Bangun Dasar Grafika Segi Empat dan Segi Tiga

#include <GL/glut.h>         
#include <windows.h> 
#include <GL/gl.h>
void init (void) { 
glClearColor (1.0, 1.0, 1.0, 0.0); 
glLineWidth (1.0); 
glColor3f (1.0, 0.0, 0.0);         
glOrtho (-6,6, -6,6, -6,6); 
}             
void Display (void) {     
glClear (GL_COLOR_BUFFER_BIT); 
glBegin (GL_LINES); 
glVertex2f (-5.5, 0.0);     
glColor3f (1.0, 0.0, 0.0);
glVertex2f (5.5, 0.0);     
glEnd ();     
glBegin (GL_LINES);     
glVertex2f (0.0, -5.5); 
glColor3f (1.0, 0.0, 0.0); 
glVertex2f (0.0, 5.5);     
glEnd ();     
         
         
glBegin (GL_TRIANGLES);         
glColor3f (1.0, 0.0, 0.0);     
glVertex2f (1.0, 1.0);     
glColor3f (0.0, 0.0, 1.0);     
glVertex2f (4.0, 1.0);
glColor3f (0.0, 1.0, 0.0);
glVertex2f (1.0, 5.0);
glEnd ();
glBegin (GL_POLYGON);         
glColor3f (0.0, 1.0, 0.0);     
glVertex2f (-1.0, -1.0);     
glColor3f (0.0, 0.0, 1.0);     
glVertex2f (-1.0, -5.0);
glColor3f (1.0, 0.0, 0.0);
glVertex2f (-4.0, -5.0);
glColor3f (1.0, 0.43, 0.78);
glVertex2f (-4.0, -1.0);
glEnd ();
glBegin (GL_POLYGON);         
glColor3f (1.0, 0.43, 0.78);     
glVertex2f (1.0, -1.0);     
glColor3f (0.0, 1.0, 1.0);     
glVertex2f (1.0, -5.0);
glColor3f (1.0, 0.43, 0.78);
glVertex2f (4.0, -5.0);
glColor3f (1.0, 1.0, 0.0);
glVertex2f (4.0, -1.0);
glEnd ();
glBegin (GL_TRIANGLES);         
glColor3f (0.0, 1.0, 1.0);     
glVertex2f (-1.0, 1.0);     
glColor3f (1.0, 0.43, 0.78);     
glVertex2f (-4.0, 1.0);
glColor3f (1.0, 1.0, 0.0);
glVertex2f (-1.0, 5.0);
glEnd ();
glutSwapBuffers ();
}
int main (int argc, char** argv) { 
glutInit (&argc, argv); 
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 
glutInitWindowPosition (0, 0);
glutInitWindowSize (1500, 1500);
glutCreateWindow ("bangun dasar grafik"); 
init ();
glutDisplayFunc (Display);
glutMainLoop ();
return 0;
}