Coding Bus dalam Opengl

#include <GL/glut.h>
#include <math.h>

void
display(void)
{
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_POLYGON);
  glColor3f(1.0, 0.0, 0.0);
    glVertex2d(-0.9,-0.5);
    glVertex2d(0.9,-0.5);
    glVertex2d(0.9, 0.5);
    glVertex2d(-0.7, 0.5);
    glVertex2d(-0.9, 0.2);
  glEnd();
 
  glBegin(GL_POLYGON);
  glColor3f(1.0, 0.0, 1.0);
    glVertex2d(-0.8,-0.4);
    glVertex2d(-0.5,-0.4);
    glVertex2d(-0.5, 0.4);
    glVertex2d(-0.7, 0.4);
    glVertex2d(-0.8, 0.2);
  glEnd();
 
  glBegin(GL_POLYGON);
  glColor3f(0.75, 0.75, 0.75);
    glVertex2d(-0.4, 0.0);
    glVertex2d(-0.1, 0.0);
    glVertex2d(-0.1, 0.4);
    glVertex2d(-0.4, 0.4);
  glEnd();
 
  glBegin(GL_POLYGON);
  glColor3f(0.75, 0.75, 0.75);
    glVertex2d(0.0, 0.1);
    glVertex2d(0.4, 0.1);
    glVertex2d(0.4, 0.4);
    glVertex2d(0.0, 0.4);
  glEnd();
 
glBegin(GL_POLYGON);
  glColor3f(0.75, 0.75, 0.75);
    glVertex2d(0.5, 0.0);
    glVertex2d(0.8, 0.0);
    glVertex2d(0.8, 0.4);
    glVertex2d(0.5, 0.4);
     glEnd();
  glFlush();  /* Single buffered, so needs a flush. */
}

int
main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutCreateWindow("BUS");
  glutDisplayFunc(display);
  glutMainLoop();
  return 0;
}