#include <stdlib.h>
#include <GL/glut.h>
GLfloat vert1X = 0.25, vert1Y = 0.25, vert2X = 0.75, vert2Y = 0.25,
        vert3X = 0.75, vert3Y = 0.75;

void display(void)
{
  /* clear all pixels */

  glClear(GL_COLOR_BUFFER_BIT);

  /* draw red  polygon (triangle)*/ 
  glColor3f(1.0, 0.0, 0.0);

  glBegin(GL_POLYGON);
  glVertex2f(vert1X, vert1Y);
  glVertex2f(vert2X, vert2Y);
  glVertex2f(vert3X, vert3Y);
 
  glEnd();

  /* dont wait
   * start processing buffered OpenGL routines
   */
  glFlush();
}

void init(int arg, char* arg_vec[])
{
   /* select clearing (background) color   */
   glClearColor(0.0, 0.0, 0.0, 0.0);
   vert1X =  atof (arg_vec[1]);
   vert1Y = atof (arg_vec[2]);
   vert2X =  atof (arg_vec[3]);
   vert2Y =  atof (arg_vec[4]);
   vert3X =  atof (arg_vec[5]);
   vert3Y =  atof (arg_vec[6]);
   
   /* initialize viewing values */
   glMatrixMode(GL_PROJECTION); 
   glLoadIdentity();
   glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
 }

int main(int argc, char* argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
  glutInitWindowSize(450, 450);
  glutInitWindowPosition(0,0);
  glutCreateWindow("Drawing Objects");
  init(argc, argv);
  glutDisplayFunc(display);
  glutMainLoop();
  return 0;
}