opengl Keyboard with teapot

#include <cstdlib>          // standard definitions
#include <iostream>         // C++ I/O
#include <cstdio>           // C I/O (for sprintf)
#include <cmath>            // standard definitions

#include <GL/glut.h>            // GLUT
#include <GL/glu.h>         // GLU
#include <GL/gl.h>          // OpenGL

using namespace std;    // make std accessible

float r = 1, g = 0, b = 0, m = 2;

//-----------------------------------------------------------------------
// init
//  Sets up some default OpenGL values.
//-----------------------------------------------------------------------

void init()
{
    glClearColor(0, 0, 0, 0);       // background color
    glClearDepth(1.0);          // background depth value

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60, 1, 1, 1000); // setup a perspective projection

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    gluLookAt(              // set up the camera
        0.0, 0.0, 5.0,      // eye position
        0.0, 0.0, 0.0,      // lookat position
        0.0, 1.0, 0.0);     // up direction

    glEnable(GL_DEPTH_TEST);        // enable hidden surface removal

    glEnable(GL_LIGHTING);      // enable lighting
    glEnable(GL_LIGHT0);        // enable

    float lpos[] = { 5, 5, 5, 0 };
    glLightfv(GL_LIGHT0, GL_POSITION, lpos);

    // glShadeModel(GL_FLAT);       // flat shading
    glShadeModel(GL_SMOOTH);        // smooth shading
}

//-----------------------------------------------------------------------
// display callback function
//  This is called each time application needs to redraw itself.
//  Most of the opengl work is done through this function.
//-----------------------------------------------------------------------

void display()
{
    glClear(
    GL_COLOR_BUFFER_BIT |       // clear the frame buffer (color)
    GL_DEPTH_BUFFER_BIT);       // clear the depth buffer (depths)

    glPushMatrix();         // save the current camera transform

    glRotated(0, 1, 0, 0);  // rotate by rotAngle about y-axis


    glEnable(GL_COLOR_MATERIAL);    // specify object color
    glColor3f(r,g,b);       // redish


    glutSolidTeapot(m);         // draw the teapot

    glPopMatrix();          // restore the modelview matrix
    glFlush();              // force OpenGL to render now

    glutSwapBuffers();          // make the image visible
}

void keyboard(unsigned char k, int x, int y)
{
    if(k == 'r')
    {
        r = 1;
        g = 0;
        b = 0;
    }
    else if(k == 'g')
    {
        r = 0;
        g = 1;
        b = 0;
    }
    else if(k == 'b')
    {
        r = 0;
        g = 0;
        b = 1;
    }


    else exit(0);


    glutPostRedisplay();
}



void usage()
{

    cout.flush();
}



void processSpecialKeys(int key, int x, int y)
{
    if(key == GLUT_KEY_LEFT)
    {
        glTranslatef(-1,0,0);
    }

    else if(key == GLUT_KEY_RIGHT)
    {
        glTranslatef(1,0,0);
    }

    else if(key == GLUT_KEY_F1)
    {
        m++;
    }

    else if(key == GLUT_KEY_F2)
    {
        m--;
    }

    glutPostRedisplay();

}


int main()
{
    usage();                // explain how to use
    glutInitDisplayMode(        // initialize GLUT
    GLUT_DOUBLE |       // use double buffering
    GLUT_DEPTH |        // request memory for z-buffer
    GLUT_RGB );     // set RGB color mode

    glutCreateWindow("Task 3: Teapot Keyboard Effects");    // create the window

    glutDisplayFunc(display);       // call display() to redraw window
    glutKeyboardFunc(keyboard);     // call keyboard() when key is hit
    glutSpecialFunc(processSpecialKeys);

    init();             // our own initializations

    glutMainLoop();         // let GLUT take care of everything
    return 0;
}