OpenGL使用纯VBO方式渲染出三角形，要设置兼容格式GLFW_OPENGL_COMPAT_PROFILE。
// 必须使用VAO渲染
//glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// 渲染出纯VBO三角形
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f);\n"
"}\0";
int main()
{
// glfw: initialize and configure
// ------------------------------
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
// 必须使用VAO渲染
//glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// 渲染出纯VBO三角形
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_COMPAT_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
// glfw window creation
// --------------------
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);
// glad: load all OpenGL function pointers
// ---------------------------------------
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
//
float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
// 生成一个VBO对象
unsigned int VBO;
glGenBuffers(1, &VBO);
// 生成一个VAO
//unsigned int VAO;
//glGenVertexArrays(1, &VAO);
//glBindVertexArray(VAO);
// 绑定到数组缓冲
glBindBuffer(GL_ARRAY_BUFFER, VBO);
// 复制顶点数据到缓冲内存
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
printf("glBufferData sizeof(vertices)=%d\n", sizeof(vertices));
// sizeof(vertices)=36
// 设置顶点属性指针，并启用
//layout(location = 0 aPosition
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
//location = 0
glEnableVertexAttribArray(0); //顶点坐标
// 解绑
// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0);
/*三角形的位置数据不会改变，每次渲染调用时都保持原样，所以它的使用类型最好是GL_STATIC_DRAW。
如果，比如说一个缓冲中的数据将频繁被改变，
那么使用的类型就是GL_DYNAMIC_DRAW或GL_STREAM_DRAW，
这样就能确保显卡把数据放在能够高速写入的内存部分。*/
// 创建顶点着色器，
unsigned int vertexShader;
vertexShader = glCreateShader(GL_VERTEX_SHADER);
// 附加上着色器源代码
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
// 编译着色器
glCompileShader(vertexShader);
// 检测是否编译成功
int success = 0;
char infoLog[512] = { 0 };
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(vertexShader, sizeof(infoLog), NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
else
{
std::cout << "SHADER::VERTEX::COMPILATION SUCCESS!";
}
// 创建片段着色器
unsigned int fragmentShader;
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
// 附加上片段着色器源代码
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
// 编译
glCompileShader(fragmentShader);
// 判断编译结果
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, sizeof(infoLog), NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
else
{
std::cout << "SHADER::FRAGMENT::COMPILATION SUCCESS!" << std::endl;
}
// 创建着色器程序
unsigned int shaderProgram;
shaderProgram = glCreateProgram();
// 链接之前编译的着色器
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// 判断着色器程序链接结果
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::COMPILATION_FAILED\n" << infoLog << std::endl;
}
else
{
std::cout << "SHADER::LinkProgram SUCCESS!" << std::endl;
}
// 删除之前链接过的对象
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
//glBindVertexArray(0);
// render loop
// -----------
while (!glfwWindowShouldClose(window))
{
// input
// -----
processInput(window);
// render
// ------
glClearColor(0.1f, 0.3f, 0.2f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// 激活程序对象
glUseProgram(shaderProgram);
//glBindVertexArray(VAO);
//glBindVertexArray(VAO);
//glBindBuffer(GL_ARRAY_BUFFER, VBO);
glDrawArrays(GL_TRIANGLES, 0, 3);
//glDrawElements(GL_TRIANGLES, 1, GL_UNSIGNED_SHORT, 0);
// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
// -------------------------------------------------------------------------------
glfwSwapBuffers(window);
glfwPollEvents();
}
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
if(glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
//glViewport(0, 0, width, height);
glViewport(0, 0, 100, 100);
}