c++ - Direct3D 11 缺少 GetRasterStatus，如何检测垂直空白期？

Question

我正在更新一个应用程序，在该应用程序中，屏幕上刺激呈现时间的测量需要最大的准确性。目前是用DirectDraw写的，很久以前就放牧了，需要更新我们的图形库。

我们测量显示时间的方法是利用检测垂直空白期的结束。具体来说，我需要尽可能准确地知道翻转到主表面(或出现在交换链中)的任何内容何时真正被屏幕绘制。检测扫描线可以增加该测量的确定性，但我只能检测调用 Flip 或 Present 后垂直空白期何时结束。

Direct 3D 9 具有 IDirect3DDevice9::GetRasterStatus Method返回一个 D3DRASTER_STATUS 结构，其中包含一个 InVBlank bool 值，描述设备是否处于垂直空白以及当前扫描线。 DirectDraw 具有类似的功能( IDirectDraw::GetVerticalBlankStatus ，在垂直空白期间返回 DDERR_VERTICALBLANKINPROGRESS 的 IDirectDraw::GetScanLine 也可用于检测 VB)。

但是我没能在 Direct3D11 中找到任何类似的函数。有谁知道此功能是否在 Direct3D9 和 Direct3D11 之间移动或删除，如果是后者，为什么？

Answer 1

很抱歉回复晚了，但我注意到仍然没有公认的答案，所以也许您从未找到有效的答案。如今在 Windows 上，DesktopWindowManager 服务 (dwm.exe) 协调一切，无法真正绕过。自 Windows 8 以来，此服务无法禁用。

因此 DWM 总是会控制帧速率、渲染队列管理以及所有各种 IDXGISurface(n) 对象和 IDXGIOutput(n) 监视器的最终合成，并且在跟踪 VSync 方面没有太大用处屏幕外渲染目标，除非我遗漏了什么(无意讽刺)。至于您的问题，我不确定您的目标是否是:

1. 获取极其精确的时间信息，但仅用于诊断、分析或信息用途，或者
2. 应用程序是否会(尝试)使用这些结果来(尝试)安排自己的当前周期。

如果是后者，我相信只有当 D3D 应用程序在全屏独占 模式下运行时，您才能有效地执行此操作。只有这样，DWM(以 DXGI 为幌子)才会真正信任客户端来处理它自己的Present 计时。

这里的(勉强)好消息是，如果您对 VSync 的兴趣仅供引用——也就是说您属于上面的项目符号类别 (1.)——那么您确实可以获得您想要的所有时序数据，以及 QueryPerformanceFrequency 分辨率，通常在 320 ns.¹ 左右

以下是获取高分辨率视频时间信息的方法。但是，再次明确一点，尽管在获取信息方面取得了明显的成功，如下所示，但任何使用这些有趣结果的尝试，例如，将某些确定性的——因此可能有用的——结果作为你获得的读数的条件将注定要失败，也就是说，完全被 DWM 中介所挫败:

DWM_TIMING_INFO

Specifies Desktop Window Manager (DWM) composition timing information. Used by the DwmGetCompositionTimingInfo function.

typedef struct _DWM_TIMING_INFO
{
    UINT32    cbSize;                 // size of this DWM_TIMING_INFO structure
    URATIO    rateRefresh;            // monitor refresh rate
    QPC_TIME  qpcRefreshPeriod;       // monitor refresh period
    URATIO    rateCompose;            // composition rate
    QPC_TIME  qpcVBlank;              // query performance counter value before the vertical blank
    CFRAMES   cRefresh;               // DWM refresh counter
    UINT      cDXRefresh;             // DirectX refresh counter
    QPC_TIME  qpcCompose;             // query performance counter value for a frame composition
    CFRAMES   cFrame;                 // frame number that was composed at qpcCompose
    UINT      cDXPresent;             // DirectX present number used to identify rendering frames
    CFRAMES   cRefreshFrame;          // refresh count of the frame that was composed at qpcCompose
    CFRAMES   cFrameSubmitted;        // DWM frame number that was last submitted
    UINT      cDXPresentSubmitted;    // DirectX present number that was last submitted
    CFRAMES   cFrameConfirmed;        // DWM frame number that was last confirmed as presented
    UINT      cDXPresentConfirmed;    // DirectX present number that was last confirmed as presented
    CFRAMES   cRefreshConfirmed;      // target refresh count of the last frame confirmed as completed by the GPU
    UINT      cDXRefreshConfirmed;    // DirectX refresh count when the frame was confirmed as presented
    CFRAMES   cFramesLate;            // number of frames the DWM presented late
    UINT      cFramesOutstanding;     // number of composition frames that have been issued but have not been confirmed as completed
    CFRAMES   cFrameDisplayed;        // last frame displayed
    QPC_TIME  qpcFrameDisplayed;      // QPC time of the composition pass when the frame was displayed
    CFRAMES   cRefreshFrameDisplayed; // vertical refresh count when the frame should have become visible
    CFRAMES   cFrameComplete;         // ID of the last frame marked as completed
    QPC_TIME  qpcFrameComplete;       // QPC time when the last frame was marked as completed
    CFRAMES   cFramePending;          // ID of the last frame marked as pending
    QPC_TIME  qpcFramePending;        // QPC time when the last frame was marked as pending
    CFRAMES   cFramesDisplayed;       // number of unique frames displayed
    CFRAMES   cFramesComplete;        // number of new completed frames that have been received
    CFRAMES   cFramesPending;         // number of new frames submitted to DirectX but not yet completed
    CFRAMES   cFramesAvailable;       // number of frames available but not displayed, used, or dropped
    CFRAMES   cFramesDropped;         // number of rendered frames that were never displayed because composition occurred too late
    CFRAMES   cFramesMissed;          // number of times an old frame was composed when a new frame should have been used but was not available
    CFRAMES   cRefreshNextDisplayed;  // frame count at which the next frame is scheduled to be displayed
    CFRAMES   cRefreshNextPresented;  // frame count at which the next DirectX present is scheduled to be displayed
    CFRAMES   cRefreshesDisplayed;    // total number of refreshes that have been displayed for the application since the DwmSetPresentParameters function was last called
    CFRAMES   cRefreshesPresented;    // total number of refreshes that have been presented by the application since DwmSetPresentParameters was last called
    CFRAMES   cRefreshStarted;        // refresh number when content for this window started to be displayed
    ULONGLONG cPixelsReceived;        // total number of pixels DirectX redirected to the DWM
    ULONGLONG cPixelsDrawn;           // number of pixels drawn
    CFRAMES   cBuffersEmpty;          // number of empty buffers in the flip chain
}
DWM_TIMING_INFO;

(注:为了在本站展示上面的源代码，假设在前面加上了以下缩写:)

typedef UNSIGNED_RATIO URATIO;
typedef DWM_FRAME_COUNT CFRAMES;

现在对于在窗口模式 中运行的应用程序，您当然可以随时获取这些详细信息。如果您只需要它进行被动分析，那么从 DwmGetCompositionTimingInfo 获取数据是现代的方式。

说到现代，因为这个问题暗示了现代化，您需要考虑使用从 IDXGISwapChain1 获得的 IDXGIFactory2::CreateSwapChainForComposition 来启用新的 DirectComposition 组件。

DirectComposition enables rich and fluid transitions by achieving a high framerate, using graphics hardware, and operating independently of the UI thread. DirectComposition can accept bitmap content drawn by different rendering libraries, including Microsoft DirectX bitmaps, and bitmaps rendered to a window (HWND bitmaps). Also, DirectComposition supports a variety of transformations, such as 2D affine transforms and 3D perspective transforms, as well as basic effects such as clipping and opacity.

无论如何，详细的计时信息似乎不太可能有用地告知应用程序的运行时行为； 也许它会帮助您预测您的下一个 VSync，但有人确实想知道“对消隐期的敏锐意识”对某些特定的人可能有什么意义DWM 控制的屏幕外交换链。

因为您的应用程序界面只是 DWM 处理的众多界面之一，所以 DWM 将在假设每个客户端行为一致的情况下自行进行各种动态调整。在这样的制度下，不可预测的适应是不合作的，最终可能只会混淆双方。

---

注意事项:
1.尽管后者建议使用 100 ns，但 QPC 的分辨率比 DateTime tick 的分辨率高许多数量级。单位面额。将 DateTime.Now.Ticks 视为(毫秒表示的)Environment.TickCount 的重新包装，但转换为 100 ns 单位。要获得尽可能高的分辨率，请使用静态方法 Stopwatch.GetTimestamp() 而不是 DateTime.Now.Ticks。