如何在两个阶段编写OpenGL片段着色器？

// 创建片段着色器对象
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

// 加载着色器代码
const char* shaderCode = R"(
    #version 330 core
    in vec3 fragmentColor;
    out vec4 fragColor;
    void main()
    {
        fragColor = vec4(fragmentColor, 1.0);
    }
)";
glShaderSource(fragmentShader, 1, &shaderCode, nullptr);

// 编译着色器代码
glCompileShader(fragmentShader);

// 检查编译错误
GLint success;
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
    GLchar infoLog[512];
    glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
    std::cout << "Error compiling fragment shader: " << infoLog << std::endl;
}

// 删除着色器对象
glDeleteShader(fragmentShader);

// 创建着色器程序对象
GLuint shaderProgram = glCreateProgram();

// 将片段着色器附加到程序对象上
glAttachShader(shaderProgram, fragmentShader);

// 链接着色器程序
glLinkProgram(shaderProgram);

// 检查链接错误
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success)
{
    GLchar infoLog[512];
    glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
    std::cout << "Error linking shader program: " << infoLog << std::endl;
}

// 使用着色器程序
glUseProgram(shaderProgram);

// 在渲染循环中使用着色器程序进行渲染
while (!glfwWindowShouldClose(window))
{
    // 渲染代码...
    // ...

    // 交换缓冲区并检查事件
    glfwSwapBuffers(window);
    glfwPollEvents();
}

// 删除着色器程序对象
glDeleteProgram(shaderProgram);