OpenGL教程2_创建窗口

预备知识

OpenGL:
开放图形库，或者说是一个图形标准。
GLFW：
Graphics Library For Windows 目的是实现 创建，管理窗口，增加交互性（鼠标，键盘，和其他设备），和其他是操作系统打交道的事情，由GLUT、FreeGLUT发展而来
GLAD
GL ADdress,获取OpenGL拓展函数的地址，并绑定到对应的函数指针上，方便对函数的调用
GLSL
OpenGL的着色器语言，绘制图像纹理时会用到

1、导入相关的库

GLFW用于窗口的绘制和交互，GLAD用于加载GLFW函数指针地址

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>

2、初使化glfw

glfwInit初使化，版本为3.3，模式为核心模式，Mac额外配置

    glfwInit(); 
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); 
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); 
#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

3、创建窗口

GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
    std::cout << "Failed to create GLFW window" << std::endl;
    glfwTerminate();
    return -1;
}
glfwMakeContextCurrent(window);

4、初使化glad

加载GLFW函数指针地址

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

5、设置视图

framebuffer_size_callback是窗口大小变化时的回调函数,随时修改窗口显示

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

6、持续渲染，以免渲染一次后就退出

    while (!glfwWindowShouldClose(window))
    {
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

7、设置背景颜色

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

附加功能

点击esc按键，退出界面

processInput(window);

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

释放/删除之前的分配的所有资源

glfwTerminate();

完整代码

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>

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

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }
    while (!glfwWindowShouldClose(window))
    {
        processInput(window);

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

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glfwTerminate();
    return 0;
}

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

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