使用 HLSL 5.1 的動態索引編制
D3D12DynamicIndexing範例示範著色器模型 5.1 中提供的一些新的 HLSL 功能，特別是動態索引和未系結的陣列，每次使用動態選取的材質來轉譯相同的網格。 使用動態索引編制時，著色器現在可以編制陣列的索引，而不需要在編譯時期知道索引的值。 結合未系結的陣列時，這會為著色器作者和藝術管線新增另一層間接和彈性。
設定圖元著色器
讓我們先看看著色器本身，此範例是圖元著色器。
Texture2D g_txDiffuse : register(t0);
Texture2D g_txMats[] : register(t1);
SamplerState g_sampler : register(s0);
struct PSSceneIn
{
float4 pos : SV_Position;
float2 tex : TEXCOORD0;
};
struct MaterialConstants
{
uint matIndex; // Dynamically set index for looking up from g_txMats[].
};
ConstantBuffer<MaterialConstants> materialConstants : register(b0, space0);
float4 PSSceneMain(PSSceneIn input) : SV_Target
{
float3 diffuse = g_txDiffuse.Sample(g_sampler, input.tex).rgb;
float3 mat = g_txMats[materialConstants.matIndex].Sample(g_sampler, input.tex).rgb;
return float4(diffuse * mat, 1.0f);
}
未系結的陣列功能是由陣列說明， g_txMats[] 因為它未指定陣列大小。 動態索引是用來使用 matIndex 來編制索引 g_txMats[] ，其定義為根常數。 著色器在編譯時期不知道大小或陣列或索引的值。 這兩個屬性都是定義在與著色器搭配使用的管線狀態物件的根簽章中。
若要利用 HLSL 中的動態索引功能，您必須使用 SM 5.1 編譯著色器。 此外，若要使用未系結的陣列，也必須使用 /enable_unbounded_descriptor_tables 旗標。 下列命令列選項可用來使用 Effect-Compiler Tool (FXC) 來編譯此著色器：
fxc /Zi /E"PSSceneMain" /Od /Fo"dynamic_indexing_pixel.cso" /ps"_5_1" /nologo /enable_unbounded_descriptor_tables
設定根簽章
現在，讓我們看看根簽章定義，特別是如何定義未系結陣列的大小，並將根常數連結至 matIndex 。 針對圖元著色器，我們會定義三件事：SRV 的描述中繼資料表， (Texture2Ds) 、取樣器的描述中繼資料表和單一根常數。 SRV 的描述項資料表包含 CityMaterialCount + 1 專案。
CityMaterialCount 是定義 長度的 g_txMats[] 常數，而 + 1 則為 g_txDiffuse 。 Samplers 的描述中繼資料表只包含一個專案，而且我們在LoadAssets方法中，只會透過InitAsConstants (...) 定義一個 32 位根常數值。
// Create the root signature.
{
CD3DX12_DESCRIPTOR_RANGE ranges[3];
ranges[0].Init(D3D12_DESCRIPTOR_RANGE_TYPE_SRV, 1 + CityMaterialCount, 0); // Diffuse texture + array of materials.
ranges[1].Init(D3D12_DESCRIPTOR_RANGE_TYPE_SAMPLER, 1, 0);
ranges[2].Init(D3D12_DESCRIPTOR_RANGE_TYPE_CBV, 1, 0);
CD3DX12_ROOT_PARAMETER rootParameters[4];
rootParameters[0].InitAsDescriptorTable(1, &ranges[0], D3D12_SHADER_VISIBILITY_PIXEL);
rootParameters[1].InitAsDescriptorTable(1, &ranges[1], D3D12_SHADER_VISIBILITY_PIXEL);
rootParameters[2].InitAsDescriptorTable(1, &ranges[2], D3D12_SHADER_VISIBILITY_VERTEX);
rootParameters[3].InitAsConstants(1, 0, 0, D3D12_SHADER_VISIBILITY_PIXEL);
CD3DX12_ROOT_SIGNATURE_DESC rootSignatureDesc;
rootSignatureDesc.Init(_countof(rootParameters), rootParameters, 0, nullptr, D3D12_ROOT_SIGNATURE_FLAG_ALLOW_INPUT_ASSEMBLER_INPUT_LAYOUT);
ComPtr<ID3DBlob> signature;
ComPtr<ID3DBlob> error;
ThrowIfFailed(D3D12SerializeRootSignature(&rootSignatureDesc, D3D_ROOT_SIGNATURE_VERSION_1, &signature, &error));
ThrowIfFailed(m_device->CreateRootSignature(0, signature->GetBufferPointer(), signature->GetBufferSize(), IID_PPV_ARGS(&m_rootSignature)));
}
建立紋理
的內容 g_txMats[] 是在 LoadAssets中建立的程式性產生的紋理。 在場景中呈現的每個城市都會共用相同的擴散紋理，但每個城市也有自己的程式性產生的紋理。 紋理的陣列橫跨各式各樣的範圍，以輕鬆地將索引編制技術視覺化。
// Create the textures and sampler.
{
// Procedurally generate an array of textures to use as city materials.
{
// All of these materials use the same texture desc.
D3D12_RESOURCE_DESC textureDesc = {};
textureDesc.MipLevels = 1;
textureDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
textureDesc.Width = CityMaterialTextureWidth;
textureDesc.Height = CityMaterialTextureHeight;
textureDesc.Flags = D3D12_RESOURCE_FLAG_NONE;
textureDesc.DepthOrArraySize = 1;
textureDesc.SampleDesc.Count = 1;
textureDesc.SampleDesc.Quality = 0;
textureDesc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
// The textures evenly span the color rainbow so that each city gets
// a different material.
float materialGradStep = (1.0f / static_cast<float>(CityMaterialCount));
// Generate texture data.
vector<vector<unsigned char>> cityTextureData;
cityTextureData.resize(CityMaterialCount);
for (int i = 0; i < CityMaterialCount; ++i)
{
CD3DX12_HEAP_PROPERTIES heapProps(D3D12_HEAP_TYPE_DEFAULT);
ThrowIfFailed(m_device->CreateCommittedResource(
&heapProps,
D3D12_HEAP_FLAG_NONE,
&textureDesc,
D3D12_RESOURCE_STATE_COPY_DEST,
nullptr,
IID_PPV_ARGS(&m_cityMaterialTextures[i])));
// Fill the texture.
float t = i * materialGradStep;
cityTextureData[i].resize(CityMaterialTextureWidth * CityMaterialTextureHeight * CityMaterialTextureChannelCount);
for (int x = 0; x < CityMaterialTextureWidth; ++x)
{
for (int y = 0; y < CityMaterialTextureHeight; ++y)
{
// Compute the appropriate index into the buffer based on the x/y coordinates.
int pixelIndex = (y * CityMaterialTextureChannelCount * CityMaterialTextureWidth) + (x * CityMaterialTextureChannelCount);
// Determine this row's position along the rainbow gradient.
float tPrime = t + ((static_cast<float>(y) / static_cast<float>(CityMaterialTextureHeight)) * materialGradStep);
// Compute the RGB value for this position along the rainbow
// and pack the pixel value.
XMVECTOR hsl = XMVectorSet(tPrime, 0.5f, 0.5f, 1.0f);
XMVECTOR rgb = XMColorHSLToRGB(hsl);
cityTextureData[i][pixelIndex + 0] = static_cast<unsigned char>((255 * XMVectorGetX(rgb)));
cityTextureData[i][pixelIndex + 1] = static_cast<unsigned char>((255 * XMVectorGetY(rgb)));
cityTextureData[i][pixelIndex + 2] = static_cast<unsigned char>((255 * XMVectorGetZ(rgb)));
cityTextureData[i][pixelIndex + 3] = 255;
}
}
}
}
| 通話流程 | 參數 |
|---|---|
| D3D12_RESOURCE_DESC |
D3D12_RESOURCE_FLAGS [D3D12_RESOURCE_DIMENSION] (/windows/desktop/api/d3d12/ne-d3d12-d3d12_resource_dimension) |
| CreateCommittedResource |
D3D12_HEAP_TYPE [D3D12_HEAP_FLAG] ( /windows/desktop/api/d3d12/ne-d3d12-d3d12_heap_flags) CD3DX12_RESOURCE_DESC [D3D12_RESOURCE_STATES] (/windows/desktop/api/d3d12/ne-d3d12-d3d12_resource_states) |
| XMVECTOR |
[XMColorHSLToRGB] (/windows/desktop/api/directxmath/nf-directxmath-xmcolorhsltorgb) |
上傳紋理資料
紋理資料會透過上傳堆積上傳至 GPU，並針對每個建立 SRV，並儲存在 SRV 描述元堆積中。
// Upload texture data to the default heap resources.
{
const UINT subresourceCount = textureDesc.DepthOrArraySize * textureDesc.MipLevels;
const UINT64 uploadBufferStep = GetRequiredIntermediateSize(m_cityMaterialTextures[0].Get(), 0, subresourceCount); // All of our textures are the same size in this case.
const UINT64 uploadBufferSize = uploadBufferStep * CityMaterialCount;
CD3DX12_HEAP_PROPERTIES uploadHeap(D3D12_HEAP_TYPE_UPLOAD);
auto uploadDesc = CD3DX12_RESOURCE_DESC::Buffer(uploadBufferSize);
ThrowIfFailed(m_device->CreateCommittedResource(
&uploadHeap,
D3D12_HEAP_FLAG_NONE,
&uploadDesc,
D3D12_RESOURCE_STATE_GENERIC_READ,
nullptr,
IID_PPV_ARGS(&materialsUploadHeap)));
for (int i = 0; i < CityMaterialCount; ++i)
{
// Copy data to the intermediate upload heap and then schedule
// a copy from the upload heap to the appropriate texture.
D3D12_SUBRESOURCE_DATA textureData = {};
textureData.pData = &cityTextureData[i][0];
textureData.RowPitch = static_cast<LONG_PTR>((CityMaterialTextureChannelCount * textureDesc.Width));
textureData.SlicePitch = textureData.RowPitch * textureDesc.Height;
UpdateSubresources(m_commandList.Get(), m_cityMaterialTextures[i].Get(), materialsUploadHeap.Get(), i * uploadBufferStep, 0, subresourceCount, &textureData);
auto barrier = CD3DX12_RESOURCE_BARRIER::Transition(m_cityMaterialTextures[i].Get(), D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE);
m_commandList->ResourceBarrier(1, &barrier);
}
}
| 通話流程 | 參數 |
|---|---|
| GetRequiredIntermediateSize | |
| CreateCommittedResource | |
| D3D12_SUBRESOURCE_DATA | |
| UpdateSubresources | |
| ResourceBarrier |
載入擴散紋理
擴散紋理g_ txDiffuse 會以類似的方式上傳，同時也會取得自己的 SRV，但紋理資料已在 occcity.bin 中定義。
// Load the occcity diffuse texture with baked-in ambient lighting.
// This texture will be blended with a texture from the materials
// array in the pixel shader.
{
D3D12_RESOURCE_DESC textureDesc = {};
textureDesc.MipLevels = SampleAssets::Textures[0].MipLevels;
textureDesc.Format = SampleAssets::Textures[0].Format;
textureDesc.Width = SampleAssets::Textures[0].Width;
textureDesc.Height = SampleAssets::Textures[0].Height;
textureDesc.Flags = D3D12_RESOURCE_FLAG_NONE;
textureDesc.DepthOrArraySize = 1;
textureDesc.SampleDesc.Count = 1;
textureDesc.SampleDesc.Quality = 0;
textureDesc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
CD3DX12_HEAP_PROPERTIES heapProps(D3D12_HEAP_TYPE_DEFAULT);
ThrowIfFailed(m_device->CreateCommittedResource(
&heapProps,
D3D12_HEAP_FLAG_NONE,
&textureDesc,
D3D12_RESOURCE_STATE_COPY_DEST,
nullptr,
IID_PPV_ARGS(&m_cityDiffuseTexture)));
const UINT subresourceCount = textureDesc.DepthOrArraySize * textureDesc.MipLevels;
const UINT64 uploadBufferSize = GetRequiredIntermediateSize(m_cityDiffuseTexture.Get(), 0, subresourceCount);
CD3DX12_HEAP_PROPERTIES uploadHeap(D3D12_HEAP_TYPE_UPLOAD);
auto uploadDesc = CD3DX12_RESOURCE_DESC::Buffer(uploadBufferSize);
ThrowIfFailed(m_device->CreateCommittedResource(
&uploadHeap,
D3D12_HEAP_FLAG_NONE,
&uploadDesc,
D3D12_RESOURCE_STATE_GENERIC_READ,
nullptr,
IID_PPV_ARGS(&textureUploadHeap)));
// Copy data to the intermediate upload heap and then schedule
// a copy from the upload heap to the diffuse texture.
D3D12_SUBRESOURCE_DATA textureData = {};
textureData.pData = pMeshData + SampleAssets::Textures[0].Data[0].Offset;
textureData.RowPitch = SampleAssets::Textures[0].Data[0].Pitch;
textureData.SlicePitch = SampleAssets::Textures[0].Data[0].Size;
UpdateSubresources(m_commandList.Get(), m_cityDiffuseTexture.Get(), textureUploadHeap.Get(), 0, 0, subresourceCount, &textureData);
auto barrier = CD3DX12_RESOURCE_BARRIER::Transition(m_cityDiffuseTexture.Get(), D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE);
m_commandList->ResourceBarrier(1, &barrier);
}
| 通話流程 | 參數 |
|---|---|
| D3D12_RESOURCE_DESC | |
| CreateCommittedResource | |
| GetRequiredIntermediateSize | |
| CreateCommittedResource | |
| D3D12_SUBRESOURCE_DATA | |
| ResourceBarrier |
建立取樣器
最後， 針對 LoadAssets，會建立單一取樣器，以從擴散紋理或紋理陣列取樣。
// 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());
// Create SRV for the city's diffuse texture.
CD3DX12_CPU_DESCRIPTOR_HANDLE srvHandle(m_cbvSrvHeap->GetCPUDescriptorHandleForHeapStart(), 0, m_cbvSrvDescriptorSize);
D3D12_SHADER_RESOURCE_VIEW_DESC diffuseSrvDesc = {};
diffuseSrvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
diffuseSrvDesc.Format = SampleAssets::Textures->Format;
diffuseSrvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
diffuseSrvDesc.Texture2D.MipLevels = 1;
m_device->CreateShaderResourceView(m_cityDiffuseTexture.Get(), &diffuseSrvDesc, srvHandle);
srvHandle.Offset(m_cbvSrvDescriptorSize);
// Create SRVs for each city material.
for (int i = 0; i < CityMaterialCount; ++i)
{
D3D12_SHADER_RESOURCE_VIEW_DESC materialSrvDesc = {};
materialSrvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
materialSrvDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
materialSrvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
materialSrvDesc.Texture2D.MipLevels = 1;
m_device->CreateShaderResourceView(m_cityMaterialTextures[i].Get(), &materialSrvDesc, srvHandle);
srvHandle.Offset(m_cbvSrvDescriptorSize);
}
動態變更根參數索引
如果我們現在要轉譯場景，則所有城市都會顯示相同，因為我們尚未設定根常數的值 。 matIndex 每個圖元著色器都會編制索引到 的第 0 個位置 g_txMats ，而場景看起來會像這樣：
根常數的值是在 FrameResource：:P opulateCommandLists中設定。 在針對每個城市記錄繪製命令的 double for 迴圈中，我們會記錄 對 SetGraphicsRoot32BitConstants 的呼叫，以指定根簽章的根參數索引 –在此案例中為 3 – 動態索引的值和位移 – 在此案例中為 0。 由於 的 g_txMats 長度等於我們轉譯的城市數目，因此會針對每個城市累加設定索引的值。
for (UINT i = 0; i < m_cityRowCount; i++)
{
for (UINT j = 0; j < m_cityColumnCount; j++)
{
pCommandList->SetPipelineState(pPso);
// Set the city's root constant for dynamically indexing into the material array.
pCommandList->SetGraphicsRoot32BitConstant(3, (i * m_cityColumnCount) + j, 0);
// Set this city's CBV table and move to the next descriptor.
pCommandList->SetGraphicsRootDescriptorTable(2, cbvSrvHandle);
cbvSrvHandle.Offset(cbvSrvDescriptorSize);
pCommandList->DrawIndexedInstanced(numIndices, 1, 0, 0, 0);
}
}
| 通話流程 | 參數 |
|---|---|
| SetPipelineState | |
| SetGraphicsRoot32BitConstant | |
| SetGraphicsRootDescriptorTable | |
| DrawIndexedInstanced |
執行範例
現在，當我們轉譯場景時，每個城市都會有不同的值 matIndex ，因此會查閱不同的紋理 g_txMats[] ，讓場景看起來像這樣：
