创建描述符

描述并显示创建以下内容的示例：索引、顶点和常量缓冲区视图；着色器资源、呈现器目标、无序访问、流输出和深度模具视图；以及采样器。 创建描述符的所有方法都是自由线程。

索引缓冲区视图

要创建索引缓冲区视图，请填写 D3D12_INDEX_BUFFER_VIEW 结构：

typedef struct D3D12_INDEX_BUFFER_VIEW
{
    D3D12_GPU_VIRTUAL_ADDRESS BufferLocation;
    UINT SizeInBytes;
    DXGI_FORMAT Format;
}   D3D12_INDEX_BUFFER_VIEW;

设置缓冲区的位置（调用 GetGPUVirtualAddress）和大小，并请注意，D3D12_GPU_VIRTUAL_ADDRESS 的定义如下所示：

typedef UINT64 D3D12_GPU_VIRTUAL_ADDRESS;

请参阅 DXGI_FORMAT 枚举。 通常，索引缓冲区可能会采用以下定义：

const DXGI_FORMAT StandardIndexFormat = DXGI_FORMAT_R32_UINT;

最后调用 ID3D12GraphicsCommandList::IASetIndexBuffer。

例如，

// Initialize the index buffer view.
m_indexBufferView.BufferLocation = m_indexBuffer->GetGPUVirtualAddress();
m_indexBufferView.SizeInBytes = SampleAssets::IndexDataSize;
m_indexBufferView.Format = SampleAssets::StandardIndexFormat;

顶点缓冲区视图

要创建顶点缓冲区视图，请填写 D3D12_VERTEX_BUFFER_VIEW 结构：

typedef struct D3D12_VERTEX_BUFFER_VIEW {
    D3D12_GPU_VIRTUAL_ADDRESS BufferLocation;  
    UINT SizeInBytes;  
    UINT StrideInBytes;  
} D3D12_VERTEX_BUFFER_VIEW;

设置缓冲区的位置（调用 GetGPUVirtualAddress）和大小，并请注意，D3D12_GPU_VIRTUAL_ADDRESS 的定义如下所示：

typedef UINT64 D3D12_GPU_VIRTUAL_ADDRESS;

步幅通常是单个顶点数据结构的大小，例如 sizeof(Vertex);。 然后调用 ID3D12GraphicsCommandList::IASetVertexBuffers。

例如，

// Initialize the vertex buffer view.
m_vertexBufferView.BufferLocation = m_vertexBuffer->GetGPUVirtualAddress();
m_vertexBufferView.SizeInBytes = SampleAssets::VertexDataSize;
m_vertexBufferView.StrideInBytes = SampleAssets::StandardVertexStride;

着色器资源视图

要创建着色器资源视图，请填写 D3D12_SHADER_RESOURCE_VIEW_DESC 结构：

typedef struct D3D12_SHADER_RESOURCE_VIEW_DESC  
    {  
    DXGI_FORMAT Format;  
    D3D12_SRV_DIMENSION ViewDimension;  
    UINT Shader4ComponentMapping;  
    union   
        {  
        D3D12_BUFFER_SRV Buffer;  
        D3D12_TEX1D_SRV Texture1D;  
        D3D12_TEX1D_ARRAY_SRV Texture1DArray;  
        D3D12_TEX2D_SRV Texture2D;  
        D3D12_TEX2D_ARRAY_SRV Texture2DArray;  
        D3D12_TEX2DMS_SRV Texture2DMS;  
        D3D12_TEX2DMS_ARRAY_SRV Texture2DMSArray;  
        D3D12_TEX3D_SRV Texture3D;  
        D3D12_TEXCUBE_SRV TextureCube;  
        D3D12_TEXCUBE_ARRAY_SRV TextureCubeArray;  
        }   ;  
    }   D3D12_SHADER_RESOURCE_VIEW_DESC; 

ViewDimension 字段设置为 D3D12_SRV_DIMENSION 枚举的值。

D3D12_SHADER_RESOURCE_VIEW_DESC 引用的枚举和结构为：

• DXGI_FORMAT
• D3D12_BUFFER_SRV
• D3D12_TEX1D_SRV
• D3D12_TEX1D_ARRAY_SRV
• D3D12_TEX2D_SRV
• D3D12_TEX2D_ARRAY_SRV
• D3D12_TEX2DMS_SRV
• D3D12_TEX2DMS_ARRAY_SRV
• D3D12_TEX3D_SRV
• D3D12_TEXCUBE_SRV
• D3D12_TEXCUBE_ARRAY_SRV

注意

在下面的代码示例中，浮点数 ResourceMinLODClamp 是 Tex1D/2D/3D/Cube 的 SRV 的一部分。 在 Direct3D 11 中，它是一个资源属性，但这与它在硬件中的实现方式不匹配。 StructureByteStride 是缓冲区 SRV 的一部分；而在 Direct3D 11 中，它是一个资源属性。 如果步幅为非零值，这表示结构化的缓冲区视图，则格式必须设置为 DXGI_FORMAT_UNKNOWN。

最后，若要创建着色器资源视图，请调用 ID3D12Device::CreateShaderResourceView。

例如，

// Describe and create an SRV.
D3D12_SHADER_RESOURCE_VIEW_DESC srvDesc = {};
srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
srvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
srvDesc.Format = tex.Format;
srvDesc.Texture2D.MipLevels = tex.MipLevels;
srvDesc.Texture2D.MostDetailedMip = 0;
srvDesc.Texture2D.ResourceMinLODClamp = 0.0f;
m_device->CreateShaderResourceView(m_textures[i].Get(), &srvDesc, cbvSrvHandle);

常量缓冲区视图

要创建常量缓冲区视图，请填写 D3D12_CONSTANT_BUFFER_VIEW_DESC 结构：

typedef struct D3D12_CONSTANT_BUFFER_VIEW_DESC {
  D3D12_GPU_VIRTUAL_ADDRESS BufferLocation;
  UINT   SizeInBytes;
} D3D12_CONSTANT_BUFFER_VIEW_DESC;

然后调用 ID3D12Device::CreateConstantBufferView。

例如，

// Describe and create a constant buffer view.
D3D12_CONSTANT_BUFFER_VIEW_DESC cbvDesc = {};
cbvDesc.BufferLocation = m_constantBuffer->GetGPUVirtualAddress();
cbvDesc.SizeInBytes = (sizeof(ConstantBuffer) + 255) & ~255;    // CB size is required to be 256-byte aligned.
m_device->CreateConstantBufferView(&cbvDesc, m_cbvHeap->GetCPUDescriptorHandleForHeapStart());

取样器

要创建取样器，请填写 D3D12_SAMPLER_DESC 结构：

typedef struct D3D12_SAMPLER_DESC
{
    D3D12_FILTER Filter;
    D3D12_TEXTURE_ADDRESS_MODE AddressU;
    D3D12_TEXTURE_ADDRESS_MODE AddressV;
    D3D12_TEXTURE_ADDRESS_MODE AddressW;
    FLOAT MipLODBias;
    UINT MaxAnisotropy;
    D3D12_COMPARISON_FUNC ComparisonFunc;
    FLOAT BorderColor[4]; // RGBA
    FLOAT MinLOD;
    FLOAT MaxLOD;
} D3D12_SAMPLER_DESC;

若要填写此结构，参阅以下枚举：

• D3D12_FILTER
• D3D12_FILTER_TYPE
• D3D12_FILTER_REDUCTION_TYPE
• D3D12_TEXTURE_ADDRESS_MODE
• D3D12_COMPARISON_FUNC

最后，调用 ID3D12Device::CreateSampler。

例如，

// Describe and create a sampler.
D3D12_SAMPLER_DESC samplerDesc = {};
samplerDesc.Filter = D3D12_FILTER_MIN_MAG_MIP_LINEAR;
samplerDesc.AddressU = D3D12_TEXTURE_ADDRESS_MODE_WRAP;
samplerDesc.AddressV = D3D12_TEXTURE_ADDRESS_MODE_WRAP;
samplerDesc.AddressW = D3D12_TEXTURE_ADDRESS_MODE_WRAP;
samplerDesc.MinLOD = 0;
samplerDesc.MaxLOD = D3D12_FLOAT32_MAX;
samplerDesc.MipLODBias = 0.0f;
samplerDesc.MaxAnisotropy = 1;
samplerDesc.ComparisonFunc = D3D12_COMPARISON_FUNC_ALWAYS;
m_device->CreateSampler(&samplerDesc, m_samplerHeap->GetCPUDescriptorHandleForHeapStart());

无序访问视图

要创建无序访问视图，请填写 D3D12_UNORDERED_ACCESS_VIEW_DESC 结构：

typedef struct D3D12_UNORDERED_ACCESS_VIEW_DESC
{
    DXGI_FORMAT Format;
    D3D12_UAV_DIMENSION ViewDimension;

    union
    {
        D3D12_BUFFER_UAV Buffer;
        D3D12_TEX1D_UAV Texture1D;
        D3D12_TEX1D_ARRAY_UAV Texture1DArray;
        D3D12_TEX2D_UAV Texture2D;
        D3D12_TEX2D_ARRAY_UAV Texture2DArray;
        D3D12_TEX3D_UAV Texture3D;
    };
} D3D12_UNORDERED_ACCESS_VIEW_DESC;

ViewDimension 字段设置为零，或者设置为 D3D12_BUFFER_UAV_FLAGS 枚举的一个值。

请参阅以下枚举和结构：

• DXGI_FORMAT
• D3D12_BUFFER_UAV
• D3D12_TEX1D_UAV
• D3D12_TEX1D_ARRAY_UAV
• D3D12_TEX2D_UAV
• D3D12_TEX2D_ARRAY_UAV
• D3D12_TEX3D_UAV

StructureByteStride 是缓冲区 UAV 的一部分；而在 Direct3D 11 中，它是一个资源属性。 如果步幅为非零值，这表示结构化的缓冲区视图，则格式必须设置为 DXGI_FORMAT_UNKNOWN。

最后调用 ID3D12Device::CreateUnorderedAccessView。

例如，

// Create the unordered access views (UAVs) that store the results of the compute work.
CD3DX12_CPU_DESCRIPTOR_HANDLE processedCommandsHandle(m_cbvSrvUavHeap->GetCPUDescriptorHandleForHeapStart(), ProcessedCommandsOffset, m_cbvSrvUavDescriptorSize);
for (UINT frame = 0; frame < FrameCount; frame++)
{
    // Allocate a buffer large enough to hold all of the indirect commands
    // for a single frame as well as a UAV counter.
    commandBufferDesc = CD3DX12_RESOURCE_DESC::Buffer(CommandBufferSizePerFrame + sizeof(UINT), D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS);
    ThrowIfFailed(m_device->CreateCommittedResource(
        &CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT),
        D3D12_HEAP_FLAG_NONE,
        &commandBufferDesc,
        D3D12_RESOURCE_STATE_COPY_DEST,
        nullptr,
        IID_PPV_ARGS(&m_processedCommandBuffers[frame])));

    D3D12_UNORDERED_ACCESS_VIEW_DESC uavDesc = {};
    uavDesc.Format = DXGI_FORMAT_UNKNOWN;
    uavDesc.ViewDimension = D3D12_UAV_DIMENSION_BUFFER;
    uavDesc.Buffer.FirstElement = 0;
    uavDesc.Buffer.NumElements = TriangleCount;
    uavDesc.Buffer.StructureByteStride = sizeof(IndirectCommand);
    uavDesc.Buffer.CounterOffsetInBytes = CommandBufferSizePerFrame;
    uavDesc.Buffer.Flags = D3D12_BUFFER_UAV_FLAG_NONE;

    m_device->CreateUnorderedAccessView(            
        m_processedCommandBuffers[frame].Get(),
        m_processedCommandBuffers[frame].Get(),
        &uavDesc,
        processedCommandsHandle);

    processedCommandsHandle.Offset(CbvSrvUavDescriptorCountPerFrame, m_cbvSrvUavDescriptorSize);
}

// Allocate a buffer that can be used to reset the UAV counters and initialize it to 0.
ThrowIfFailed(m_device->CreateCommittedResource(
    &CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_UPLOAD),
    D3D12_HEAP_FLAG_NONE,
    &CD3DX12_RESOURCE_DESC::Buffer(sizeof(UINT)),
    D3D12_RESOURCE_STATE_GENERIC_READ,
    
    nullptr,
    IID_PPV_ARGS(&m_processedCommandBufferCounterReset)));

UINT8* pMappedCounterReset = nullptr;
CD3DX12_RANGE readRange(0, 0);        // We do not intend to read from this resource on the CPU.
ThrowIfFailed(m_processedCommandBufferCounterReset->Map(0, &readRange, reinterpret_cast<void**>(&pMappedCounterReset)));
ZeroMemory(pMappedCounterReset, sizeof(UINT));
m_processedCommandBufferCounterReset->Unmap(0, nullptr);

流输出视图

要创建流输出视图，请填写 D3D12_STREAM_OUTPUT_DESC 结构。

typedef struct D3D12_STREAM_OUTPUT_DESC  
    {  
    _Field_size_full_(NumEntries)  const D3D12_SO_DECLARATION_ENTRY *pSODeclaration;  
    UINT NumEntries;  
    _Field_size_full_(NumStrides)  const UINT *pBufferStrides;  
    UINT NumStrides;  
    UINT RasterizedStream;  
    }   D3D12_STREAM_OUTPUT_DESC;  

然后调用 ID3D12GraphicsCommandList::SOSetTargets。

呈现器目标视图

要创建呈现器目标视图，请填写 D3D12_RENDER_TARGET_VIEW_DESC 结构。

typedef struct D3D12_RENDER_TARGET_VIEW_DESC
{
    DXGI_FORMAT Format;
    D3D12_RTV_DIMENSION ViewDimension;

    union
    {
        D3D12_BUFFER_RTV Buffer;
        D3D12_TEX1D_RTV Texture1D;
        D3D12_TEX1D_ARRAY_RTV Texture1DArray;
        D3D12_TEX2D_RTV Texture2D;
        D3D12_TEX2D_ARRAY_RTV Texture2DArray;
        D3D12_TEX2DMS_RTV Texture2DMS;
        D3D12_TEX2DMS_ARRAY_RTV Texture2DMSArray;
        D3D12_TEX3D_RTV Texture3D;
    };
} D3D12_RENDER_TARGET_VIEW_DESC;

ViewDimension 字段设置为零，或者设置为 D3D12_RTV_DIMENSION 枚举的一个值。

请参阅以下枚举和结构：

• DXGI_FORMAT
• D3D12_BUFFER_RTV
• D3D12_TEX1D_RTV
• D3D12_TEX1D_ARRAY_RTV
• D3D12_TEX2D_RTV
• D3D12_TEX2DMS_RTV
• D3D12_TEX2D_ARRAY_RTV
• D3D12_TEX2DMS_ARRAY_RTV
• D3D12_TEX3D_RTV

最后，调用 ID3D12Device::CreateRenderTargetView。

例如，

// Create descriptor heaps.
{
    // Describe and create a render target view (RTV) descriptor heap.
    D3D12_DESCRIPTOR_HEAP_DESC rtvHeapDesc = {};
    rtvHeapDesc.NumDescriptors = FrameCount;
    rtvHeapDesc.Type = D3D12_DESCRIPTOR_HEAP_TYPE_RTV;
    rtvHeapDesc.Flags = D3D12_DESCRIPTOR_HEAP_FLAG_NONE;
    ThrowIfFailed(m_device->CreateDescriptorHeap(&rtvHeapDesc, IID_PPV_ARGS(&m_rtvHeap)));

    m_rtvDescriptorSize = m_device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_RTV);
}

// Create frame resources.
{
    CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(m_rtvHeap->GetCPUDescriptorHandleForHeapStart());

    // Create a RTV for each frame.
    for (UINT n = 0; n < FrameCount; n++)
    {
        ThrowIfFailed(m_swapChain->GetBuffer(n, IID_PPV_ARGS(&m_renderTargets[n])));
        m_device->CreateRenderTargetView(m_renderTargets[n].Get(), nullptr, rtvHandle);
        rtvHandle.Offset(1, m_rtvDescriptorSize);
    }

深度模具视图

要创建深度模具视图，请填写 D3D12_DEPTH_STENCIL_VIEW_DESC 结构：

typedef struct D3D12_DEPTH_STENCIL_VIEW_DESC  
    {  
    DXGI_FORMAT Format;  
    D3D12_DSV_DIMENSION ViewDimension;  
    D3D12_DSV_FLAGS Flags;  
    union   
        {  
        D3D12_TEX1D_DSV Texture1D;  
        D3D12_TEX1D_ARRAY_DSV Texture1DArray;  
        D3D12_TEX2D_DSV Texture2D;  
        D3D12_TEX2D_ARRAY_DSV Texture2DArray;  
        D3D12_TEX2DMS_DSV Texture2DMS;  
        D3D12_TEX2DMS_ARRAY_DSV Texture2DMSArray;  
        }   ;  
    }   D3D12_DEPTH_STENCIL_VIEW_DESC;  

ViewDimension 字段设置为零，或者设置为 D3D12_DSV_DIMENSION 枚举的一个值。 有关标志设置，请参阅 D3D12_DSV_FLAGS 枚举。

请参阅以下枚举和结构：

• DXGI_FORMAT
• D3D12_TEX1D_DSV
• D3D12_TEX1D_ARRAY_DSV
• D3D12_TEX2D_DSV
• D3D12_TEX2D_ARRAY_DSV
• D3D12_TEX2DMS_DSV
• D3D12_TEX2DMS_ARRAY_DSV

最后，调用 ID3D12Device::CreateDepthStencilView。

例如，

// Create the depth stencil view.
{
    D3D12_DEPTH_STENCIL_VIEW_DESC depthStencilDesc = {};
    depthStencilDesc.Format = DXGI_FORMAT_D32_FLOAT;
    depthStencilDesc.ViewDimension = D3D12_DSV_DIMENSION_TEXTURE2D;
    depthStencilDesc.Flags = D3D12_DSV_FLAG_NONE;

    D3D12_CLEAR_VALUE depthOptimizedClearValue = {};
    depthOptimizedClearValue.Format = DXGI_FORMAT_D32_FLOAT;
    depthOptimizedClearValue.DepthStencil.Depth = 1.0f;
    depthOptimizedClearValue.DepthStencil.Stencil = 0;

    ThrowIfFailed(m_device->CreateCommittedResource(
        &CD3DX12_HEAP_PROPERTIES(D3D12_HEAP_TYPE_DEFAULT),
        D3D12_HEAP_FLAG_NONE,
        &CD3DX12_RESOURCE_DESC::Tex2D(DXGI_FORMAT_D32_FLOAT, m_width, m_height, 1, 0, 1, 0, D3D12_RESOURCE_FLAG_ALLOW_DEPTH_STENCIL),
        D3D12_RESOURCE_STATE_DEPTH_WRITE,
        &depthOptimizedClearValue,
        IID_PPV_ARGS(&m_depthStencil)
        ));

    m_device->CreateDepthStencilView(m_depthStencil.Get(), &depthStencilDesc, m_dsvHeap->GetCPUDescriptorHandleForHeapStart());
}

相关主题

• 描述符
• 描述符堆