTier;
    _Out_  D3D12_SAMPLER_FEEDBACK_TIER  SamplerFeedbackTier;
} D3D12_FEATURE_DATA_D3D12_OPTIONS7;

HRESULT ID3D12Device::CheckFeatureSupport(
  D3D12_FEATURE Feature,
  void*         pFeatureSupportData,
  UINT          FeatureSupportDataSize
);

typedef struct D3D12_PIPELINE_STATE_STREAM_DESC {
    _In_  SIZE_T SizeInBytes;
    _In_  void*  pPipelineStateSubobjectStream;
} D3D12_PIPELINE_STATE_STREAM_DESC;

HRESULT ID3D12Device2::CreatePipelineState(
    const D3D12_PIPELINE_STATE_STREAM_DESC* pDesc,
    REFIID                                  riid,
    void**                                  ppPipelineState
);

void ID3D12GraphicsCommandList::DispatchMesh(uint groupCountX, uint groupCountY, uint groupCountZ);

typedef enum D3D12_INDIRECT_ARGUMENT_TYPE {
    ...
    D3D12_INDIRECT_ARGUMENT_TYPE_DISPATCH_MESH
} D3D12_INDIRECT_ARGUMENT_TYPE;

typedef struct D3D12_INDIRECT_ARGUMENT_DESC
{
    D3D12_INDIRECT_ARGUMENT_TYPE Type; // = D3D12_INDIRECT_ARGUMENT_TYPE_DISPATCH_MESH
    union 
    {
        ...
        struct 
        {
            UINT ThreadGroupCountX;
            UINT ThreadGroupCountY;
            UINT ThreadGroupCountZ;
        } D3D12_DISPATCH_MESH_ARGUMENTS;
    }
} D3D12_INDIRECT_ARGUMENT_DESC;

void ID3D12GraphicsCommandList::ExecuteIndirect(
    ID3D12CommandSignature* pCommandSignature,
    UINT                    MaxCommandCount,
    ID3D12Resource*         pArgumentBuffer,
    UINT64                  ArgumentBufferOffset,
    ID3D12Resource*         pCountBuffer,
    UINT64                  CountBufferOffset
);

struct MyPsoStreamDesc
{
    CD3DX12_PIPELINE_STATE_STREAM_ROOT_SIGNATURE        pRootSignature;
    CD3DX12_PIPELINE_STATE_STREAM_AS                    AS;
    CD3DX12_PIPELINE_STATE_STREAM_MS                    MS;
    CD3DX12_PIPELINE_STATE_STREAM_PS                    PS;
    CD3DX12_PIPELINE_STATE_STREAM_BLEND_DESC            BlendState;
    CD3DX12_PIPELINE_STATE_STREAM_DEPTH_STENCIL1        DepthStencilState;
    CD3DX12_PIPELINE_STATE_STREAM_RASTERIZER            RasterizerState;
    CD3DX12_PIPELINE_STATE_STREAM_RENDER_TARGET_FORMATS RTFormats;
    CD3DX12_PIPELINE_STATE_STREAM_DEPTH_STENCIL_FORMAT  DepthFormat;
    CD3DX12_PIPELINE_STATE_STREAM_SAMPLE_DESC           SampleDesc;
    CD3DX12_PIPELINE_STATE_STREAM_SAMPLE_MASK           SampleMask;
}

void CreatePipelineState(ID3D12Device* d3dDevice)
{
    // Check Mesh Shader pipeline feature support.
    D3D12_FEATURE_DATA_D3D12_OPTIONS7 options;
    device->CheckFeatureSupport(D3D12_FEATURE_D3D12_OPTIONS7, &options, sizeof(options));

    if (options.MeshShaderTier == D3D12_MESH_SHADER_TIER_NOT_SUPPORTED)
        throw std::exception("Mesh Shaders not supported!"); 

    // Set up PSO Stream Desc.
    MyPsoStreamDesc psoDesc;
    psoDesc.AS = D3D12_SHADER_BYTECODE{ ... };
    psoDesc.MS = D3D12_SHADER_BYTECODE{ ... };
    ...

    // Create Pipeline State Object with stream desc.
    D3D12_PIPELINE_STATE_STREAM_DESC desc = { sizeof(psoDesc), &psoDesc };
    device->CreatePipelineState(&desc, IID_PPV_ARGS(&msPso));
}

void Draw(ID3D12GraphicsCommandList* commandList)
{
    // Set up pipeline and root signature parameters.
    commandList->SetPipelineState(&msPso);
    commandList->SetGraphicsRootSignature(&msRootSig);
    ...

    // Dispatch threadgroups.
    commandList->DispatchMesh(someGroupCount, 1, 1);
}