OpenGL和Imgui整合入门1

辛琪

2022-02-15 2022-02-15 约 1606 字预计阅读 4 分钟次阅读

OpenGL入门

先上效果图

环境配置

OpenGL有很多开源库，如常见的glad，glfw，glut等等，这里简述一下他们的区别：

glut是一个年代比较久远的窗口管理库，现在已经被glfw替代，不建议使用
glfw，轻量级gl库，针对OpenGL的C语言库，提供最低限度的接口，允许用户创建OpenGL上下文，定义窗口参数，处理用户输入等
glew，函数加载库，年代久远，不建议使用
glad，glew的较先进替代品

所以现在一般采用glad和glfw进行OpenGL开发，两个库的下载链接如下：

GLFW:http://www.glfw.org/download.html

glad：https://glad.dav1d.de/

具体环境配置教程网上有很多，这里采用了VS进行配置

记得引入glad.c文件

配置完毕后，在网上找一段测试代码，看看配置是否有问题

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#include <glad/glad.h>
#include <gl/glfw3.h>
#include <iostream>
using namespace std;

void framebuffer_size_callback(GLFWwindow* window, int width, int height);

void processInput(GLFWwindow* window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

//创建main函数，实例化glfw窗口
int main()
{
    //实例化glfw窗口，并告诉glfw使用的opengl版本：major 3，minor 3（3.3）
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

    //创建窗口对象
    GLFWwindow* window = glfwCreateWindow(800, 600, "OpenGLTest", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

    //初始化GLAD
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    glViewport(0, 0, 800, 600);

    //注册回调函数，窗口大小改变时候调用
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    //开始渲染循环
    while (!glfwWindowShouldClose(window))
    {
        processInput(window);//输入检测

        glfwSwapBuffers(window);//双缓冲绘制
        glfwPollEvents();
    }
    glfwTerminate();//资源释放

    return 0;
}

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

这里注意，glad库必须在glfw库前包含否则会报错，编译后无法运行的同学记得查看自己的项目结构是否为32位(x86)

learn opengl官网上的注意事项

请确认是在包含GLFW的头文件之前包含了GLAD的头文件。GLAD的头文件包含了正确的OpenGL头文件（例如GL/gl.h），所以需要在其它依赖于OpenGL的头文件之前包含GLAD。

界面库采用ImGui，比较美观，使用也挺便捷

ImGui：https://github.com/ocornut/imgui

下载压缩包后直接解压到项目里然后包含就行

根据learn-opengl网站的教程进行一个简单的编写

部分代码：

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//ImGui部分
    {

            static int counter = 0;

            ImGui::Begin("Edit");                          // Create a window called "Hello, world!" and append into it.

            ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
            ImGui::Checkbox("Another Window", &show_another_window);

            ImGui::ColorEdit3("color", (float*)&color);            // Edit 1 float using a slider from 0.0f to 1.0f
            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

            if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                counter++;
            ImGui::SameLine();
            ImGui::Text("counter = %d", counter);

            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
            ImGui::End();
        }
ImGui::Render();
......
//绘制部分
    // 更新uniform颜色
        ourShader.setVec4("newcolor", color.x, color.y, color.z, 1);
        //std::cout << color.x << " " << color.y << " " << color.z << " " << color.w << endl;
        ourShader.use();
        glDrawArrays(GL_TRIANGLES, 0, 3);


        glfwSwapBuffers(window);//双缓冲绘制
//从文件读取顶点着色器和片元着色器
Shader(const char* vertexPath, const char* fragmentPath, const char* geometryPath = nullptr)
    {
        // 1. retrieve the vertex/fragment source code from filePath
        std::string vertexCode;
        std::string fragmentCode;
        std::string geometryCode;
        std::ifstream vShaderFile;
        std::ifstream fShaderFile;
        std::ifstream gShaderFile;
        // ensure ifstream objects can throw exceptions:
        vShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
        fShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
        gShaderFile.exceptions(std::ifstream::failbit | std::ifstream::badbit);
        try
        {
            // open files
            vShaderFile.open(vertexPath);
            fShaderFile.open(fragmentPath);
            std::stringstream vShaderStream, fShaderStream;
            // read file's buffer contents into streams
            vShaderStream << vShaderFile.rdbuf();
            fShaderStream << fShaderFile.rdbuf();
            // close file handlers
            vShaderFile.close();
            fShaderFile.close();
            // convert stream into string
            vertexCode = vShaderStream.str();
            fragmentCode = fShaderStream.str();
            // if geometry shader path is present, also load a geometry shader
            if (geometryPath != nullptr)
            {
                gShaderFile.open(geometryPath);
                std::stringstream gShaderStream;
                gShaderStream << gShaderFile.rdbuf();
                gShaderFile.close();
                geometryCode = gShaderStream.str();
            }
        }
        catch (std::ifstream::failure& e)
        {
            std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
        }
        const char* vShaderCode = vertexCode.c_str();
        const char* fShaderCode = fragmentCode.c_str();
        // 2. compile shaders
        unsigned int vertex, fragment;
        // vertex shader
        vertex = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vertex, 1, &vShaderCode, NULL);
        glCompileShader(vertex);
        checkCompileErrors(vertex, "VERTEX");
        // fragment Shader
        fragment = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fragment, 1, &fShaderCode, NULL);
        glCompileShader(fragment);
        checkCompileErrors(fragment, "FRAGMENT");
        // if geometry shader is given, compile geometry shader
        unsigned int geometry;
        if (geometryPath != nullptr)
        {
            const char* gShaderCode = geometryCode.c_str();
            geometry = glCreateShader(GL_GEOMETRY_SHADER);
            glShaderSource(geometry, 1, &gShaderCode, NULL);
            glCompileShader(geometry);
            checkCompileErrors(geometry, "GEOMETRY");
        }
        // shader Program
        ID = glCreateProgram();
        glAttachShader(ID, vertex);
        glAttachShader(ID, fragment);
        if (geometryPath != nullptr)
            glAttachShader(ID, geometry);
        glLinkProgram(ID);
        checkCompileErrors(ID, "PROGRAM");
        // delete the shaders as they're linked into our program now and no longer necessery
        glDeleteShader(vertex);
        glDeleteShader(fragment);
        if (geometryPath != nullptr)
            glDeleteShader(geometry);

    }
//SHADER_H头文件部分
 void setVec4(const std::string& name, float x, float y, float z, float w)
    {
        glUniform4f(glGetUniformLocation(ID, name.c_str()), x, y, z, w);
    }

后续会具体说明ImGui的使用流程等

目录

OpenGL和Imgui整合入门1

环境配置