CODEWITHSUNDEEP
c++openglglut
Nick
Nick

Reputation: 10499

Basic triangle drawing with OpenGL

I have the following code

#include <iostream>
using namespace std;

#include <GL\glew.h>
#include <GL\freeglut.h>


#define BUFFER_OFFSET(a) ((void*)(a))


enum eAttributesIDs
{
    Position = 0,
    Color = 1
};


void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glFlush();
}


void init()
{
    GLfloat vertices[] = 
    {
        0.f, 1.f,
        -1.f, -1.f,
        1.f, -1.f
    };

    GLuint bufferId;
    glGenBuffers(1, &bufferId);
    glBindBuffer(GL_ARRAY_BUFFER, bufferId);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glEnableVertexAttribArray(Position);
    glVertexAttribPointer(Position, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0));

    glClearColor(0, 1, 1, 1);
}


int main(int argc, char** argv)
{
    // configure and open window via glut
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA);
    glutInitWindowSize(640, 480);
    glutInitContextVersion(4, 3);
    glutInitContextProfile(GLUT_CORE_PROFILE);
    glutCreateWindow(argv[0]);

    if (glewInit()) 
    {
        cerr << "Unable to initialize GLEW" << endl;
        exit(EXIT_FAILURE);
    }

    init();

    glutDisplayFunc(display);
    glutMainLoop();

    return 0;
}

But I can't figure out why, even if it compiles and it runs changing the background color of the window, no triangle appears on the screen.

Upvotes: 0

Views: 803

Answers (1)

Bartvbl
Bartvbl

Reputation: 2928

I think you're missing a shader program & VAO. It's mandatory to use them when using a Core OpenGL context.

Upvotes: 3

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