Direct3D 12窗口模式强制vsync

Direct3D 12 windowed mode forces vsync

本文关键字：vsync 模式 窗口 Direct3D      更新时间：2023-10-16

我正在编写一个简单的Direct3D 12应用程序，为Vulkan的发布做准备，它在所有方面都能正常工作，但有一点除外：在有边框的窗口中运行会将帧速率限制在60fps，即使禁用了vsync。让我困惑的是：同一个程序在全屏窗口中的运行速度接近4000帧/秒。

使用一个脏兮兮的自制探查器，我发现在我的代码的这一部分出现了挂起，它一直等到最后一帧完成后才开始处理下一帧。

if (m_fence->GetCompletedValue() < endFenceValue)
{
    result = m_fence->SetEventOnCompletion(endFenceValue, m_fenceEvent);
    if (result != S_OK) return false;
    WaitForSingleObject(m_fenceEvent, INFINITE); //Program stalls here
}
//m_fence is a pointer to an ID3D12Fence object
//endFenceValue is an unsigned long long
//m_fenceEvent is a HANDLE

用于呈现渲染帧的代码是普通的：

if (m_vsync)
{
    result = m_swapChain->Present(1, 0);
    if (result != S_OK) return 0;
}
else
{
    result = m_swapChain->Present(0, 0);
    if (result != S_OK) return 0;
}
//Increase the fence value
result = m_commandQueue->Signal(m_fence, m_fenceValue);
if (result != S_OK) return 0;
return m_fenceValue++;
//m_swapChain is a pointer to an IDXGISwapChain3 object
//m_commandQueue is a pointer to an ID3D12CommandQueue object
//m_fenceValue is a HANDLE

注意：第一个代码块使用上述函数的返回值endFenceValue。

我使用的交换链是这样设置的：

swapChainDesc.BufferCount = 2; //Double buffered
swapChainDesc.BufferDesc.Width = width; //Set width
swapChainDesc.BufferDesc.Height = height; //Set height
swapChainDesc.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; //32-bit back buffers
swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; //Set the back buffers to be used as render targets
swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_DISCARD; //Throw out old back buffer contents after getting a new frame
swapChainDesc.OutputWindow = window;
swapChainDesc.Windowed = !fullscreen;
//Auto-detect the refresh rate
swapChainDesc.BufferDesc.RefreshRate.Numerator = 0;
swapChainDesc.BufferDesc.RefreshRate.Denominator = 0;
//No multisampling for now
swapChainDesc.SampleDesc.Count = 1;
swapChainDesc.SampleDesc.Quality = 0;
//Set the scan line ordering and scaling to unspecified
swapChainDesc.BufferDesc.ScanlineOrdering = DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
swapChainDesc.BufferDesc.Scaling = DXGI_MODE_SCALING_UNSPECIFIED;
//Allow to switch between windowed and fullscreen modes
//Also changes the monitor resolution to match the width and height of the window in fullscreen mode
swapChainDesc.Flags = DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH;

对于那些感兴趣的人，我使用SDL来创建窗口，但编写自己的WinMain并没有解决问题。我还尝试在英伟达控制面板中检查我的vsync设置，退出fl.ux（但没有卸载），并在系统属性中更改我的性能设置。

有人能对此提供解释或解决方案吗？

windows 10构建版本10586取消了带窗口交换链的刷新率上限。

更新你的窗口，它应该会自行解决。

根据nVidia Developer Zone的说法，这实际上是预期行为。目前，拥有无上限帧速率的唯一方法是使用全屏窗口。

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