OpenGL_6:用两个VBO和VAO分别画2个三角形

#include <stdio.h>
#include <GLAD/glad.h>
#include <GLFW/glfw3.h>

const char *vertexShaderSource =
"#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main(){\n"
"gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0f);\n"
"}\n\0";

const char *fragmentShaderSource =
"#version 330 core\n"
"out vec4 FragColor;\n"
"void main(){\n"
"FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";

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

int main() {

glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

GLFWwindow *glfWwindow = glfwCreateWindow(800, 600, "Square", NULL, NULL);
if (NULL == glfWwindow){
printf("Failed to create window \n");
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(glfWwindow);
glfwSetFramebufferSizeCallback(glfWwindow, framebuffer_size_callback);

if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){
printf("Failed to initialize GLAD\n");
}

unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);

int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success){
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
printf("Failed to compile vertexShader:%s
4000
\n", infoLog);
}

unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);

glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success){
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
printf("Failed to compile fragmentShader:%s \n", infoLog);
}

unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);

glGetShaderiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success){
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
printf("Failed to link shaderProgram:%s \n", infoLog);
}

glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);

float vertices_1[] = {
// first triangle
-0.9f, -0.5f, 0.0f,  // left
-0.0f, -0.5f, 0.0f,  // right
-0.45f, 0.5f, 0.0f  // top
};

float vertices_2[] = {
// second triangle
0.0f, -0.5f, 0.0f,  // left
0.9f, -0.5f, 0.0f,  // right
0.45f, 0.5f, 0.0f   // top
};

unsigned int VBO[2], VAO[2];
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);

glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices_1), vertices_1, GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
//    glBindVertexArray(0);  //no need to unbind at all as we directly bind a different VAO the next few lines

//    glBindBuffer(GL_ARRAY_BUFFER, 0);

glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices_2), vertices_2, GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// glBindVertexArray(0); // not really necessary as well, but beware of calls that could affect VAOs while this one is bound (like binding element buffer objects, or enabling/disabling vertex attributes)

//    glBindBuffer(GL_ARRAY_BUFFER, 0);

/**
* 当目标是GL_ELEMENT_ARRAY_BUFFER的时候，VAO会储存glBindBuffer的函数调用。
* 这也意味着它也会储存解绑调用，所以确保你没有在解绑VAO之前解绑索引数组缓冲，
* 否则它就没有这个EBO配置了。
* */
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

while (!glfwWindowShouldClose(glfWwindow)){

processInput(glfWwindow);

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

glUseProgram(shaderProgram);

glBindVertexArray(VAO[0]);
glDrawArrays(GL_TRIANGLES, 0, 3);

glBindVertexArray(VAO[1]);
glDrawArrays(GL_TRIANGLES, 0, 3);

//        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

glfwSwapBuffers(glfWwindow);
glfwPollEvents();
}

glDeleteVertexArrays(2, VAO);
glDeleteBuffers(2, VBO);

glfwTerminate();
return 0;
}

void processInput(GLFWwindow *glfWwindow){
if (glfwGetKey(glfWwindow, GLFW_KEY_ESCAPE))
glfwSetWindowShouldClose(glfWwindow, GLFW_TRUE);
}

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