openGL handle VAO, VBO, and EBO creation inside another class

Question

I created a simple program that draw a square to the screen.

int main()
{

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

    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);

    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    gladLoadGLLoader((GLADloadproc)glfwGetProcAddress));

    Shader* shader = new Shader("vertexShader.glsl", "fragmentShader.glsl");

    float vertices[] = {
         0.5f,  0.5f, 0.0f,  // top right
         0.5f, -0.5f, 0.0f,  // bottom right
        -0.5f, -0.5f, 0.0f,  // bottom left
        -0.5f,  0.5f, 0.0f   // top left 
    };
    unsigned int indices[] = {  // note that we start from 0!
        0, 1, 3,  // first Triangle
        1, 2, 3   // second Triangle
    };

    unsigned int VBO, VAO, EBO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

Then I tried to move the part that handles the vertices, indices, and the creation of the VAO, VBO, and EBO, to another class named Cube.

Cube::Cube()
{

    // type GLfloat
    vertices = {
          0.5f,  0.5f, 0.0f,  // top right
          0.5f, -0.5f, 0.0f,  // bottom right
         -0.5f, -0.5f, 0.0f,  // bottom left
         -0.5f,  0.5f, 0.0f   // top left 
    };

    // type GLfloat
    indices = {  // note that we start from 0!
        0, 1, 3,  // first Triangle
        1, 2, 3   // second Triangle
    };

    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    glGenBuffers(1, &EBO);

    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, vertices.size(), &vertices[0], GL_STATIC_DRAW);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size(), &indices[0], GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

but when I tried to use the VAO of the Cube class in order to draw the square, nothing drew to the screen.

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);

    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }

    Shader* shader = new Shader("vertexShader.glsl", "fragmentShader.glsl");
    Cube* cube = new Cube();

    while (!glfwWindowShouldClose(window))
    {
        processInput(window);

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

        glUseProgram(shader->program);
        glBindVertexArray(cube->VAO);
  
        glDrawElements(GL_TRIANGLES, cube->indices.size(), GL_FLOAT, 0);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &cube->VAO);
    glDeleteBuffers(1, &cube->VBO);
    glDeleteBuffers(1, &cube->EBO);
    glDeleteProgram(shader->program);

    glfwTerminate();
    return 0;
}

I didn't change anything else besides that so I have no idea what is the problem

Answer 1

See glBufferData . The buffer size must be specified in bytes:

glBufferData(GL_ARRAY_BUFFER, vertices.size(), &vertices[0], GL_STATIC_DRAW);

glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(GLfloat),
             vertices.data(), GL_STATIC_DRAW);

glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size(), &indices[0], GL_STATIC_DRAW);

glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(GLuint),
             indices.data(), GL_STATIC_DRAW);

See glDrawElements . The type of the indices must be integral, eg GLuint / GL_UNSIGNED_INT .

glDrawElements(GL_TRIANGLES, cube->indices.size(), GL_FLOAT, 0);

glDrawElements(GL_TRIANGLES, cube->indices.size(), GL_UNSIGNED_INT, 0);