画一个正方形

其实，画正方形就是画两个三角形，用四个顶点以及使用索引来实现
完整代码在Square项目的Application.cpp里
先贴上窗口初始化代码

void BaseInit()
{glfwInit();//初始化glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//配置GLFWglfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);//配置GLFWglfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//glfwWindowHint(GLFW_RESIZABLE, GL_TRUE);float screenWidth = 800.0f;float screenHeight = 600.0f;//创建窗口glWindow = glfwCreateWindow(screenWidth, screenHeight, "LearnOpenGL", nullptr, nullptr);if (glWindow == nullptr){cout << "Failed to create GLFW window" << endl;glfwTerminate();return;}glfwMakeContextCurrent(glWindow);if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){std::cout << "Failed to initialize GLAD" << std::endl;return;}

画一个普通的正方形

void NormalSquare()
{float vertices[] = {//     ---- 位置 ----0.5f,  0.5f, 0.0f,  // 右上0.5f, -0.5f, 0.0f,  // 右下-0.5f, -0.5f, 0.0f,  // 左下-0.5f,  0.5f, 0.0f,  // 左上};//索引unsigned int indices[] = {0,1,3,1,2,3};//编译着色器Shader ourShader("vertex_1.vs", "fragment_1.fs");ourShader.use();//glUseProgram(shaderProgram);unsigned int VAO;//顶点数组glGenVertexArrays(1, &VAO);glBindVertexArray(VAO);//绑定顶点数组缓存unsigned int VBO;glGenBuffers(1, &VBO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//绑定索引缓存unsigned int EBO;glGenBuffers(1, &EBO);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);// 位置属性glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);while (!glfwWindowShouldClose(glWindow)){glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);//drawglBindVertexArray(VAO);glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);glBindVertexArray(0);glfwPollEvents();glfwSwapBuffers(glWindow);}glDeleteVertexArrays(1, &VAO);glDeleteBuffers(1, &VBO);glDeleteBuffers(1, &EBO);glfwTerminate();
}

最终效果

画一个彩色的正方形

和上一个笔记里画彩色三角形的逻辑一样，在顶点属性后面加上颜色属性，设置数据访问指针的属性，记得顶点着色器要加上颜色的输入(步长和相位)

//彩色正方形
void ColourfulSquare()
{float vertices[] = {//     ---- 位置 ----       ---- 颜色 ---- 0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,  // 右上0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,  // 右下-0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,  // 左下-0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,  // 左上};//索引unsigned int indices[] = {0,1,3,1,2,3};//编译着色器Shader ourShader("vertex_4.vs", "fragment_4.fs");ourShader.use();//glUseProgram(shaderProgram);unsigned int VAO;//顶点数组glGenVertexArrays(1, &VAO);glBindVertexArray(VAO);//绑定顶点数组缓存unsigned int VBO;glGenBuffers(1, &VBO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//绑定索引缓存unsigned int EBO;glGenBuffers(1, &EBO);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);// 位置属性glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);// 颜色属性glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float))); //最后一个参数是数据的起点glEnableVertexAttribArray(1);while (!glfwWindowShouldClose(glWindow)){glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);//drawglBindVertexArray(VAO);glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);glBindVertexArray(0);glfwPollEvents();glfwSwapBuffers(glWindow);}glDeleteVertexArrays(1, &VAO);glDeleteBuffers(1, &VBO);glDeleteBuffers(1, &EBO);glfwTerminate();
}

最终效果

可以试试线框模式，在while之前加上
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
效果图