OpenGL code for making a moving Car

This source code is for making a simple car which can move from one side to another side.

OpenGL program:-

#include <GL/glut.h>    // Header File For The GLUT Library 
#include <GL/gl.h>    // Header File For The OpenGL32 Library
#include <GL/glu.h>    // Header File For The GLu32 Library
//#include <unistd.h>     // Header File For sleeping.

/* ASCII code for the escape key. */
#define ESCAPE 27

/* The number of our GLUT window */
int window; 

/* rotation angle for the triangle. */
float rtri = 0.0f;

/* rotation angle for the quadrilateral. */
float rquad = 0.0f;

/* A general OpenGL initialization function.  Sets all of the initial parameters. */
// We call this right after our OpenGL window is created.
void InitGL(int Width, int Height)         
{
  // This Will Clear The Background Color To Black
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);     
  glClearDepth(1.0);                // Enables Clearing Of The Depth Buffer
  glDepthFunc(GL_LESS);                // The Type Of Depth Test To Do
  glEnable(GL_DEPTH_TEST);            // Enables Depth Testing
  glShadeModel(GL_SMOOTH);            // Enables Smooth Color Shading

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();                // Reset The Projection Matrix

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);  

  glMatrixMode(GL_MODELVIEW);
}

/* The function called when our window is resized (which shouldn't happen, because we're fullscreen) */
void ReSizeGLScene(int Width, int Height)
{
  if (Height==0)                // Prevent A Divide By Zero If The Window Is Too Small
    Height=1;

  glViewport(0, 0, Width, Height);        // Reset The Current Viewport And Perspective Transformation

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);
  glMatrixMode(GL_MODELVIEW);
}

float ballX = -0.5f;
float ballY = 0.0f;
float ballZ = 0.0f;

void drawBall(void) {
        glColor3f(0.0, 1.0, 0.0); //set ball colour
        glTranslatef(ballX,ballY,ballZ); //moving it toward the screen a bit on creation
        //glRotatef(ballX,ballX,ballY,ballZ);
        glutSolidSphere (0.3, 20, 20); //create ball.
        glTranslatef(ballX+1.5,ballY,ballZ); //moving it toward the screen a bit on creation
        glutSolidSphere (0.3, 20, 20); //
        }


/* The main drawing function. */
void DrawGLScene()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);        // Clear The Screen And The Depth Buffer
  glLoadIdentity();                // Reset The View

  glTranslatef(rtri,0.0f,-6.0f);        // Move Left 1.5 Units And Into The Screen 6.0
   
  //glRotatef(rtri,1.0f,0.0f,0.0f);        // Rotate The Triangle On The Y axis
  // draw a triangle (in smooth coloring mode)
  glBegin(GL_POLYGON);                // start drawing a polygon
  glColor3f(1.0f,0.0f,0.0f);            // Set The Color To Red
  glVertex3f(-1.0f, 1.0f, 0.0f);        // Top left
  glVertex3f(0.4f, 1.0f, 0.0f);
  
  glVertex3f(1.0f, 0.4f, 0.0f);
  
  glColor3f(0.0f,1.0f,0.0f);            // Set The Color To Green
  glVertex3f( 1.0f,0.0f, 0.0f);        // Bottom Right
  glColor3f(0.0f,0.0f,1.0f);            // Set The Color To Blue
  glVertex3f(-1.0f,0.0f, 0.0f);// Bottom Left    

  //glVertex3f();
  glEnd();                    // we're done with the polygon (smooth color interpolation)
  drawBall();
 
  rtri+=0.005f;                    // Increase The Rotation Variable For The Triangle
  if(rtri>2)
      rtri=-2.0f;
  rquad-=15.0f;                    // Decrease The Rotation Variable For The Quad

  // swap the buffers to display, since double buffering is used.
  glutSwapBuffers();
}

/* The function called whenever a key is pressed. */
void keyPressed(unsigned char key, int x, int y) 
{
    /* sleep to avoid thrashing this procedure */
   // usleep(100);

    /* If escape is pressed, kill everything. */
    if (key == ESCAPE) 
    { 
    /* shut down our window */
    glutDestroyWindow(window);
   
    /* exit the program...normal termination. */
    exit(0);                  
    }
}

int main(int argc, char **argv) 
{  
  glutInit(&argc, argv);  

  glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH);  

  /* get a 640 x 480 window */
  glutInitWindowSize(640, 480);  

  /* the window starts at the upper left corner of the screen */
  glutInitWindowPosition(0, 0);  

  /* Open a window */  
  window = glutCreateWindow("Moving Car");  

  /* Register the function to do all our OpenGL drawing. */
  glutDisplayFunc(&DrawGLScene);  

  /* Go fullscreen.  This is as soon as possible. */
  //glutFullScreen();

  /* Even if there are no events, redraw our gl scene. */
  glutIdleFunc(&DrawGLScene);

  /* Register the function called when our window is resized. */
  glutReshapeFunc(&ReSizeGLScene);

  /* Register the function called when the keyboard is pressed. */
  glutKeyboardFunc(&keyPressed);

  /* Initialize our window. */
  InitGL(640, 480);
  
  /* Start Event Processing Engine */  
  glutMainLoop();  

  return 1;
}