ID3D12Fence::GetCompletedValue method

UINT64 GetCompletedValue();

void D3D12HelloTriangle::WaitForPreviousFrame()
{
    // WAITING FOR THE FRAME TO COMPLETE BEFORE CONTINUING IS NOT BEST PRACTICE.
    // This is code implemented as such for simplicity. More advanced samples 
    // illustrate how to use fences for efficient resource usage.

    // Signal and increment the fence value.
    const UINT64 fence = m_fenceValue;
    ThrowIfFailed(m_commandQueue->Signal(m_fence.Get(), fence));
    m_fenceValue++;

    // Wait until the previous frame is finished.
    if (m_fence->GetCompletedValue() < fence)
    {
        ThrowIfFailed(m_fence->SetEventOnCompletion(fence, m_fenceEvent));
        WaitForSingleObject(m_fenceEvent, INFINITE);
    }

    m_frameIndex = m_swapChain->GetCurrentBackBufferIndex();
}

DWORD D3D12nBodyGravity::AsyncComputeThreadProc(int threadIndex)
{
    ID3D12CommandQueue* pCommandQueue = m_computeCommandQueue[threadIndex].Get();
    ID3D12CommandAllocator* pCommandAllocator = m_computeAllocator[threadIndex].Get();
    ID3D12GraphicsCommandList* pCommandList = m_computeCommandList[threadIndex].Get();
    ID3D12Fence* pFence = m_threadFences[threadIndex].Get();

    while (0 == InterlockedGetValue(&m_terminating))
    {
        // Run the particle simulation.
        Simulate(threadIndex);

        // Close and execute the command list.
        ThrowIfFailed(pCommandList->Close());
        ID3D12CommandList* ppCommandLists[] = { pCommandList };

        pCommandQueue->ExecuteCommandLists(1, ppCommandLists);

        // Wait for the compute shader to complete the simulation.
        UINT64 threadFenceValue = InterlockedIncrement(&m_threadFenceValues[threadIndex]);
        ThrowIfFailed(pCommandQueue->Signal(pFence, threadFenceValue));
        ThrowIfFailed(pFence->SetEventOnCompletion(threadFenceValue, m_threadFenceEvents[threadIndex]));
        WaitForSingleObject(m_threadFenceEvents[threadIndex], INFINITE);

        // Wait for the render thread to be done with the SRV so that
        // the next frame in the simulation can run.
        UINT64 renderContextFenceValue = InterlockedGetValue(&m_renderContextFenceValues[threadIndex]);
        if (m_renderContextFence->GetCompletedValue() < renderContextFenceValue)
        {
            ThrowIfFailed(pCommandQueue->Wait(m_renderContextFence.Get(), renderContextFenceValue));
            InterlockedExchange(&m_renderContextFenceValues[threadIndex], 0);
        }

        // Swap the indices to the SRV and UAV.
        m_srvIndex[threadIndex] = 1 - m_srvIndex[threadIndex];

        // Prepare for the next frame.
        ThrowIfFailed(pCommandAllocator->Reset());
        ThrowIfFailed(pCommandList->Reset(pCommandAllocator, m_computeState.Get()));
    }

    return 0;
}