Membuat Bangun Bintang 2D - Pemrograman Grafik

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

void bintangKecil(){
double pi = 3.14;
glBegin(GL_POLYGON);
double r1,r2,x,y;
r2 =100.0;
for(int i=0; i<10; i++){
r1 = i%2 == 0 ? r2 : r2*2.0;
x = r1*sin(i*2*pi/10);
y = r1*cos(i*2*pi/10);
glVertex2d(x,y);
}
glEnd();
}
void render(void){
glClear(GL_COLOR_BUFFER_BIT);
bintangKecil();
glColor3f (1.0, 1.0, 0.0);
glFlush();
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);

glutInitDisplayMode(GLUT_DEPTH | GLUT_SINGLE | GLUT_RGBA);
glutInitWindowPosition(100, 100);
glutInitWindowSize(480, 480);
glutCreateWindow("Bangun Bintang");
glutDisplayFunc(render);
gluOrtho2D(-320.,320.,-320.,320.);
glutMainLoop();
}