Vulkan填坑學習Day05—邏輯設備與隊列

Vulkan 邏輯設備與隊列

簡介

Vulkan 邏輯設備與隊列，在選擇要使用的物理設備之後，我們需要設置一個邏輯設備用於交互。邏輯設備創建過程與instance創建過程類似，也需要描述我們需要使用的功能。因爲我們已經查詢過哪些隊列簇可用，在這裏需要進一步爲邏輯設備創建具體類型的命令隊列。如果有不同的需求，也可以基於同一個物理設備創建多個邏輯設備。

首先添加一個新的類成員來存儲邏輯設備句柄。

VkDevice device;

接下來創建一個新的函數createLogicalDevice，並在initVulkan函數中調用，以創建邏輯設備。

void initVulkan() {
    createInstance();
    setupDebugCallback();
    pickPhysicalDevice();
    createLogicalDevice();
}

void createLogicalDevice() {
}

一、指定創建的隊列

創建邏輯設備需要在結構體中明確具體的信息，首先第一個結構體VkDeviceQueueCreateInfo。這個結構體描述隊列簇中預要申請使用的隊列數量。現在我們僅關心具備圖形能力的隊列。

QueueFamilyIndices indices = findQueueFamilies(physicalDevice);

VkDeviceQueueCreateInfo queueCreateInfo = {};
queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
queueCreateInfo.queueFamilyIndex = indices.graphicsFamily;
queueCreateInfo.queueCount = 1;

當前可用的驅動程序所提供的隊列簇只允許創建少量的隊列，並且很多時候沒有必要創建多個隊列。這是因爲可以在多個線程上創建所有命令緩衝區，然後在主線程一次性的以較低開銷的調用提交隊列。

Vulkan允許使用0.0到1.0之間的浮點數分配隊列優先級來影響命令緩衝區執行的調用。即使只有一個隊列也是必須的:

float queuePriority = 1.0f;
queueCreateInfo.pQueuePriorities = &queuePriority;

二、指定使用的設備特性

下一個要明確的信息有關設備要使用的功能特性。這些是我們在上一節中用vkGetPhysicalDeviceFeatures查詢支持的功能，比如geometry shaders。現在我們不需要任何特殊的功能，所以我們可以簡單的定義它並將所有內容保留到VK_FALSE。一旦我們要開始用Vulkan做更多的事情，我們會回到這個結構體，進一步設置。

VkPhysicalDeviceFeatures deviceFeatures = {};

三、創建邏輯設備

使用前面的兩個結構體，我們可以填充VkDeviceCreateInfo結構。

VkDeviceCreateInfo createInfo = {};
createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;

首先添加指向隊列創建信息的結構體和設備功能結構體:

createInfo.pQueueCreateInfos = &queueCreateInfo;
createInfo.queueCreateInfoCount = 1;
createInfo.pEnabledFeatures = &deviceFeatures;

結構體其餘的部分與VkInstanceCreateInfo相似，需要指定擴展和validation layers，總而言之這次不同之處是爲具體的設備設置信息。

設置具體擴展的一個案例是VK_KHR_swapchain，它允許將來自設備的渲染圖形呈現到Windows。系統中的Vulkan設備可能缺少該功能，例如僅僅支持計算操作。我們將在交換鏈章節中展開這個擴展。

就像之前validation layers小節中提到的，允許爲instance開啓validation layers，現在我們將爲設備開啓validation layers，而不需要爲設備指定任何擴展。

createInfo.enabledExtensionCount = 0;

if (enableValidationLayers) {
    createInfo.enabledLayerCount = static_cast<uint32_t>(validationLayers.size());
    createInfo.ppEnabledLayerNames = validationLayers.data();
} else {
    createInfo.enabledLayerCount = 0;
}

就這樣，我們現在可以通過調用vkCreateDevice函數來創建實例化邏輯設備。

if (vkCreateDevice(physicalDevice, &createInfo, nullptr, &device) != VK_SUCCESS) {
    throw std::runtime_error("failed to create logical device!");
}

這些參數分別是包含具體隊列使用信息的物理設備，可選的分配器回調指針以及用於存儲邏輯設備的句柄。與instance創建類似，此調用可能由於啓用不存在的擴展或者指定不支持的功能，導致返回錯誤。

在cleanup函數中邏輯設備需要調用vkDestroyDevice銷燬:

void cleanup() {
    vkDestroyDevice(device, nullptr);
    ...
}

邏輯設備不與instance交互，所以參數中不包含instance。

四、檢索隊列處理

這些隊列與邏輯設備自動的一同創建，但是我們還沒有一個與它們進行交互的句柄。在這裏添加一個新的類成員來存儲圖形隊列句柄:

VkQueue graphicsQueue;

設備隊列在設備被銷燬的時候隱式清理，所以我們不需要在cleanup函數中做任何操作。

我們可以使用vkGetDeviceQueue函數來檢測每個隊列簇中隊列的句柄。參數是邏輯設備，隊列簇，隊列索引和存儲獲取隊列變量句柄的指針。因爲我們只是從這個隊列簇創建一個隊列，所以需要使用索引 0。

vkGetDeviceQueue(device, indices.graphicsFamily, 0, &graphicsQueue);

在成功獲取邏輯設備和隊列句柄後，我們可以通過顯卡做一些實際的事情了，在接下來的幾章節中，我們會設置資源並將相應的結果提交到窗體系統。

附：源代碼

// logical_device.cpp
#define GLFW_INCLUDE_VULKAN
#include <GLFW/glfw3.h>

#include <iostream>
#include <stdexcept>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <optional>

const int WIDTH = 800;
const int HEIGHT = 600;

const std::vector<const char*> validationLayers = {
	"VK_LAYER_KHRONOS_validation"
};

#ifdef NDEBUG
const bool enableValidationLayers = false;
#else
const bool enableValidationLayers = true;
#endif

VkResult CreateDebugUtilsMessengerEXT(VkInstance instance, const VkDebugUtilsMessengerCreateInfoEXT* pCreateInfo, const VkAllocationCallbacks* pAllocator, VkDebugUtilsMessengerEXT* pDebugMessenger) {
	auto func = (PFN_vkCreateDebugUtilsMessengerEXT)vkGetInstanceProcAddr(instance, "vkCreateDebugUtilsMessengerEXT");
	if (func != nullptr) {
		return func(instance, pCreateInfo, pAllocator, pDebugMessenger);
	}
	else {
		return VK_ERROR_EXTENSION_NOT_PRESENT;
	}
}

void DestroyDebugUtilsMessengerEXT(VkInstance instance, VkDebugUtilsMessengerEXT debugMessenger, const VkAllocationCallbacks* pAllocator) {
	auto func = (PFN_vkDestroyDebugUtilsMessengerEXT)vkGetInstanceProcAddr(instance, "vkDestroyDebugUtilsMessengerEXT");
	if (func != nullptr) {
		func(instance, debugMessenger, pAllocator);
	}
}

struct QueueFamilyIndices {
	uint32_t graphicsFamily;

	bool isComplete() {
		return graphicsFamily >= 0;
	}
};

class HelloTriangleApplication {
public:
	void run() {
		initWindow();
		initVulkan();
		mainLoop();
		cleanup();
	}

private:
	GLFWwindow* window;

	VkInstance instance;
	VkDebugUtilsMessengerEXT debugMessenger;

	VkPhysicalDevice physicalDevice = VK_NULL_HANDLE;
	VkDevice device;

	VkQueue graphicsQueue;

	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();
		setupDebugMessenger();
		pickPhysicalDevice();
		createLogicalDevice();
	}

	void mainLoop() {
		while (!glfwWindowShouldClose(window)) {
			glfwPollEvents();
		}
	}

	void cleanup() {
		vkDestroyDevice(device, nullptr);

		if (enableValidationLayers) {
			DestroyDebugUtilsMessengerEXT(instance, debugMessenger, nullptr);
		}

		vkDestroyInstance(instance, nullptr);

		glfwDestroyWindow(window);

		glfwTerminate();
	}

	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 = static_cast<uint32_t>(extensions.size());
		createInfo.ppEnabledExtensionNames = extensions.data();

		VkDebugUtilsMessengerCreateInfoEXT debugCreateInfo;
		if (enableValidationLayers) {
			createInfo.enabledLayerCount = static_cast<uint32_t>(validationLayers.size());
			createInfo.ppEnabledLayerNames = validationLayers.data();

			populateDebugMessengerCreateInfo(debugCreateInfo);
			createInfo.pNext = (VkDebugUtilsMessengerCreateInfoEXT*)&debugCreateInfo;
		}
		else {
			createInfo.enabledLayerCount = 0;

			createInfo.pNext = nullptr;
		}

		if (vkCreateInstance(&createInfo, nullptr, &instance) != VK_SUCCESS) {
			throw std::runtime_error("failed to create instance!");
		}
	}

	void populateDebugMessengerCreateInfo(VkDebugUtilsMessengerCreateInfoEXT& createInfo) {
		createInfo = {};
		createInfo.sType = VK_STRUCTURE_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT;
		createInfo.messageSeverity = VK_DEBUG_UTILS_MESSAGE_SEVERITY_VERBOSE_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT;
		createInfo.messageType = VK_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT | VK_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT;
		createInfo.pfnUserCallback = debugCallback;
	}

	void setupDebugMessenger() {
		if (!enableValidationLayers) return;

		VkDebugUtilsMessengerCreateInfoEXT createInfo;
		populateDebugMessengerCreateInfo(createInfo);

		if (CreateDebugUtilsMessengerEXT(instance, &createInfo, nullptr, &debugMessenger) != VK_SUCCESS) {
			throw std::runtime_error("failed to set up debug messenger!");
		}
	}

	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<VkPhysicalDevice> 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);

		VkDeviceQueueCreateInfo queueCreateInfo = {};
		queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
		queueCreateInfo.queueFamilyIndex = indices.graphicsFamily;
		queueCreateInfo.queueCount = 1;

		float queuePriority = 1.0f;
		queueCreateInfo.pQueuePriorities = &queuePriority;

		VkPhysicalDeviceFeatures deviceFeatures = {};

		VkDeviceCreateInfo createInfo = {};
		createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;

		createInfo.pQueueCreateInfos = &queueCreateInfo;
		createInfo.queueCreateInfoCount = 1;

		createInfo.pEnabledFeatures = &deviceFeatures;

		createInfo.enabledExtensionCount = 0;

		if (enableValidationLayers) {
			createInfo.enabledLayerCount = static_cast<uint32_t>(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);
	}

	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<VkQueueFamilyProperties> 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;
			}

			if (indices.isComplete()) {
				break;
			}

			i++;
		}

		return indices;
	}

	std::vector<const char*> getRequiredExtensions() {
		uint32_t glfwExtensionCount = 0;
		const char** glfwExtensions;
		glfwExtensions = glfwGetRequiredInstanceExtensions(&glfwExtensionCount);

		std::vector<const char*> extensions(glfwExtensions, glfwExtensions + glfwExtensionCount);

		if (enableValidationLayers) {
			extensions.push_back(VK_EXT_DEBUG_UTILS_EXTENSION_NAME);
		}

		return extensions;
	}

	bool checkValidationLayerSupport() {
		uint32_t layerCount;
		vkEnumerateInstanceLayerProperties(&layerCount, nullptr);

		std::vector<VkLayerProperties> 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(VkDebugUtilsMessageSeverityFlagBitsEXT messageSeverity, VkDebugUtilsMessageTypeFlagsEXT messageType, const VkDebugUtilsMessengerCallbackDataEXT* pCallbackData, void* pUserData) {
		std::cerr << "validation layer: " << pCallbackData->pMessage << std::endl;

		return VK_FALSE;
	}
};

int main() {
	HelloTriangleApplication app;

	try {
		app.run();
	}
	catch (const std::exception& e) {
		std::cerr << e.what() << std::endl;
		return EXIT_FAILURE;
	}

	return EXIT_SUCCESS;
}