OpenGL - can't use glew 3.0 [closed]

Question

I've been trying to follow a tutorial of glew, but i can't run this glGenVertexArrays, it always leads to a memmory access violation!...

I tried glExperimental = GL_TRUE too, also updated my video card driver 2 times, but it doesn't run.

Btw, there's my code (to TRY to generate a simple triangle):

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;

#include <glew.h>
#include <glfw.h>
#include <glm/glm.hpp>
using namespace glm;

#define GLFW_DLL
//#pragma comment(linker,  "/SUBSYSTEM:WINDOWS")
//#pragma comment(linker, "/ENTRY:mainCRTStartup")

int main()
{

    //glewExperimental = GL_TRUE;

    if(!glfwInit())
    {
        cout << "Failed to load graphics... " << endl; 
        return -1;
    }



    GLuint VertexArrayID;
    glGenVertexArrays(1, &VertexArrayID);
    glBindVertexArray(VertexArrayID);


    static const GLfloat g_vertex_buffer_data[] = 
    {
        -1.0f, -1.0f,  0.0f,
         1.0f, -1.0f,  0.0f,
         0.0f,  1.0f,  0.0f,
    };

    GLuint vertexbuffer;
    glGenBuffers(1, &vertexbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);


    glfwOpenWindowHint(GLFW_FSAA_SAMPLES, 4);
    glfwOpenWindowHint(GLFW_VERSION_MAJOR, 3);
    glfwOpenWindowHint(GLFW_VERSION_MINOR, 1);
    //glfwOpenWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwOpenWindowHint(GLFW_OPENGL_PROFILE, 0);

    if(!glfwOpenWindow(1024, 768, 0, 0, 0, 0, 32, 0, GLFW_WINDOW))
    {
        cout << "Failed to open window";
        glfwTerminate();
        return -2;
    }

    glfwSetWindowTitle("IfUSeeingThisMsgTheShitWorked");

    glfwEnable(GLFW_STICKY_KEYS);

    //Main loop
    do
    {
        cout << "happaned";
        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
        glVertexAttribPointer(0,3, GL_FLOAT, GL_FALSE, 0, (void*) 0);

        glDrawArrays(GL_TRIANGLES, 0, 3);
        glDisableVertexAttribArray(0);

        glfwSwapBuffers();

    }while(glfwGetKey(GLFW_KEY_ESC) != GLFW_PRESS && glfwGetWindowParam(GLFW_OPENED));



    return 0;
}

Also, I want to point out that this function doesn't work:

glfwOpenWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

so I had to change it to:

glfwOpenWindowHint(GLFW_OPENGL_PROFILE, 0);

Does it have anything to do with my error? hm.

I'm posting it here, just to make sure that there's no other thing I can do, other than buy a new video card. I really want to use the modern OpenGL, it is pointless to learn the old one.

Answer 1

You're not actually calling glewInit in your code, so you're not even loading the GL entry points. You should add a call to glewInit after your glfwInit call, like so:

if(!glfwInit())
{
    cout << "Failed to load graphics... " << endl; 
    return -1;
}

if (glewInit () != GLEW_NO_ERROR)
{
    cout << "Failed to initialize GLEW... " << endl; 
    return -1;
}

// check for required GL_VERSION and extensions here and error out if requirements not met

// and everything else should follow the same as before from here...
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);

Answer 2

You're apparently not using Glew at all: you don't initialise the library. It looks like you haven’t even read the first sentence of the first paragraph of the GLEW documentation.

Another thing you do before even creating the OpenGL context is create a vertex buffer. That cannot work either: OpenGL doesn’t exist until you create an OpenGL context.

This is the order in which you need to do things:

• Create an OpenGL context (using glfw)
• Initialise GLEW
• Use OpenGL functions