Um Hello World em OpenGL usando C e GLUT.

hw-glut.c

#include <GL/freeglut.h>

void desenhaMinhaCena(void)
{
    glClearColor(1, 1, 1, 1);
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_TRIANGLE_FAN);
        glVertex3f(-0.5, -0.5, 0.0);
        glVertex3f( 0.5, -0.5, 0.0);
        glVertex3f( 0.5,  0.5, 0.0);
        glVertex3f(-0.5,  0.5, 0.0);
    glEnd();
    glFlush();
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutInitWindowSize(500, 500);
    glutCreateWindow("Hello World");
    glutDisplayFunc(desenhaMinhaCena);
    glutMainLoop();
    return 0;
}