Phong illumination model

/*
* This is Phong illumination model, an illumination model for
* non-perfect reflectors.This is the most popular illumination model
* although does not actually explain the real light source.
*/
 
#include <GL/glut.h>
 
void init(void)
{
    GLfloat mat_shininess[] = { 10.0 };
    //set light position
    GLfloat light_position[] = { 1.0, 1.0, 2.0, 1.0 };
     
    //define colors for ambient, diffuse, and specular light     
    GLfloat light_Ka[] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat light_Kd[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat light_Ks[] = { 1.0, 1.0, 1.0, 1.0 };
     
    glClearColor (1.0, 0.0, 0.0, 0.0);
    glShadeModel (GL_SMOOTH);
 
    /*GL_LIGHT0 means there is only one light source
    * we can actually have maximum of 8 light sources
    * denoted as GL_LIGHT0, GL_LIGHT1,…,GL_LIGHT7
    */
    glLightfv(GL_LIGHT0, GL_POSITION, light_position); 
     
    //attach defined lights to light source
    glLightfv(GL_LIGHT0, GL_AMBIENT, light_Ka); 
    glLightfv(GL_LIGHT0, GL_DIFFUSE, light_Kd);
    glLightfv(GL_LIGHT0, GL_SPECULAR, light_Ks); 

    glMaterialfv(GL_FRONT, GL_SPECULAR, light_Ks);
    glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
   
     
    //enables light
    glEnable(GL_LIGHTING);
     
    //enables this particular source.
    glEnable(GL_LIGHT0);
 
    glEnable(GL_DEPTH_TEST);
}
void display(void)
{
      glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      glutSolidSphere (1.0, 20, 16);
      glutSwapBuffers();
   
}
void reshape (int w, int h)
{
    glViewport (0, 0, (GLsizei) w, (GLsizei) h);
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity();
    if (w <= h)
        glOrtho (-1.5, 1.5, -1.5*(GLfloat)h/(GLfloat)w, 1.5*(GLfloat)h/(GLfloat)w, -10.0, 10.0);
    else
        glOrtho (-1.5*(GLfloat)w/(GLfloat)h, 1.5*(GLfloat)w/(GLfloat)h, -1.5, 1.5, -10.0, 10.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}
int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize (500, 500);
    glutInitWindowPosition (100, 100);
    glutCreateWindow (”Single-Point Light Source”);
    init();
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}