OpenGL -- 你好三角形

  1 #include <glad/glad.h>
  2 #include <GLFW/glfw3.h>
  3 
  4 #include <iostream>
  5 
  6 void framebuffer_size_callback(GLFWwindow* window, int width, int height);
  7 void processInput(GLFWwindow* window);
  8 const char* vertexShaderSource = "#version 330 core\n"
  9 "layout (location = 0) in vec3 aPos;\n"
 10 "void main()\n"
 11 "{\n"
 12 "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
 13 "}\0";
 14 const char* fragmentShaderSource = "#version 330 core\n"
 15 "out vec4 FragColor;\n"
 16 "void main()\n"
 17 "{\n"
 18 "   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
 19 "}\n\0";
 20 int main()
 21 {
 22     glfwInit();
 23     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
 24     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
 25     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 26 
 27     GLFWwindow* window = glfwCreateWindow(2000, 2000, "LearnOpenGL", NULL, NULL);
 28     if (window == NULL)
 29     {
 30         std::cout << "Failed to create GLFW window" << std::endl;
 31         glfwTerminate();
 32         return -1;
 33     }
 34     glfwMakeContextCurrent(window);
 35     glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
 36 
 37     if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
 38     {
 39         std::cout << "Failed to initialize GLAD" << std::endl;
 40         return -1;
 41     }
 42 
 43     
 44 
 45     unsigned int vertexShader;
 46     vertexShader = glCreateShader(GL_VERTEX_SHADER);
 47     glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
 48     glCompileShader(vertexShader);
 49     int  success;
 50     char infoLog[512];
 51     glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
 52     if (!success)
 53     {
 54         glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
 55         std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
 56     }
 57 
 58 
 59     unsigned int fragmentShader;
 60     fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
 61     glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
 62     glCompileShader(fragmentShader);
 63 
 64 
 65     unsigned int shaderProgram;
 66     shaderProgram = glCreateProgram();
 67     glAttachShader(shaderProgram, vertexShader);
 68     glAttachShader(shaderProgram, fragmentShader);
 69     glLinkProgram(shaderProgram);
 70 
 71     glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
 72     if (!success) {
 73         glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
 74         std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
 75     }
 76 
 77     glUseProgram(shaderProgram);
 78     glDeleteShader(vertexShader);
 79     glDeleteShader(fragmentShader);
 80 
 81     float vertices[] = {
 82      -0.5f, -0.5f, 0.0f, 
 83      0.0f, -0.5f, 0.0f,  
 84      -0.25f, 0.5f, 0.0f,
 85      0.0f, -0.5f, 0.0f,
 86      0.5f, -0.5f, 0.0f,
 87      0.25f, 0.5f, 0.0f
 88     };
 89 
 90     unsigned int indices[] = { // 注意索引从0开始! 
 91         0, 1, 2, // 第一个三角形
 92         3, 4, 5  // 第二个三角形
 93     };
 94     unsigned int VBO, VAO, EBO;
 95     glGenBuffers(1, &EBO);
 96     glGenVertexArrays(1, &VAO);
 97     glGenBuffers(1, &VBO);//生成
 98 
 99     glBindVertexArray(VAO);
100 
101     glBindBuffer(GL_ARRAY_BUFFER, VBO);
102     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
103 
104     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);//把新创建的缓冲绑定到目标上
105     glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
106     //一个专门用来把用户定义的数据复制到当前绑定缓冲的函数
107 
108 
109     glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);//告诉OpenGL该如何解析顶点数据
110     //每个顶点属性从一个VBO管理的内存中获得它的数据，而具体是从哪个VBO（程序中可以有多个VBO）获取
111     //则是通过在调用glVertexAttribPointer时绑定到GL_ARRAY_BUFFER的VBO决定的。
112     glEnableVertexAttribArray(0);//vertex attribute location as its argument.
113     //vertex attributes are disabled by default.
114 
115     glBindBuffer(GL_ARRAY_BUFFER, 0);//参数0，好像是解绑的意思
116     glBindVertexArray(0);
117     //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
118     while (!glfwWindowShouldClose(window))
119     {
120         processInput(window);
121 
122         glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
123         glClear(GL_COLOR_BUFFER_BIT);
124 
125         glUseProgram(shaderProgram);
126         glBindVertexArray(VAO);
127         glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
128         glBindVertexArray(0);
129 
130         glfwSwapBuffers(window);
131         glfwPollEvents();
132     }
133 
134     glDeleteVertexArrays(1, &VAO);
135     glDeleteBuffers(1, &VBO);
136     glDeleteBuffers(1, &EBO);
137 
138     glfwTerminate();
139  
140     return 0;
141 }
142 
143 
144 void framebuffer_size_callback(GLFWwindow* window, int width, int height)
145 {
146     glViewport(0, 0, width, height);
147 }
148 
149 void processInput(GLFWwindow* window)
150 {
151     if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
152         glfwSetWindowShouldClose(window, true);
153 }