欢迎来到第九篇！
在前八篇文章中，我们更像是在做一个"系统管理员"的工作：装驱动（Instance）、买显卡（Physical Device）、插线（Logical Device）、配显示器（Swap Chain/Image Views）。
现在，基础设施终于搭建完毕。我们要开始像一个"艺术家"一样思考了：我们要画画了。
但是在 Vulkan 中，你不能直接拿起笔就画。你必须先建立一条严密的工业流水线，告诉显卡：数据怎么进，怎么算，颜色怎么填，最后怎么出。这就是 Graphics Pipeline (图形管线)。
什么是图形管线？
简单来说，图形管线就是显卡内部的一条生产线。
-
原料： 顶点数据（一堆 3D 坐标、颜色）。
-
产品： 屏幕上的像素。
这个流程被切分成了很多个阶段。有些阶段是你可以编程控制的（Programmable ），有些是固定的但可配置的（Fixed-Function）。
让我们快速浏览一下画一个三角形必经的几个核心阶段：
-
Input Assembler (输入装配):
- 负责从内存里读取原始的顶点数据（比如三个点的坐标）。
-
Vertex Shader (顶点着色器) [可编程]:
-
这是我们要写的代码！
-
它的任务是处理每一个顶点。比如把 3D 坐标转换成屏幕上的 2D 坐标。
-
-
Rasterization (光栅化) [固定功能]:
- 把三个点连成三角形，并计算出这个三角形覆盖了屏幕上哪些像素。
-
Fragment Shader (片元/像素着色器) [可编程]:
-
这也是我们要写的代码！
-
它的任务是决定每个像素是什么颜色（红色？还是读取纹理颜色？）。
-
-
Color Blending (颜色混合) [固定功能]:
- 把计算出来的颜色和屏幕上原本的颜色混合（比如处理半透明）。
Vulkan 的"变态"之处：不可变状态
如果你用过 OpenGL，你可能习惯了这样写代码：
cpp
// OpenGL 伪代码
glUseProgram(shaderProgram);
glEnable(GL_DEPTH_TEST); // 开启深度测试
drawTriangle();
glDisable(GL_DEPTH_TEST); // 随时关闭
drawLine();在 OpenGL 中，你可以随时更改管线的任何状态，显卡驱动会在后台默默地为你重新配置硬件。这很方便，但性能开销巨大，因为驱动要不断地检查状态并重新编译指令。
Vulkan 彻底抛弃了这种做法。
在 Vulkan 中，图形管线 (VkPipeline) 是不可变的 (Immutable)。
这意味着：
-
你想开启深度测试？创建一个新管线。
-
你想把线条加宽？创建一个新管线。
-
你想换一个 Shader？创建一个新管线。
你必须在程序初始化阶段，就把你可能用到的所有"流水线配置"全部创建好（比如一个"实心渲染管线"，一个"线框渲染管线"）。在渲染循环中，你只需要切换管线对象即可。
核心哲学： 所有的复杂工作（编译、状态验证）都在初始化阶段完成（Setup 阶段），而渲染循环（Draw Loop）只做最简单的"切换"动作。这就是 Vulkan 高性能的秘诀。
完整代码：
cpp
#define GLFW_INCLUDE_VULKAN
#include <GLFW/glfw3.h>
#include <iostream>
#include <stdexcept>
#include <algorithm>
#include <vector>
#include <cstring>
#include <cstdlib>
#include <cstdint>
#include <limits>
#include <optional>
#include <set>
const uint32_t WIDTH = 800;
const uint32_t HEIGHT = 600;
const std::vector<const char*> validationLayers = {
"VK_LAYER_KHRONOS_validation"
};
const std::vector<const char*> deviceExtensions = {
VK_KHR_SWAPCHAIN_EXTENSION_NAME
};
#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;
std::optional<uint32_t> presentFamily;
bool isComplete() {
return graphicsFamily.has_value() && presentFamily.has_value();
}
};
struct SwapChainSupportDetails {
VkSurfaceCapabilitiesKHR capabilities;
std::vector<VkSurfaceFormatKHR> formats;
std::vector<VkPresentModeKHR> presentModes;
};
class HelloTriangleApplication {
public:
void run() {
initWindow();
initVulkan();
mainLoop();
cleanup();
}
private:
GLFWwindow* window;
VkInstance instance;
VkDebugUtilsMessengerEXT debugMessenger;
VkSurfaceKHR surface;
VkPhysicalDevice physicalDevice = VK_NULL_HANDLE;
VkDevice device;
VkQueue graphicsQueue;
VkQueue presentQueue;
VkSwapchainKHR swapChain;
std::vector<VkImage> swapChainImages;
VkFormat swapChainImageFormat;
VkExtent2D swapChainExtent;
std::vector<VkImageView> swapChainImageViews;
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();
createSurface();
pickPhysicalDevice();
createLogicalDevice();
createSwapChain();
createImageViews();
createGraphicsPipeline();
}
void mainLoop() {
while (!glfwWindowShouldClose(window)) {
glfwPollEvents();
}
}
void cleanup() {
for (auto imageView : swapChainImageViews) {
vkDestroyImageView(device, imageView, nullptr);
}
vkDestroySwapchainKHR(device, swapChain, nullptr);
vkDestroyDevice(device, nullptr);
if (enableValidationLayers) {
DestroyDebugUtilsMessengerEXT(instance, debugMessenger, nullptr);
}
vkDestroySurfaceKHR(instance, surface, 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 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<uint32_t> uniqueQueueFamilies = {indices.graphicsFamily.value(), indices.presentFamily.value()};
float queuePriority = 1.0f;
for (uint32_t 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.queueCreateInfoCount = static_cast<uint32_t>(queueCreateInfos.size());
createInfo.pQueueCreateInfos = queueCreateInfos.data();
createInfo.pEnabledFeatures = &deviceFeatures;
createInfo.enabledExtensionCount = static_cast<uint32_t>(deviceExtensions.size());
createInfo.ppEnabledExtensionNames = deviceExtensions.data();
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);
vkGetDeviceQueue(device, indices.presentFamily.value(), 0, &presentQueue);
}
void createSwapChain() {
SwapChainSupportDetails swapChainSupport = querySwapChainSupport(physicalDevice);
VkSurfaceFormatKHR surfaceFormat = chooseSwapSurfaceFormat(swapChainSupport.formats);
VkPresentModeKHR presentMode = chooseSwapPresentMode(swapChainSupport.presentModes);
VkExtent2D extent = chooseSwapExtent(swapChainSupport.capabilities);
uint32_t imageCount = swapChainSupport.capabilities.minImageCount + 1;
if (swapChainSupport.capabilities.maxImageCount > 0 && imageCount > swapChainSupport.capabilities.maxImageCount) {
imageCount = swapChainSupport.capabilities.maxImageCount;
}
VkSwapchainCreateInfoKHR createInfo{};
createInfo.sType = VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR;
createInfo.surface = surface;
createInfo.minImageCount = imageCount;
createInfo.imageFormat = surfaceFormat.format;
createInfo.imageColorSpace = surfaceFormat.colorSpace;
createInfo.imageExtent = extent;
createInfo.imageArrayLayers = 1;
createInfo.imageUsage = VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT;
QueueFamilyIndices indices = findQueueFamilies(physicalDevice);
uint32_t queueFamilyIndices[] = {indices.graphicsFamily.value(), indices.presentFamily.value()};
if (indices.graphicsFamily != indices.presentFamily) {
createInfo.imageSharingMode = VK_SHARING_MODE_CONCURRENT;
createInfo.queueFamilyIndexCount = 2;
createInfo.pQueueFamilyIndices = queueFamilyIndices;
} else {
createInfo.imageSharingMode = VK_SHARING_MODE_EXCLUSIVE;
}
createInfo.preTransform = swapChainSupport.capabilities.currentTransform;
createInfo.compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
createInfo.presentMode = presentMode;
createInfo.clipped = VK_TRUE;
createInfo.oldSwapchain = VK_NULL_HANDLE;
if (vkCreateSwapchainKHR(device, &createInfo, nullptr, &swapChain) != VK_SUCCESS) {
throw std::runtime_error("failed to create swap chain!");
}
vkGetSwapchainImagesKHR(device, swapChain, &imageCount, nullptr);
swapChainImages.resize(imageCount);
vkGetSwapchainImagesKHR(device, swapChain, &imageCount, swapChainImages.data());
swapChainImageFormat = surfaceFormat.format;
swapChainExtent = extent;
}
void createImageViews() {
swapChainImageViews.resize(swapChainImages.size());
for (size_t i = 0; i < swapChainImages.size(); i++) {
VkImageViewCreateInfo createInfo{};
createInfo.sType = VK_STRUCTURE_TYPE_IMAGE_VIEW_CREATE_INFO;
createInfo.image = swapChainImages[i];
createInfo.viewType = VK_IMAGE_VIEW_TYPE_2D;
createInfo.format = swapChainImageFormat;
createInfo.components.r = VK_COMPONENT_SWIZZLE_IDENTITY;
createInfo.components.g = VK_COMPONENT_SWIZZLE_IDENTITY;
createInfo.components.b = VK_COMPONENT_SWIZZLE_IDENTITY;
createInfo.components.a = VK_COMPONENT_SWIZZLE_IDENTITY;
createInfo.subresourceRange.aspectMask = VK_IMAGE_ASPECT_COLOR_BIT;
createInfo.subresourceRange.baseMipLevel = 0;
createInfo.subresourceRange.levelCount = 1;
createInfo.subresourceRange.baseArrayLayer = 0;
createInfo.subresourceRange.layerCount = 1;
if (vkCreateImageView(device, &createInfo, nullptr, &swapChainImageViews[i]) != VK_SUCCESS) {
throw std::runtime_error("failed to create image views!");
}
}
}
void createGraphicsPipeline() {
}
VkSurfaceFormatKHR chooseSwapSurfaceFormat(const std::vector<VkSurfaceFormatKHR>& availableFormats) {
for (const auto& availableFormat : availableFormats) {
if (availableFormat.format == VK_FORMAT_B8G8R8A8_SRGB && availableFormat.colorSpace == VK_COLOR_SPACE_SRGB_NONLINEAR_KHR) {
return availableFormat;
}
}
return availableFormats[0];
}
VkPresentModeKHR chooseSwapPresentMode(const std::vector<VkPresentModeKHR>& availablePresentModes) {
for (const auto& availablePresentMode : availablePresentModes) {
if (availablePresentMode == VK_PRESENT_MODE_MAILBOX_KHR) {
return availablePresentMode;
}
}
return VK_PRESENT_MODE_FIFO_KHR;
}
VkExtent2D chooseSwapExtent(const VkSurfaceCapabilitiesKHR& capabilities) {
if (capabilities.currentExtent.width != std::numeric_limits<uint32_t>::max()) {
return capabilities.currentExtent;
} else {
int width, height;
glfwGetFramebufferSize(window, &width, &height);
VkExtent2D actualExtent = {
static_cast<uint32_t>(width),
static_cast<uint32_t>(height)
};
actualExtent.width = std::clamp(actualExtent.width, capabilities.minImageExtent.width, capabilities.maxImageExtent.width);
actualExtent.height = std::clamp(actualExtent.height, capabilities.minImageExtent.height, capabilities.maxImageExtent.height);
return actualExtent;
}
}
SwapChainSupportDetails querySwapChainSupport(VkPhysicalDevice device) {
SwapChainSupportDetails details;
vkGetPhysicalDeviceSurfaceCapabilitiesKHR(device, surface, &details.capabilities);
uint32_t formatCount;
vkGetPhysicalDeviceSurfaceFormatsKHR(device, surface, &formatCount, nullptr);
if (formatCount != 0) {
details.formats.resize(formatCount);
vkGetPhysicalDeviceSurfaceFormatsKHR(device, surface, &formatCount, details.formats.data());
}
uint32_t presentModeCount;
vkGetPhysicalDeviceSurfacePresentModesKHR(device, surface, &presentModeCount, nullptr);
if (presentModeCount != 0) {
details.presentModes.resize(presentModeCount);
vkGetPhysicalDeviceSurfacePresentModesKHR(device, surface, &presentModeCount, details.presentModes.data());
}
return details;
}
bool isDeviceSuitable(VkPhysicalDevice device) {
QueueFamilyIndices indices = findQueueFamilies(device);
bool extensionsSupported = checkDeviceExtensionSupport(device);
bool swapChainAdequate = false;
if (extensionsSupported) {
SwapChainSupportDetails swapChainSupport = querySwapChainSupport(device);
swapChainAdequate = !swapChainSupport.formats.empty() && !swapChainSupport.presentModes.empty();
}
return indices.isComplete() && extensionsSupported && swapChainAdequate;
}
bool checkDeviceExtensionSupport(VkPhysicalDevice device) {
uint32_t extensionCount;
vkEnumerateDeviceExtensionProperties(device, nullptr, &extensionCount, nullptr);
std::vector<VkExtensionProperties> availableExtensions(extensionCount);
vkEnumerateDeviceExtensionProperties(device, nullptr, &extensionCount, availableExtensions.data());
std::set<std::string> requiredExtensions(deviceExtensions.begin(), deviceExtensions.end());
for (const auto& extension : availableExtensions) {
requiredExtensions.erase(extension.extensionName);
}
return requiredExtensions.empty();
}
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;
}
VkBool32 presentSupport = false;
vkGetPhysicalDeviceSurfaceSupportKHR(device, i, surface, &presentSupport);
if (presentSupport) {
indices.presentFamily = 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;
}我们接下来要面对的挑战
为了画出那个简单的三角形，我们需要手动配置上述每一个阶段。接下来的教程将分为以下几个硬核部分：
-
Shader Modules: 编写 GLSL 代码并将其编译为 SPIR-V 字节码。
-
Fixed Functions: 配置视口、多重采样、深度测试、颜色混合等固定阶段。
-
Pipeline Layout: 告诉管线我们会传入哪些全局变量（Uniforms）。
-
Render Pass: 告诉管线我们要渲染到哪个 Framebuffer，以及渲染前后怎么处理显存。
是不是听起来很多？确实很多。创建管线的 VkGraphicsPipelineCreateInfo 结构体可能是 Vulkan 中最庞大的结构体之一。
但是，一旦你跨过了这座大山，你就真正掌握了 GPU 的控制权。
下一步
理论课结束。下一篇，我们要从"C++ 程序员"暂时转职为"Shader 程序员"。
我们将编写两个小程序：顶点着色器 （告诉显卡三角形的三个角在哪里）和片元着色器 （告诉显卡三角形是什么颜色）。并且，我们将第一次接触 Vulkan 的官方着色器语言标准 ------ SPIR-V。
准备好安装编译器了吗？