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vulakn教程--Drawing a Triangle--Presentation--Window surface

发表于2016-12-09
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原文链接: Vulkan-tutorial

Window surface

因为Vulkan是平台(platform)无关的，它不能直接与平台窗体系统(window system)进行通信，为了连接Vulkan和窗体系统,使得被渲染后的结果显示到屏幕上，我们需要使用WSI扩展(Window System Integration extensions),在这个章节我们将使用VK_KHR_surface，它提供的VkSurfaceKHR 是对surface的一个抽象，使得我们能够将渲染后的结果放到VkSurfaceKHR上。还记得我们在之前使用GLFW创建的window吗，window将支持VkSurfaceKHR的创建。

VK_KHR_surface是一个Instance 级别的扩展，我们在创建Instance时已经通过glfwGetRequiredInstanceExtensions允许了这个扩展。

事实上，window surface的创建应该在Instance创建之后就应该完成，因为它会影响Physical Device的选取，之所以推迟到现在才讲，是因为window surface是关于渲染目标和显示的(render targets and presentation)一个比较大的话题，它会扰乱你对其他概念的理解。而且你要明白，如果你只是需要off-screen rendering，那么window surface对于Vulkan来说只是一个可选的扩展。

创建VkSurfaceKHR

声明：

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VDeleter surface{instance, vkDestroySurfaceKHR};

如果我们在Windows上创建VkSurfaceKHR ，我们需要两个句柄: HWND 和HMODULE，并需要VK_KHR_win32_surface扩展，其实我们已经通过glfwGetRequiredInstanceExtensions允许了这个扩展，然后我们需要填充下面这个结构 :

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VkWin32SurfaceCreateInfoKHR createInfo;
createInfo.sType = VK_STRUCTURE_TYPE_WIN32_SURFACE_CREATE_INFO_KHR;
createInfo.hwnd = glfwGetWin32Window(window);
createInfo.hinstance = GetModuleHandle(nullptr);

然后创建基于windows的surface:

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auto CreateWin32SurfaceKHR = (PFN_vkCreateWin32SurfaceKHR) vkGetInstanceProcAddr(instance, "vkCreateWin32SurfaceKHR");
 
if (!CreateWin32SurfaceKHR || CreateWin32SurfaceKHR(instance, &createInfo,
        nullptr, &surface) != VK_SUCCESS) {
    throw std::runtime_error("failed to create window surface!");
}

但是我们不会这么犯傻，因为我们用的可是GLFW啊(GLFW是跨平台的)，我们没有必要去写一个基于特定平台的代码，而且这简直毫无道理。事实上，GLFW提供了glfwCreateWindowSurface方法，它自动为我们解决平台的差异性。

所以surface的创建应该是这样的 :

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void createSurface() {
    if (glfwCreateWindowSurface(instance, window, nullptr, &surface) != VK_SUCCESS) {
        throw std::runtime_error("failed to create window surface!");
    }
}

就是这么简单优雅！

确定显卡支持WSI(请求显示支持)

尽管Vulkan的实现可能支持WSI ，但并不代表你平台上的所有显卡也支持，它是指Physical Device 中存在一种将images提交到Surface上的命令队列。因此我们需要扩展下面这个函数:

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bool isDeviceSuitable(VkPhysicalDevice device) {
    QueueFamilyIndices indices = findQueueFamilies(device);
 
    return indices.isComplete();
}

注：这个函数其实并未修改。

我们修改isDeviceSuitable(…)的目的是确保能够将渲染好的图片(images)提交(present)到我们所创建的surface上。又因为显示(presentation)是基于队列的，那么问题就转换为:从显卡里寻找一种具有将渲染结果提交(presenting)到surface上的命令的队列(queue family)。

绘画命令和显示命令可能不重叠在一种队列，所以我们需要修改一下结构:

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struct QueueFamilyIndices {
    int graphicsFamily = -1;
    int presentFamily = -1;
 
    bool isComplete() {
        return graphicsFamily >= 0 && presentFamily >= 0;
    }
};

接下来，为了检测队列是否支持将渲染结果提交(presenting)到surface上，我们使用:

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VkResult vkGetPhysicalDeviceSurfaceSupportKHR(
    VkPhysicalDevice physicalDevice,
    uint32_t queueFamilyIndex,
    VkSurfaceKHR surface,
    VkBool32* pSupported);

这里不做解释，参数已经见名知意了。

联合以上思想，findQueueFamilies(…) 将变成下面这个样子:

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QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
    QueueFamilyIndices indices;
 
    uint32_t queueFamilyCount = 0;
    vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, nullptr);
 
    std::vector queueFamilies(queueFamilyCount);
    vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, queueFamilies.data());
 
    int i = 0;
    for (const auto& queueFamily : queueFamilies) {
        if (queueFamily.queueCount > 0 && queueFamily.queueFlags & VK_QUEUE_GRAPHICS_BIT) {
            indices.graphicsFamily = i;
        }
        VkBool32 presentSupport = false;
        vkGetPhysicalDeviceSurfaceSupportKHR(device, i, surface, &presentSupport);
 
        if (queueFamily.queueCount > 0 && presentSupport) {
            indices.presentFamily = i;
        }
 
        if (indices.isComplete()) {
            break;
        }
 
        i++;
    }
    return indices;
}

注意，我们在创建Logical Device时已经创建了一个队列用于支持图形处理的graphicsQueue，现在我们变更了需求，又多了一个用于将渲染结果提交(presenting)到surface上的队列。 那么，Logical Device的创建过程也需要改变。

获取presentQueue:

VkQueue presentQueue; //声明
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VkQueue presentQueue;  //声明

createLogicalDevice(…)的改变部分:

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void createLogicalDevice() {
        ...
        std::vector queueCreateInfos;
        std::set<int> uniqueQueueFamilies = {indices.graphicsFamily, indices.presentFamily};
 
        float queuePriority = 1.0f;
        for (int queueFamily : uniqueQueueFamilies) {
            VkDeviceQueueCreateInfo queueCreateInfo = {};
            queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
            queueCreateInfo.queueFamilyIndex = queueFamily;
            queueCreateInfo.queueCount = 1;
            queueCreateInfo.pQueuePriorities = &queuePriority;
            queueCreateInfos.push_back(queueCreateInfo);
        }
        ...
        VkDeviceCreateInfo createInfo = {};
        createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
 
        createInfo.pQueueCreateInfos = queueCreateInfos.data();
        createInfo.queueCreateInfoCount = (uint32_t) queueCreateInfos.size();
        createInfo.pEnabledFeatures = &deviceFeatures;
        createInfo.enabledExtensionCount = 0;     
        ...
        ...
        vkGetDeviceQueue(device, indices.presentFamily, 0, &presentQueue);
    }int>

如果presentFamily和graphicsFamily是同一种队列，presentQueue和graphicsQueue将指向同一个对象。

注：在我的平台上，它们两个是一个队列。

源码：

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#define GLFW_INCLUDE_VULKAN
#include
 
#include
#include
#include
#include
#include
#include
 
const int WIDTH = 800;
const int HEIGHT = 600;
 
const std::vector<const char*=""> validationLayers = {
    "VK_LAYER_LUNARG_standard_validation"
};
 
#ifdef NDEBUG
const bool enableValidationLayers = false;
#else
const bool enableValidationLayers = true;
#endif
 
VkResult CreateDebugReportCallbackEXT(VkInstance instance, const VkDebugReportCallbackCreateInfoEXT* pCreateInfo, const VkAllocationCallbacks* pAllocator, VkDebugReportCallbackEXT* pCallback) {
    auto func = (PFN_vkCreateDebugReportCallbackEXT) vkGetInstanceProcAddr(instance, "vkCreateDebugReportCallbackEXT");
    if (func != nullptr) {
        return func(instance, pCreateInfo, pAllocator, pCallback);
    } else {
        return VK_ERROR_EXTENSION_NOT_PRESENT;
    }
}
 
void DestroyDebugReportCallbackEXT(VkInstance instance, VkDebugReportCallbackEXT callback, const VkAllocationCallbacks* pAllocator) {
    auto func = (PFN_vkDestroyDebugReportCallbackEXT) vkGetInstanceProcAddr(instance, "vkDestroyDebugReportCallbackEXT");
    if (func != nullptr) {
        func(instance, callback, pAllocator);
    }
}
 
template "">
class VDeleter {
public:
    VDeleter() : VDeleter([](T, VkAllocationCallbacks*) {}) {}
 
    VDeleter(std::function<void(t, vkallocationcallbacks*)=""> deletef) {
        this->deleter = [=](T obj) { deletef(obj, nullptr); };
    }
 
    VDeleter(const VDeleter& instance, std::function<void(vkinstance, t,="" vkallocationcallbacks*)=""> deletef) {
        this->deleter = [&instance, deletef](T obj) { deletef(instance, obj, nullptr); };
    }
 
    VDeleter(const VDeleter& device, std::function<void(vkdevice, t,="" vkallocationcallbacks*)=""> deletef) {
        this->deleter = [&device, deletef](T obj) { deletef(device, obj, nullptr); };
    }
 
    ~VDeleter() {
        cleanup();
    }
 
    T* operator &() {
        cleanup();
        return &object;
    }
 
    operator T() const {
        return object;
    }
 
private:
    T object{VK_NULL_HANDLE};
    std::function<void(t)> deleter;
 
    void cleanup() {
        if (object != VK_NULL_HANDLE) {
            deleter(object);
        }
        object = VK_NULL_HANDLE;
    }
};
 
struct QueueFamilyIndices {
    int graphicsFamily = -1;
    int presentFamily = -1;
 
    bool isComplete() {
        return graphicsFamily >= 0 && presentFamily >= 0;
    }
};
 
class HelloTriangleApplication {
public:
    void run() {
        initWindow();
        initVulkan();
        mainLoop();
    }
 
private:
    GLFWwindow* window;
 
    VDeleter instance{vkDestroyInstance};
    VDeleter callback{instance, DestroyDebugReportCallbackEXT};
    VDeleter surface{instance, vkDestroySurfaceKHR};
 
    VkPhysicalDevice physicalDevice = VK_NULL_HANDLE;
    VDeleter device{vkDestroyDevice};
 
    VkQueue graphicsQueue;
    VkQueue presentQueue;
 
    void initWindow() {
        glfwInit();
 
        glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
        glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
 
        window = glfwCreateWindow(WIDTH, HEIGHT, "Vulkan", nullptr, nullptr);
    }
 
    void initVulkan() {
        createInstance();
        setupDebugCallback();
        createSurface();
        pickPhysicalDevice();
        createLogicalDevice();
    }
 
    void mainLoop() {
        while (!glfwWindowShouldClose(window)) {
            glfwPollEvents();
        }
    }
 
    void createInstance() {
        if (enableValidationLayers && !checkValidationLayerSupport()) {
            throw std::runtime_error("validation layers requested, but not available!");
        }
 
        VkApplicationInfo appInfo = {};
        appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
        appInfo.pApplicationName = "Hello Triangle";
        appInfo.applicationVersion = VK_MAKE_VERSION(1, 0, 0);
        appInfo.pEngineName = "No Engine";
        appInfo.engineVersion = VK_MAKE_VERSION(1, 0, 0);
        appInfo.apiVersion = VK_API_VERSION_1_0;
 
        VkInstanceCreateInfo createInfo = {};
        createInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
        createInfo.pApplicationInfo = &appInfo;
 
        auto extensions = getRequiredExtensions();
        createInfo.enabledExtensionCount = extensions.size();
        createInfo.ppEnabledExtensionNames = extensions.data();
 
        if (enableValidationLayers) {
            createInfo.enabledLayerCount = validationLayers.size();
            createInfo.ppEnabledLayerNames = validationLayers.data();
        } else {
            createInfo.enabledLayerCount = 0;
        }
 
        if (vkCreateInstance(&createInfo, nullptr, &instance) != VK_SUCCESS) {
            throw std::runtime_error("failed to create instance!");
        }
    }
 
    void setupDebugCallback() {
        if (!enableValidationLayers) return;
 
        VkDebugReportCallbackCreateInfoEXT createInfo = {};
        createInfo.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT;
        createInfo.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT;
        createInfo.pfnCallback = debugCallback;
 
        if (CreateDebugReportCallbackEXT(instance, &createInfo, nullptr, &callback) != VK_SUCCESS) {
            throw std::runtime_error("failed to set up debug callback!");
        }
    }
 
    void createSurface() {
        if (glfwCreateWindowSurface(instance, window, nullptr, &surface) != VK_SUCCESS) {
            throw std::runtime_error("failed to create window surface!");
        }
    }
 
    void pickPhysicalDevice() {
        uint32_t deviceCount = 0;
        vkEnumeratePhysicalDevices(instance, &deviceCount, nullptr);
 
        if (deviceCount == 0) {
            throw std::runtime_error("failed to find GPUs with Vulkan support!");
        }
 
        std::vector devices(deviceCount);
        vkEnumeratePhysicalDevices(instance, &deviceCount, devices.data());
 
        for (const auto& device : devices) {
            if (isDeviceSuitable(device)) {
                physicalDevice = device;
                break;
            }
        }
 
        if (physicalDevice == VK_NULL_HANDLE) {
            throw std::runtime_error("failed to find a suitable GPU!");
        }
    }
 
    void createLogicalDevice() {
        QueueFamilyIndices indices = findQueueFamilies(physicalDevice);
 
        std::vector queueCreateInfos;
        std::set<int> uniqueQueueFamilies = {indices.graphicsFamily, indices.presentFamily};
 
        float queuePriority = 1.0f;
        for (int queueFamily : uniqueQueueFamilies) {
            VkDeviceQueueCreateInfo queueCreateInfo = {};
            queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
            queueCreateInfo.queueFamilyIndex = queueFamily;
            queueCreateInfo.queueCount = 1;
            queueCreateInfo.pQueuePriorities = &queuePriority;
            queueCreateInfos.push_back(queueCreateInfo);
        }
 
        VkPhysicalDeviceFeatures deviceFeatures = {};
 
        VkDeviceCreateInfo createInfo = {};
        createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
 
        createInfo.pQueueCreateInfos = queueCreateInfos.data();
        createInfo.queueCreateInfoCount = (uint32_t) queueCreateInfos.size();
 
        createInfo.pEnabledFeatures = &deviceFeatures;
 
        createInfo.enabledExtensionCount = 0;
 
        if (enableValidationLayers) {
            createInfo.enabledLayerCount = validationLayers.size();
            createInfo.ppEnabledLayerNames = validationLayers.data();
        } else {
            createInfo.enabledLayerCount = 0;
        }
 
        if (vkCreateDevice(physicalDevice, &createInfo, nullptr, &device) != VK_SUCCESS) {
            throw std::runtime_error("failed to create logical device!");
        }
 
        vkGetDeviceQueue(device, indices.graphicsFamily, 0, &graphicsQueue);
        vkGetDeviceQueue(device, indices.presentFamily, 0, &presentQueue);
    }
 
    bool isDeviceSuitable(VkPhysicalDevice device) {
        QueueFamilyIndices indices = findQueueFamilies(device);
 
        return indices.isComplete();
    }
 
    QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
        QueueFamilyIndices indices;
 
        uint32_t queueFamilyCount = 0;
        vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, nullptr);
 
        std::vector queueFamilies(queueFamilyCount);
        vkGetPhysicalDeviceQueueFamilyProperties(device, &queueFamilyCount, queueFamilies.data());
 
        int i = 0;
        for (const auto& queueFamily : queueFamilies) {
            if (queueFamily.queueCount > 0 && queueFamily.queueFlags & VK_QUEUE_GRAPHICS_BIT) {
                indices.graphicsFamily = i;
            }
 
            VkBool32 presentSupport = false;
            vkGetPhysicalDeviceSurfaceSupportKHR(device, i, surface, &presentSupport);
 
            if (queueFamily.queueCount > 0 && presentSupport) {
                indices.presentFamily = i;
            }
 
            if (indices.isComplete()) {
                break;
            }
 
            i++;
        }
 
        return indices;
    }
 
    std::vector<const char*=""> getRequiredExtensions() {
        std::vector<const char*=""> extensions;
 
        unsigned int glfwExtensionCount = 0;
        const char** glfwExtensions;
        glfwExtensions = glfwGetRequiredInstanceExtensions(&glfwExtensionCount);
 
        for (unsigned int i = 0; i < glfwExtensionCount; i++) {
            extensions.push_back(glfwExtensions[i]);
        }
 
        if (enableValidationLayers) {
            extensions.push_back(VK_EXT_DEBUG_REPORT_EXTENSION_NAME);
        }
 
        return extensions;
    }
 
    bool checkValidationLayerSupport() {
        uint32_t layerCount;
        vkEnumerateInstanceLayerProperties(&layerCount, nullptr);
 
        std::vector availableLayers(layerCount);
        vkEnumerateInstanceLayerProperties(&layerCount, availableLayers.data());
 
        for (const char* layerName : validationLayers) {
            bool layerFound = false;
 
            for (const auto& layerProperties : availableLayers) {
                if (strcmp(layerName, layerProperties.layerName) == 0) {
                    layerFound = true;
                    break;
                }
            }
 
            if (!layerFound) {
                return false;
            }
        }
 
        return true;
    }
 
    static VKAPI_ATTR VkBool32 VKAPI_CALL debugCallback(VkDebugReportFlagsEXT flags, VkDebugReportObjectTypeEXT objType, uint64_t obj, size_t location, int32_t code, const char* layerPrefix, const char* msg, void* userData) {
        std::cerr << "validation layer: " << msg << std::endl;
 
        return VK_FALSE;
    }
};
 
int main() {
    HelloTriangleApplication app;
 
    try {
        app.run();
    } catch (const std::runtime_error& e) {
        std::cerr << e.what() << std::endl;
        return EXIT_FAILURE;
    }
 
    return EXIT_SUCCESS;
}const>const>int>void(t)>void(vkdevice,>void(vkinstance,>void(t,>const>set>

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