XBOX One 上的畫面排程與呈現

    // Game initialization.

    HRESULT hr;

    D3D12_HEAP_PROPERTIES heapProperties = {};
    heapProperties.Type = D3D12_HEAP_TYPE_DEFAULT;
    heapProperties.CPUPageProperty = D3D12_CPU_PAGE_PROPERTY_UNKNOWN;
    heapProperties.MemoryPoolPreference = D3D12_MEMORY_POOL_UNKNOWN;
    heapProperties.CreationNodeMask = D3D12XBOX_NODE_MASK;
    heapProperties.VisibleNodeMask = D3D12XBOX_NODE_MASK;

    D3D12_RESOURCE_DESC swapResourceDesc = {};
    swapResourceDesc.Dimension = D3D12_RESOURCE_DIMENSION_TEXTURE2D;
    swapResourceDesc.Alignment = 0;
    swapResourceDesc.Width = 1920;
    swapResourceDesc.Height = 1080;
    swapResourceDesc.DepthOrArraySize = 1;
    swapResourceDesc.Format = DXGI_FORMAT_R10G10B10A2_UNORM;
    swapResourceDesc.MipLevels = 1;
    swapResourceDesc.SampleDesc.Count = 1;
    swapResourceDesc.SampleDesc.Quality = 0;
    swapResourceDesc.Flags = D3D12_RESOURCE_FLAG_ALLOW_RENDER_TARGET | D3D12_RESOURCE_FLAG_ALLOW_UNORDERED_ACCESS;
    swapResourceDesc.Layout = D3D12_TEXTURE_LAYOUT_UNKNOWN;

    // Create a swap pool of two displayable resources.

    ID3D12Resource* pSwapResources[2];

    for (UINT i = 0; i < 2; ++i)
    {
        hr = pd3dDevice->CreateCommittedResource(
            &heapProperties,
            D3D12_HEAP_FLAG_ALLOW_DISPLAY,
            &swapResourceDesc,
            D3D12_RESOURCE_STATE_PRESENT,
            nullptr,
            __uuidof(ID3D12Resource),
            (void**)&pSwapResources[i]);

        if (FAILED(hr))
        {
            return hr;
        }
    }

    // Establish a 60 Hz frame-rate interval and a frame period spanning two intervals, which permits the
    // CPU to begin recording and submitting commands for one frame while the GPU is still processing
    // commands submitted on the previous frame (if the CPU attempts to begin work on frame n + 2 before
    // the GPU has completed frame n and flipped it to the display, it will be throttled until the interval
    // following the flip).

    hr = pd3dDevice->SetFrameIntervalX(
        nullptr,
        D3D12XBOX_FRAME_INTERVAL_60_HZ,         // 16,667 microseconds between flips (60 flips per second).
        2,                                      // Frame period of 2 intervals (frame started during one
                                                // interval and finished on the next).
        D3D12XBOX_FRAME_INTERVAL_FLAG_NONE);

    if (FAILED(hr))
    {
        return hr;
    }

    // Schedule a frame origin event to establish the CPU throttle point for the game. The frame
    // origin is the time that a new frame is generated, and is generally expected to be the
    // moment when input is queried and directly used in the construction of the frame. The
    // origin should be scheduled as near to the time of frame display as possible to minimize latency,
    // based on expected frame duration (and informed by statistics feedback). In this example,
    // the game anticipates an initial end-to-end frame duration (from input query, to CPU rendering,
    // to GPU processing, to presentation for display) of 27,778 microseconds (1.66 frame intervals).
    // This translates into a frame period of 2 intervals and an interval offset of 5,556 microseconds.

    hr = pd3dDevice->ScheduleFrameEventX(
        D3D12XBOX_FRAME_EVENT_ORIGIN,              // Origin event type.
        5556,                                      // Begin the frame after one-third of the interval has passed.
        nullptr,                                   // Don't signal any additional game events at the origin.
        D3D12XBOX_SCHEDULE_FRAME_EVENT_FLAG_NONE);

    if (FAILED(hr))
    {
        return hr;
    }

    {...}

    // Game loop.

    D3D12XBOX_FRAME_PIPELINE_TOKEN frameToken = D3D12XBOX_FRAME_PIPELINE_TOKEN_NULL;

    do
    {
        // Perform a modest, measured amount of CPU/GPU processing not directly dependent on user input
        // (for example, texture streaming).
        {...}

        // Poll on the origin event for the frame, throttling the CPU as necessary.

        hr = pd3dDevice->WaitFrameEventX(
            D3D12XBOX_FRAME_EVENT_ORIGIN,
            0,                                    // Poll with an immediate timeout.
            nullptr,                              // Don't wait on additional game events in
                                                  // conjunction with origin.
            D3D12XBOX_WAIT_FRAME_EVENT_FLAG_NONE,
            &token);                              // Obtain the frame's identifying token.

        if (hr == D3DERR_DEVICEREMOVED)
        {
            // The GPU may have stopped responding, preventing it from reaching the present submitted for
            // a previous frame and flipping it to the display. This would in turn prevent
            // the new frame origin event from being signaled due to the throttle. Alternatively,
            // another thread responsible for processing suspend events may have called
            // SuspendX during the origin wait, causing it to fail. Test and handle these
            // conditions as appropriate.
            {...}
        }

    } while (hr == S_FALSE);

    ++m_FrameIndex;

    // Store the frame token for later statistics retrieval.

    m_FrameToken[m_FrameIndex % 16] = token;

    // Query user input from the gamepad.

    IGameInputReading* pReading;

    pGameInput->GetCurrentReading(
        GameInputKindGamepad,
        pGamepadDevice,
        &pReading);

    // Render the frame based on the input reading to pSwapResources[m_FrameIndex % 2].

    {...}

    pReading->Release();

    // Queue the rendered frame for presentation to the display. Effective frame scheduling
    // will contrive to minimize the amount of time the swap resource remains in the queue
    // before being flipped and scanned out.

    D3D12XBOX_PRESENT_PLANE_PARAMETERS planeParameters = {};

    planeParameters.Token = token;                          // Identify the frame being presented.
    planeParameters.ResourceCount = 1;
    planeParameters.ppResources = &pSwapResources[m_FrameIndex % 2]; // Present the associated swap resource.
    planeParameters.pSrcViewRects = nullptr;                // Display the entire resource (no dynamic scaling
                                                            // or split-screen multiplayer).
    planeParameters.pDestPlacementBase = nullptr;           // Full coverage of the display.
    planeParameters.ColorSpace = DXGI_COLOR_SPACE_RGB_STUDIO_G22_NONE_P2020 // HDR color space.
    planeParameters.ScaleFilter = D3D12XBOX_PRESENT_PLANE_SCALE_FILTER_DEFAULT;
    planeParameters.Flags = D3D12XBOX_PRESENT_PLANE_FLAG_NONE;

    D3D12XBOX_PRESENT_PARAMETERS presentParameters = {};

    presentParameters.ImmediateThresholdPercent = 5.0f;     // Allow tearing in the top 5 percent of the frame.
    presentParameters.ViewCount = 1;                        // No split-screen multiplayer.
    presentParameters.Flags = D3D12XBOX_PRESENT_FLAG_NONE;

    pd3dCommandQueue->PresentX(
        1,
        &planeParameters,

    // Collect statistics for the most recently flipped frame.

    D3D12XBOX_FRAME_STATISTICS statisticsList[4];
    UINT statisticsCount = _countof(statisticsList);

    hr = pd3dDevice->GetFrameStatisticsX(
        m_FrameToken[(m_FrameIndex + 14) % 16],             // Query the frame originating 2 intervals in the past
                                                            // (display flip guaranteed).
        D3D12XBOX_FRAME_STATISTICS_TYPE_FRAME_EVENT |
            D3D12XBOX_FRAME_STATISTICS_TYPE_RENDER |
            D3D12XBOX_FRAME_STATISTICS_TYPE_PRESENT |
            D3D12XBOX_FRAME_STATISTICS_TYPE_DISPLAY,        // Query statistics relevant to latency analysis.
        &statisticsCount,                                   // Four entries is sufficient given no overlay and
        statisticsList);                                    // a single frame event type scheduled.

    if (SUCCEEDED(hr) &&
        (statisticsCount != 0))
    {
        bool originUpdate = false;
        UINT intervalOffsetInUs;

        // Analyze the returned statistics list to determine such things as frame length from origin to GPU
        // completion and display. Use the information to inform updates to frame scheduling with the goals
        // of minimizing latency while avoiding missed vblanks due to processing spikes.

        // Some possible considerations:
        //   Is D3D12XBOX_PRESENT_STATISTICS::GPUProcessTime too far from D3D12XBOX_DISPLAY_STATISTICS::VSyncTime?
        //     (Wasted latency from early frame completion.)
        //   Is D3D12XBOX_PRESENT_STATISTICS::GPUProcessTime too near to D3D12XBOX_DISPLAY_STATISTICS::VSyncTime?
        //     (Risk of frame drop from late frame completion.)
        //   Is D3D12XBOX_PRESENT_STATISTICS::GPUProcessTime not arriving soon after D3D12XBOX_RENDER_STATISTICS::
        //     GPUWriteCompleteTime? (Frame independent work done between swap resource completion and present
        //     instead of after present.)
        //   Is D3D12XBOX_FRAME_EVENT_STATISTICS::WaitCallTime too far from D3D12XBOX_FRAME_EVENT_STATISTICS::
        //     SignalTime? (Wait thread blocked on origin signal.)

        // When frame latency conditions have changed beyond some threshold margin, update the frame origin to
        // move it nearer to the target vblank (reduce latency) or further fom the vblank (avoid vblank miss).  
        // The frame origin update will be applied when the swap resource of the subsequent frame
        // (m_FrameIndex + 1) has been flipped to the display.

        if (originUpdate)
        {
            pd3dDevice->ScheduleFrameEventX(
                D3D12XBOX_FRAME_EVENT_ORIGIN,
                intervalOffsetInUs,
                nullptr,
                D3D12XBOX_SCHEDULE_FRAME_EVENT_FLAG_NONE);
        }
    }