Using opengl to create a 3D circle

circle_with_opengl.cpp

// circle_assignment.cpp : Defines the entry point for the console application.
//to draw a circle using 3 dimentional graph style

#include "stdafx.h"
#include "glut.h"

GLfloat xRotated, yRotated, zRotated;
GLdouble radius=1;//to set the radius of the circle


 
void display()
{

    glMatrixMode(GL_MODELVIEW);//clears the identity matrix
    glClear(GL_COLOR_BUFFER_BIT);//clears the buffer drawing

    glLoadIdentity();
    // traslate the draw by z = -4.0
    // Note this when you decrease z like -8.0 the drawing will looks far , or smaller.
    glTranslatef(0.0,0.0,-5.0);
    
    glColor3f(0.9, 0.0, 0.9); // Red color used to draw.
    // changing in transformation matrix.
    // rotation about X axis
    glRotatef(xRotated,1.0,0.0,0.0);
    
    glRotatef(yRotated,0.0,1.0,0.0);// rotation about Y axis
    
    glRotatef(zRotated,0.0,0.0,1.0);// rotation about Z axis
    
    glScalef(1.0,1.0,1.0);// scaling transfomation 
    // NOTE: built-in (glut library) function , draw you a sphere.
    glutSolidSphere(radius,20,20);
    
     
    glFlush();  // This makes the drawing happen as soon as possible      
   
}

void init(int x, int y)
{
    if (y == 0 || x == 0) return;   
    glMatrixMode(GL_PROJECTION);  
    glLoadIdentity(); 
    gluPerspective(39.0,(GLdouble)x/(GLdouble)y,0.6,21.0);
    glMatrixMode(GL_MODELVIEW);
    glViewport(0,0,x,y);  //Use the whole window for rendering
}
int main (int argc, char **argv)
{
    glutInit(&argc, argv); 
    glutInitWindowSize(500,500);
    glutCreateWindow("Our purple Sphere");
    xRotated = yRotated = zRotated = 30.0;
    xRotated=43;
    yRotated=50;
 
    glutDisplayFunc(display);
    glutReshapeFunc(init);
    glutMainLoop();
    return 0;
}