CMake创建跨平台OPenGL工程(学习笔记)

一、跨平台环境基本配置

1、环境搭建

1）linux OpenGL环境搭建参考：ubuntu18.04 OpenGL开发（显示YUV）_ubuntu opengl-CSDN博客

https://blog.51cto.com/cerana/6433535

2）windows下环境搭建

OpenGL+Visual Studio2022+GLFW+glad详细配置教程_给vs配置glfw和glad-CSDN博客

2、创建cmake

这里测试使用的图形界面使用QT。其中路径后面讲解。

主要有几个注意事项：

1）linux下需要添加

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wno-error=register")

2）windows下需要设置vitual studio

set(LIBRARY_GLFW_PATH "${PROJECT_SOURCE_DIR}/lib-vc2022")

cmake_minimum_required(VERSION 3.5)

SET(TARGET "QTGL")

project(${TARGET} VERSION 0.1 LANGUAGES CXX)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)
                                                                                                                       
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

if(WIN32)
else()
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wno-error=register")
endif()

set(QTGL_GLAPI_PATH "${PROJECT_SOURCE_DIR}/GLAPI")
set(GLAD_FOLDER_INCLUDE_PATH "${PROJECT_SOURCE_DIR}/glad/include")
set(GLAD_FOLDER_SOURCE_PATH  "${PROJECT_SOURCE_DIR}/glad/src")
set(GLM_FOLDER_INCLUDE_PATH  "${PROJECT_SOURCE_DIR}/glm")
set(GLFW_FOLDER_INCLUDE_PATH  "${QTGL_GLAPI_PATH}/glfw")

if(WIN32)
    set(LIBRARY_GLFW_PATH "${PROJECT_SOURCE_DIR}/lib-vc2022")
    LINK_DIRECTORIES("${LIBRARY_GLFW_PATH}")
endif()

include_directories(${QTGL_GLAPI_PATH})
include_directories(${GLAD_FOLDER_INCLUDE_PATH})
include_directories(${GLM_FOLDER_INCLUDE_PATH})
include_directories(${GLFW_FOLDER_INCLUDE_PATH})

file(GLOB GLAPI_HEADERS "${QTGL_GLAPI_PATH}/*.h")
source_group("GLAPI/include" FILES ${GLAPI_HEADERS})

file(GLOB GLAPI_SOURCES "${QTGL_GLAPI_PATH}/*.cpp")
source_group("GLAPI/source" FILES ${GLAPI_SOURCES})

file(GLOB_RECURSE GLAD_INCLUDE "${GLAD_FOLDER_INCLUDE_PATH}/*.*")
source_group("glad/include" FILES ${GLAD_INCLUDE})

file(GLOB GLAD_SOURCE "${GLAD_FOLDER_SOURCE_PATH}/*.*")
source_group("glad/src" FILES ${GLAD_SOURCE})

SET(QTUI_PATH "${PROJECT_SOURCE_DIR}/QTUI")

file(GLOB_RECURSE QTUI_FILES "${QTUI_PATH}/*.*")
source_group("QTUI" FILES ${QTUI_FILES})


set(ALL_SOURCES
        ${GLAPI_HEADERS}
        ${GLAPI_SOURCES}
        ${GLAD_INCLUDE}
        ${GLAD_SOURCE}
        ${QTUI_FILES}
)

ADD_EXECUTABLE(${TARGET} WIN32 ${ALL_SOURCES})

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)


target_link_libraries(${TARGET} PRIVATE Qt${QT_VERSION_MAJOR}::Widgets)

if(WIN32)
    target_link_libraries(${TARGET} PRIVATE debug "${LIBRARY_GLFW_PATH}/glfw3.lib" optimized "${LIBRARY_GLFW_PATH}/glfw3.lib")
    target_link_libraries(${TARGET} PRIVATE debug "${LIBRARY_GLFW_PATH}/glfw3_mt.lib" optimized "${LIBRARY_GLFW_PATH}/glfw3_mt.lib")
    target_link_libraries(${TARGET} PRIVATE debug "${LIBRARY_GLFW_PATH}/glfw3dll.lib" optimized "${LIBRARY_GLFW_PATH}/glfw3dll.lib")
else()
    target_link_libraries(${TARGET} PRIVATE glfw3)
    target_link_libraries(${TARGET} PRIVATE GL)
    target_link_libraries(${TARGET} PRIVATE X11)
    target_link_libraries(${TARGET} PRIVATE m)
    target_link_libraries(${TARGET} PRIVATE pthread)
    target_link_libraries(${TARGET} PRIVATE dl)
endif()

3、第三方库文件

1）glad和glm

glad下载：https://glad.dav1d.de/，下载后得到glad.zip

把glad整个文件夹放置到工程目录下，然后，把src下的glad.c改为glad.cpp。

把glm整个文件夹放置到工程目录下，不需要额外的修改。

2）glfw

glfw下载，Download | GLFW

windows下，需要将编译好的glfw库放置到工程下。如图：

3）整体工程结构如图：

4、QT界面文件QTUI

创建一个QDialog或者QMainWindow，带有.ui文件，可以使用uic指令将其转换为.h文件。

二、OPENGL 简单示例

1、初始化工程

1）初始化glfw，具体解释看：OpenGL学习(一) 绘制一个三角形 - 简书

int DrawApi::initialGlfw()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // glad: load all OpenGL function pointers
    
    return 0;
}

2）创建窗口：

int DrawApi::createWindow(string windowName, OUT GLFWwindow*& window)
{
    // glfw window creation
    // --------------------
    window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, windowName.c_str(), NULL, NULL);
    if (window == NULL)
    {
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        cout << "Failed to initialize GLAD" << endl;
        return -1;
    }

    glViewport(0, 0, 800, 800);

    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);  // 窗体能够根据拉动变化

    return 0;
}

3）顶点着色器

int DrawApi::createVertexShader(OUT GLuint& vertexShader, const char* vertexShaderSource)
{
    //1.初始化着色器
    //创建一个着色器类型
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    //把代码复制进着色器中
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    //编译顶点着色器
    glCompileShader(vertexShader);

    int success;
    char infoLog[512];
    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);

    //判断是否编译成功
    if (!success) {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        cout << "error when vertex compile:" << infoLog << endl;
        return -1;
    }
    return 0;
}

4）片元着色器

int DrawApi::createFragmentShader(OUT GLuint& fragmentShader, const char* fragmentShaderSource)
{
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);

    glCompileShader(fragmentShader);

    int success;
    char infoLog[512];
    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);

    //判断是否编译成功
    if (!success) {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        cout << "error when fragment compile:" << infoLog << endl;
        return -1;
    }
    return 0;
}

5）编译程序

int DrawApi::createProgram(GLuint& vertexShader, GLuint& fragmentShader, OUT GLuint& shaderProgram)
{
    //链接，创建一个程序
    shaderProgram = glCreateProgram();

    //链接上共享库
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    //链接
    glLinkProgram(shaderProgram);

    int success;
    char infoLog[512];
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
        cout << "error when link compile:" << infoLog << endl;
        return -1;
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);
    return 0;
}

6）绘制三角形

int DrawApi::drawTriangles(const vector<vector<float>>& triangelValues)
{
    //1.会先绑定顶点
    //2.绑定缓冲区
    //3.接着把顶点输入到顶点缓冲去中
    //4.把缓冲区的数据传送到着色器中
    //5.输出到屏幕。

    if (initialGlfw() < 0)
        return -1;

    GLFWwindow* window = nullptr;
    if (createWindow("learnOpenGL", window) < 0)
        return -2;

    GLuint vertexShader;
    if (createVertexShader(vertexShader, VERTEX_SHADER) < 0)
        return -3;

    GLuint fragmentShader;
    if (createFragmentShader(fragmentShader, FRAGMENT_SHADER) < 0)
        return -4;

    GLuint shaderProgram;
    if (createProgram(vertexShader, fragmentShader, shaderProgram) < 0)
        return -5;

    if (triangelValues.size() == 0)
        return -6;

    if (triangelValues.size() > 1256)
        return -7;

    float vertices[4096] = {0};

    for (int i = 0; i < triangelValues.size(); i++)
    {
        for (int j = 0; j < 3; j++)
        {
             vertices[3 * i + j] = triangelValues[i][j];
        }
    }

    GLuint VAO;
    // 生成分配VAO
    glGenVertexArrays(1, &VAO);
    // 绑定VAO，注意在core模式，没有绑定VAO，opengl拒绝绘制任何东西
    glBindVertexArray(VAO);

    GLuint VBO;
    // 生成一个VBO缓存对象
    glGenBuffers(1, &VBO);
    // 绑定VBO
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    // 类型为GL_ARRAY_BUFFER 第二第三参数说明要放入缓存的多少，GL_STATIC_DRAW当画面不动的时候推荐使用
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // input
        processInput(window);

        // render
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);


        glUseProgram(shaderProgram);
        //绑定数据
        glBindVertexArray(VAO);
        //绘制一个三角形
        //从0开始，3个
        glDrawArrays(GL_TRIANGLES, 0, triangelValues.size() * 3);

        glBindVertexArray(0);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    glfwTerminate();
    return 0;
}