OpenGL cannot draw with glVertexAttrib in core profile - c++

Question

I want to use OpenGL 3.1.
I'm using a Macbook Pro with 2 graphic cards: NVIDIA GeForce GT 650M 1024 MB, and Intel HD Graphics 4000 1536 MB. They both support up to OpenGL 4.1.
Previously i was able to draw a triangle however, my program was using version 2.1. Therefore I added: SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);. However, now the triangle is no longer drawn.
#include <string>
#include <iostream>
#include <SDL2/SDL.h>
#define GL3_PROTOTYPES 1
#include "../include/GL3/gl3.h"
int main(int argc, const char *argv[]) {
// Initialize the SDL
if(SDL_Init(SDL_INIT_VIDEO) < 0) {
std::cout << "Failed to initialize the SDL: " << SDL_GetError() << std::endl;
SDL_Quit();
return -1;
}
// Configure the SDL to use OpenGL 3.1
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 1);
// ======= HERE =======
SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
// ====================
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
SDL_Window* window = SDL_CreateWindow("Triangle Test", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 800, 600, SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL);
if (window == 0) {
std::cout << "Error when creating the window: " << SDL_GetError() << std::endl;
SDL_Quit();
return -1;
}
// Create the OpenGL context
SDL_GLContext contextOpenGL = SDL_GL_CreateContext(window);
// Initialization may fail
if (contextOpenGL == 0) {
std::cout << SDL_GetError() << std::endl;
SDL_DestroyWindow(window);
SDL_Quit();
return -1;
}
SDL_Event events;
bool end = false;
// Define the vertices of our triangle
static const GLfloat vertices[] = {0.0, 1.0, // left point
-0.5, 0.0, // right point
0.5, 0.0}; // upper point
const int TRIANGLE_IDX = 0;
while(!end) {
SDL_WaitEvent(&events);
if(events.window.event == SDL_WINDOWEVENT_CLOSE) {
end = true;
}
// Clear the screen
glClear(GL_COLOR_BUFFER_BIT);
// Send vertices to OpenGL
glVertexAttribPointer(TRIANGLE_IDX, 2, GL_FLOAT, GL_FALSE, 0, vertices);
// Activate our vertex array
glEnableVertexAttribArray(TRIANGLE_IDX);
// Draw the points passed previously
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(TRIANGLE_IDX);
// Refresh the screen
SDL_GL_SwapWindow(window);
}
return 0;
}
I tried to first use glGenBuffers, glBindBuffer and glBufferData but i could not manage to make it work.

Answer 1

The Fixed Function Pipeline has been removed from core OpenGL 3.1 and above.
You will have to use shaders instead. This site has a nice example of how to use them.