Write a glut program to implement animation of squashing and rotating ball

CODE:

#include <stdio.h>

#include <stdlib.h>

#include <windows.h>

#include <MATH.h>

#if defined(__APPLE__)

#include <GLUT/glut.h>

#else

#include <GL/glut.h>

#endif

#define PI 3.1415926535898

double xpos, ypos, ydir, xdir;        

double sx, sy, squash;         

double rot;            

#define PI 3.1415926535898

GLint circle_points = 100;

void MyCircle2f(GLfloat centerx, GLfloat centery, GLfloat radius){

  GLint i;

  GLdouble angle;

  glBegin(GL_POLYGON);

  for (i = 0; i < circle_points; i++) {   

    angle = 2*PI*i/circle_points;

    glVertex2f(centerx+radius*cos(angle), centery+radius*sin(angle));

  }

  glEnd();

}

GLfloat RadiusOfBall = 15.;

void draw_ball() {

  glColor3f(0.6,0.3,0.);

  glScalef(1.3,1.,1.);

  MyCircle2f(0.,0.,RadiusOfBall);

}

void Display(void)

{

  glutSwapBuffers();

  glClear(GL_COLOR_BUFFER_BIT);

  xpos = 80.;

       if (ypos == RadiusOfBall && ydir == -1  ) {

              sy = sy*squash ;

              if (sy < 0.8)

                     squash = 1.1;

              else if (sy > 1.) {

                     sy = 1.;

                     squash = 0.9;

                     ydir = 1;

              }

              sx = 1./sy;

       }

       else {

       ypos = ypos+ydir *1.5 - (1.-sy)*RadiusOfBall;

       if (ypos == 120-RadiusOfBall)

              ydir = -1;

       else if (ypos <RadiusOfBall)

              ydir = 1;

       }

       rot = rot+2.;

       if (rot >= 360)

    rot = 0;

  glLoadIdentity();

  glTranslatef(xpos,ypos, 0.);

  glScalef(sx,sy, 1.);

  glRotatef(rot, 0.,0.,1.);

  draw_ball();

 glutPostRedisplay();

  }

void reshape (int w, int h)

{

   glViewport (0, 0, (GLsizei) w, (GLsizei) h);

   glMatrixMode (GL_PROJECTION);

   glLoadIdentity ();

   gluOrtho2D(0.0, 160.0, 0.0, 120.0);

   glMatrixMode(GL_MODELVIEW);

   glLoadIdentity ();

}

void init(void){

  glClearColor(0.0,0.8,0.0,1.0);

  xpos = 60; ypos = RadiusOfBall; xdir = 1; ydir = 1;

  sx = 1.; sy = 1.; squash = 0.9;

  rot = 0;

}

void main(int argc, char* argv[])

{

  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);

  glutInitWindowSize (320, 240);  

  glutCreateWindow("Bouncing Ball");

  init();

  glutDisplayFunc(Display);

  glutReshapeFunc(reshape);

  glutMainLoop();

}

OUTPUT: