Membuat Lingkaran 2D - Pemrograman Grafik

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

const double PI = 3.141592653589793;
int i,radius,jumlah_titik,x_tengah,y_tengah;
void Draw(){
glClearColor(1.0,1.0,1.0,1.0);
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 0.0, 1.0);
glBegin(GL_POLYGON);
radius=40;
jumlah_titik=100;
x_tengah=50;
y_tengah=50;
for (i=0;i<=360;i++)
    {
float sudut=i*(2*PI/jumlah_titik);
float x=x_tengah+radius*cos(sudut);
float y=y_tengah+radius*sin(sudut);
glVertex2f(x/100,y/100);
    }
glEnd();
glFlush();
}

void Initialize() {
glClearColor(0.0, 0.0, 0.0, 0.0);
glLoadIdentity();
glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);
}

int main(int iArgc, char** cppArgv){
glutInit(&iArgc, cppArgv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(200, 200);
glutInitWindowSize(400, 400);
//gluOrtho2D(-150., 150., -150., 150);
glutCreateWindow("Bangun Lingkaran");
Initialize();
glutDisplayFunc(Draw);
glutMainLoop();
return 0;

}