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

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：

VDeleter<VkSurfaceKHR> 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 :

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:

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 :

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:

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:

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:

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:

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;
}
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

createLogicalDevice(…)

的改变部分:

void createLogicalDevice() {
...
std::vector<VkDeviceQueueCreateInfo> 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);
}

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：

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

#include <iostream>
#include <stdexcept>
#include <functional>
#include <vector>
#include <cstring>
#include <set>

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 <typename T>
class VDeleter {
public:
VDeleter() : VDeleter([](T, VkAllocationCallbacks*) {}) {}

VDeleter(std::function<void(T, VkAllocationCallbacks*)> deletef) {
this->deleter = [=](T obj) { deletef(obj, nullptr); };
}

VDeleter(const VDeleter<VkInstance>& instance, std::function<void(VkInstance, T, VkAllocationCallbacks*)> deletef) {
this->deleter = [&instance, deletef](T obj) { deletef(instance, obj, nullptr); };
}

VDeleter(const VDeleter<VkDevice>& 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<VkInstance> instance{vkDestroyInstance};
VDeleter<VkDebugReportCallbackEXT> callback{instance, DestroyDebugReportCallbackEXT};
VDeleter<VkSurfaceKHR> surface{instance, vkDestroySurfaceKHR};

VkPhysicalDevice physicalDevice = VK_NULL_HANDLE;
VDeleter<VkDevice> 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<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);

std::vector<VkDeviceQueueCreateInfo> 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<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;
}

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<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(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;
}