ID3D12GraphicsCommandList::BeginQuery method (d3d12.h)

Article
02/22/2024

Starts a query running.

Syntax

void BeginQuery(
  [in] ID3D12QueryHeap  *pQueryHeap,
  [in] D3D12_QUERY_TYPE Type,
  [in] UINT             Index
);

Parameters

[in] pQueryHeap

Type: ID3D12QueryHeap*

Specifies the ID3D12QueryHeap containing the query.

[in] Type

Type: D3D12_QUERY_TYPE

Specifies one member of D3D12_QUERY_TYPE.

[in] Index

Type: UINT

Specifies the index of the query within the query heap.

Return value

None

Remarks

See Queries for more information about D3D12 queries.

Examples

The D3D12PredicationQueries sample uses ID3D12GraphicsCommandList::BeginQuery as follows:

// Fill the command list with all the render commands and dependent state.
void D3D12PredicationQueries::PopulateCommandList()
{
    // Command list allocators can only be reset when the associated 
    // command lists have finished execution on the GPU; apps should use 
    // fences to determine GPU execution progress.
    ThrowIfFailed(m_commandAllocators[m_frameIndex]->Reset());

    // However, when ExecuteCommandList() is called on a particular command 
    // list, that command list can then be reset at any time and must be before 
    // re-recording.
    ThrowIfFailed(m_commandList->Reset(m_commandAllocators[m_frameIndex].Get(), m_pipelineState.Get()));

    // Set necessary state.
    m_commandList->SetGraphicsRootSignature(m_rootSignature.Get());

    ID3D12DescriptorHeap* ppHeaps[] = { m_cbvHeap.Get() };
    m_commandList->SetDescriptorHeaps(_countof(ppHeaps), ppHeaps);

    m_commandList->RSSetViewports(1, &m_viewport);
    m_commandList->RSSetScissorRects(1, &m_scissorRect);

    // Indicate that the back buffer will be used as a render target.
    m_commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(m_renderTargets[m_frameIndex].Get(), D3D12_RESOURCE_STATE_PRESENT, D3D12_RESOURCE_STATE_RENDER_TARGET));

    CD3DX12_CPU_DESCRIPTOR_HANDLE rtvHandle(m_rtvHeap->GetCPUDescriptorHandleForHeapStart(), m_frameIndex, m_rtvDescriptorSize);
    CD3DX12_CPU_DESCRIPTOR_HANDLE dsvHandle(m_dsvHeap->GetCPUDescriptorHandleForHeapStart());
    m_commandList->OMSetRenderTargets(1, &rtvHandle, FALSE, &dsvHandle);

    // Record commands.
    const float clearColor[] = { 0.0f, 0.2f, 0.4f, 1.0f };
    m_commandList->ClearRenderTargetView(rtvHandle, clearColor, 0, nullptr);
    m_commandList->ClearDepthStencilView(dsvHandle, D3D12_CLEAR_FLAG_DEPTH, 1.0f, 0, 0, nullptr);

    // Draw the quads and perform the occlusion query.
    {
        CD3DX12_GPU_DESCRIPTOR_HANDLE cbvFarQuad(m_cbvHeap->GetGPUDescriptorHandleForHeapStart(), m_frameIndex * CbvCountPerFrame, m_cbvSrvDescriptorSize);
        CD3DX12_GPU_DESCRIPTOR_HANDLE cbvNearQuad(cbvFarQuad, m_cbvSrvDescriptorSize);

        m_commandList->IASetPrimitiveTopology(D3D_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP);
        m_commandList->IASetVertexBuffers(0, 1, &m_vertexBufferView);

        // Draw the far quad conditionally based on the result of the occlusion query
        // from the previous frame.
        m_commandList->SetGraphicsRootDescriptorTable(0, cbvFarQuad);
        m_commandList->SetPredication(m_queryResult.Get(), 0, D3D12_PREDICATION_OP_EQUAL_ZERO);
        m_commandList->DrawInstanced(4, 1, 0, 0);

        // Disable predication and always draw the near quad.
        m_commandList->SetPredication(nullptr, 0, D3D12_PREDICATION_OP_EQUAL_ZERO);
        m_commandList->SetGraphicsRootDescriptorTable(0, cbvNearQuad);
        m_commandList->DrawInstanced(4, 1, 4, 0);

        // Run the occlusion query with the bounding box quad.
        m_commandList->SetGraphicsRootDescriptorTable(0, cbvFarQuad);
        m_commandList->SetPipelineState(m_queryState.Get());
        m_commandList->BeginQuery(m_queryHeap.Get(), D3D12_QUERY_TYPE_BINARY_OCCLUSION, 0);
        m_commandList->DrawInstanced(4, 1, 8, 0);
        m_commandList->EndQuery(m_queryHeap.Get(), D3D12_QUERY_TYPE_BINARY_OCCLUSION, 0);

        // Resolve the occlusion query and store the results in the query result buffer
        // to be used on the subsequent frame.
        m_commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(m_queryResult.Get(), D3D12_RESOURCE_STATE_PREDICATION, D3D12_RESOURCE_STATE_COPY_DEST));
        m_commandList->ResolveQueryData(m_queryHeap.Get(), D3D12_QUERY_TYPE_BINARY_OCCLUSION, 0, 1, m_queryResult.Get(), 0);
        m_commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(m_queryResult.Get(), D3D12_RESOURCE_STATE_COPY_DEST, D3D12_RESOURCE_STATE_PREDICATION));
    }

    // Indicate that the back buffer will now be used to present.
    m_commandList->ResourceBarrier(1, &CD3DX12_RESOURCE_BARRIER::Transition(m_renderTargets[m_frameIndex].Get(), D3D12_RESOURCE_STATE_RENDER_TARGET, D3D12_RESOURCE_STATE_PRESENT));

    ThrowIfFailed(m_commandList->Close());
}

See Example Code in the D3D12 Reference.

Requirements

Requirement	Value
Target Platform	Windows
Header	d3d12.h
Library	D3d12.lib
DLL	D3d12.dll

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