文章目录
- 介绍
- 指定要创建的队列
- 指定使用的设备特性
- 创建逻辑设备
- 检索队列句柄
- 最终代码
介绍
在选择要使用的物理设备之后,我们需要设置一个逻辑设备来与它接口。逻辑设备创建过程类似于实例创建过程,并描述了我们想要使用的特性。在查询了哪些队列族可用之后,我们还需要指定要创建哪些队列。如果您有不同的需求,甚至可以从同一个物理设备创建多个逻辑设备。
首先添加一个新的类成员来存储逻辑设备句柄。
VkDevice device;
接下来,添加一个从initVulkan调用的createLogicalDevice函数。
void initVulkan() {
createInstance();
setupDebugMessenger();
pickPhysicalDevice();
createLogicalDevice();
}
void createLogicalDevice() {
}
指定要创建的队列
逻辑设备的创建涉及到在结构体中再次指定一堆细节,其中第一个将是VkDeviceQueueCreateInfo。该结构描述了单个队列族所需的队列数量。现在我们只对具有图形功能的队列感兴趣。
QueueFamilyIndices indices = findQueueFamilies(physicalDevice);
VkDeviceQueueCreateInfo queueCreateInfo{};
queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
queueCreateInfo.queueFamilyIndex = indices.graphicsFamily.value();
queueCreateInfo.queueCount = 1;
当前可用的驱动程序只允许您为每个队列族创建少量队列,实际上不需要多个队列。这是因为您可以在多个线程上创建所有命令缓冲区,然后通过一个低开销的调用在主线程上一次性提交它们。
Vulkan允许您使用0.0到1.0之间的浮点数为队列分配优先级,以影响命令缓冲区执行的调度。即使只有一个队列,这也是必需的:
float queuePriority = 1.0f;
queueCreateInfo.pQueuePriorities = &queuePriority;
指定使用的设备特性
下一个要指定的信息是我们将使用的设备特性集。这些是我们在前一章中查询过的vkGetPhysicalDeviceFeatures支持的特性,比如几何着色器。现在我们不需要任何特殊的东西,所以我们可以简单地定义它,并将所有内容留给VK_FALSE。当我们开始对Vulkan做更有趣的事情时,我们会回到这个结构。
VkPhysicalDeviceFeatures deviceFeatures{};
创建逻辑设备
有了前面的两个结构,我们可以开始填充主VkDeviceCreateInfo结构。
VkDeviceCreateInfo createInfo{};
createInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
首先为队列创建info和设备特性结构体添加指针:
createInfo.pQueueCreateInfos = &queueCreateInfo;
createInfo.queueCreateInfoCount = 1;
createInfo.pEnabledFeatures = &deviceFeatures;
其余的信息与VkInstanceCreateInfo结构类似,需要您指定扩展和验证层。不同的是,这一次这些是特定于设备的。
设备特定扩展的一个例子是VK_KHR_swapchain,它允许您从该设备向窗口呈现渲染的图像。系统中可能存在缺乏这种能力的Vulkan设备,例如,因为它们只支持计算操作。我们将在交换链章节中回到这个扩展。
Vulkan以前的实现区分了实例和设备特定的验证层,但现在不再是这样了。这意味着VkDeviceCreateInfo的enabledLayerCount和ppEnabledLayerNames字段被最新的实现忽略。然而,设置它们与旧的实现兼容仍然是一个好主意:
createInfo.enabledExtensionCount = 0;
if (enableValidationLayers) {
createInfo.enabledLayerCount = static_cast<uint32_t>(validationLayers.size());
createInfo.ppEnabledLayerNames = validationLayers.data();
} else {
createInfo.enabledLayerCount = 0;
}
我们现在不需要任何特定于设备的扩展。
就是这样,我们现在准备通过调用适当命名的vkCreateDevice函数来实例化逻辑设备。
if (vkCreateDevice(physicalDevice, &createInfo, nullptr, &device) != VK_SUCCESS) {
throw std::runtime_error("failed to create logical device!");
}
参数是要与之交互的物理设备、我们刚刚指定的队列和使用信息、可选的分配回调指针和指向存储逻辑设备句柄的变量的指针。与实例创建函数类似,此调用可以基于启用不存在的扩展或指定不受支持的特性的期望用法返回错误。
应该使用vkDestroyDevice函数在清理时销毁该设备:
void cleanup() {
vkDestroyDevice(device, nullptr);
...
}
逻辑设备不直接与实例交互,这就是它不作为参数包含的原因。
检索队列句柄
队列是与逻辑设备一起自动创建的,但是我们还没有一个句柄来与它们交互。首先添加一个类成员来存储图形队列的句柄:
VkQueue graphicsQueue;
当设备被销毁时,设备队列会被隐式清理,所以我们不需要在清理中做任何事情。
我们可以使用vkGetDeviceQueue函数来检索每个队列族的队列句柄。参数包括逻辑设备、队列族、队列索引和指向存储队列句柄的变量的指针。因为我们只从这个家族中创建一个队列,所以我们只使用索引0。
vkGetDeviceQueue(device, indices.graphicsFamily.value(), 0, &graphicsQueue);
有了逻辑设备和队列句柄,我们现在可以实际开始使用显卡做事情了!在接下来的几章中,我们将设置向窗口系统显示结果的资源。
最终代码
#define GLFW_INCLUDE_VULKAN
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdexcept>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <optional>
const uint32_t WIDTH = 800;
const uint32_t 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 {
std::optional<uint32_t> graphicsFamily;
bool isComplete() {
return graphicsFamily.has_value();
}
};
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.value();
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.value(), 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.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;
}
本文内容由网友自发贡献,版权归原作者所有,本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容,请联系:hwhale#tublm.com(使用前将#替换为@)