Question

我正在尝试设置并行多GPU离屏渲染上下文。我使用“OpenGL Insights”一书，第27章“NVIDIA Quadro上的多GPU渲染”。我也查看了wglCreateAffinityDCNV docs但仍然可以'把它钉住。

我的机器有2块NVidia Quadro 4000卡（无SLI）。运行在Windows 7 64bit上。我的工作流程如下：

使用GLFW创建默认窗口上下文。
映射GPU设备。
销毁默认的GLFW上下文。
为每个设备创建新的GL上下文（目前只尝试一个）
为每个上下文设置提升线程，并使其在该线程中保持最新状态。
分别在每个线程上运行渲染过程。（无资源共享）

创建的所有内容都没有错误并且运行但是一旦我尝试从屏幕外FBO读取像素，我就会在这里得到一个空指针：

GLubyte* ptr  = (GLubyte*)glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);

glError也返回“UNKNOWN ERROR”

我认为可能是多线程是问题但是在单线程上运行时相同的设置会给出相同的结果。所以我认为它与背景创作有关。

我是这样做的：

  ////Creating default window with GLFW here .
      .....
         .....

创建屏幕外环：

  PIXELFORMATDESCRIPTOR pfd =
{
    sizeof(PIXELFORMATDESCRIPTOR),
    1,
    PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,    //Flags
    PFD_TYPE_RGBA,            //The kind of framebuffer. RGBA or palette.
    24,                        //Colordepth of the framebuffer.
    0, 0, 0, 0, 0, 0,
    0,
    0,
    0,
    0, 0, 0, 0,
    24,                        //Number of bits for the depthbuffer
    8,                        //Number of bits for the stencilbuffer
    0,                        //Number of Aux buffers in the framebuffer.
    PFD_MAIN_PLANE,
    0,
    0, 0, 0
};

void  glMultiContext::renderingContext::createGPUContext(GPUEnum gpuIndex){

    int    pf;
    HGPUNV hGPU[MAX_GPU];
    HGPUNV GpuMask[MAX_GPU];

    UINT displayDeviceIdx;
    GPU_DEVICE gpuDevice;
    bool bDisplay, bPrimary;
    // Get a list of the first MAX_GPU GPUs in the system
    if ((gpuIndex < MAX_GPU) && wglEnumGpusNV(gpuIndex, &hGPU[gpuIndex])) {

        printf("Device# %d:\n", gpuIndex);

        // Now get the detailed information about this device:
        // how many displays it's attached to
        displayDeviceIdx = 0;
        if(wglEnumGpuDevicesNV(hGPU[gpuIndex], displayDeviceIdx, &gpuDevice))
        {   

            bPrimary |= (gpuDevice.Flags & DISPLAY_DEVICE_PRIMARY_DEVICE) != 0;
            printf(" Display# %d:\n", displayDeviceIdx);
            printf("  Name: %s\n",   gpuDevice.DeviceName);
            printf("  String: %s\n", gpuDevice.DeviceString);
            if(gpuDevice.Flags & DISPLAY_DEVICE_ATTACHED_TO_DESKTOP)
            {
                printf("  Attached to the desktop: LEFT=%d, RIGHT=%d, TOP=%d, BOTTOM=%d\n",
                    gpuDevice.rcVirtualScreen.left, gpuDevice.rcVirtualScreen.right, gpuDevice.rcVirtualScreen.top, gpuDevice.rcVirtualScreen.bottom);
            }
            else
            {
                printf("  Not attached to the desktop\n");
            }

            // See if it's the primary GPU
            if(gpuDevice.Flags & DISPLAY_DEVICE_PRIMARY_DEVICE)
            {
                printf("  This is the PRIMARY Display Device\n");
            }


        }

        ///=======================   CREATE a CONTEXT HERE 
        GpuMask[0] = hGPU[gpuIndex];
        GpuMask[1] = NULL;
        _affDC = wglCreateAffinityDCNV(GpuMask);

        if(!_affDC)
        {
            printf( "wglCreateAffinityDCNV failed");                  
        }

    }

    printf("GPU context created");
}

glMultiContext::renderingContext *
    glMultiContext::createRenderingContext(GPUEnum gpuIndex)
{
    glMultiContext::renderingContext *rc;

    rc = new renderingContext(gpuIndex);

    _pixelFormat = ChoosePixelFormat(rc->_affDC, &pfd);

    if(_pixelFormat == 0)
    {

        printf("failed to  choose pixel format");
        return false;
    }

     DescribePixelFormat(rc->_affDC, _pixelFormat, sizeof(pfd), &pfd);

    if(SetPixelFormat(rc->_affDC, _pixelFormat, &pfd) == FALSE)
    {
        printf("failed to set pixel format");
        return false;
    }

    rc->_affRC = wglCreateContext(rc->_affDC);


    if(rc->_affRC == 0)
    {
        printf("failed to create gl render context");
        return false;
    }


    return rc;
}

//Call at the end to make it current :


 bool glMultiContext::makeCurrent(renderingContext *rc)
{
    if(!wglMakeCurrent(rc->_affDC, rc->_affRC))
    {

        printf("failed to make context current");
        return false;
    }

    return true;
}

    ////  init OpenGL objects and rendering here :

     ..........
     ............

正如我所说，我在设备和上下文创建的任何阶段都没有出错。我究竟做错了什么？

更新

但是现在，如果我使用boost踏板生成另一个线程，我会收到初始错误。这是我的线程类：

GPUThread::GPUThread(void)
{
    _thread =NULL;
    _mustStop=false;
    _frame=0;


    _rc =glMultiContext::getInstance().createRenderingContext(GPU1);
    assert(_rc);

    glfwTerminate(); //terminate the initial window and context
    if(!glMultiContext::getInstance().makeCurrent(_rc)){

        printf("failed to make current!!!");
    }
             // init engine here (GLEW was already initiated)
    engine = new Engine(800,600,1);

}
void GPUThread::Start(){



    printf("threaded view setup ok");

    ///init thread here :
    _thread=new boost::thread(boost::ref(*this));

    _thread->join();

}
void GPUThread::Stop(){
    // Signal the thread to stop (thread-safe)
    _mustStopMutex.lock();
    _mustStop=true;
    _mustStopMutex.unlock();

    // Wait for the thread to finish.
    if (_thread!=NULL) _thread->join();

}
// Thread function
void GPUThread::operator () ()
{
    bool mustStop;

    do
    {
        // Display the next animation frame
        DisplayNextFrame();
        _mustStopMutex.lock();
        mustStop=_mustStop;
        _mustStopMutex.unlock();
    }   while (mustStop==false);

}


void GPUThread::DisplayNextFrame()
{

    engine->Render(); //renders frame
    if(_frame == 101){
        _mustStop=true;
    }
}

GPUThread::~GPUThread(void)
{
    delete _view;
    if(_rc != 0)
    {
        glMultiContext::getInstance().deleteRenderingContext(_rc);
        _rc = 0;
    }
    if(_thread!=NULL)delete _thread;
}

Answer 1

最后，我自己解决了这些问题。第一个问题是我将另一个设备上下文设置为当前后调用了glfwTerminate。这也许可以解决新的背景。第二个问题是我使用提升线程的“noobiness”。我无法在自定义线程中初始化所有与渲染相关的对象，因为我在设置线程之前调用了rc init对象过程，如上例所示。

在Windows上创建并行屏幕外OpenGL上下文

1 个答案: