/*
 *  lightsphere.cpp, based on light.c from OpenGL book.
 *  This program demonstrates the use of the OpenGL lighting
 *  model.  A sphere is drawn using a grey material characteristic.
 *  Two light sources illuminate the object.
 */
#include <GL/glut.h>
#include <iostream>

int flat; // flag for flat shading (1) or smooth shading (0)


/*  Initialize material property, light sources, lighting model,
 *  and depth buffer.
 */
void init(void) 
{
  flat = 1;

  GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
  GLfloat mat_shininess[] = { 50.0 };
  GLfloat light_position[] = { 1.0, 1.0, 1.0, 0.0 };

  GLfloat light1_ambient[] = { 0.2, 0.2, 0.2, 1.0 };
  GLfloat light1_diffuse[] = { 1.0, 0.0, 0.0, 1.0 };
  GLfloat light1_specular[] = { 1.0, 0.0, 0.0, 1.0 };
  GLfloat light1_position[] = { -1.0, 1.0, 1.0, 1.0 };
  
  glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
  glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
  glLightfv(GL_LIGHT0, GL_POSITION, light_position);

  glLightfv(GL_LIGHT1, GL_AMBIENT, light1_ambient);
  glLightfv(GL_LIGHT1, GL_DIFFUSE, light1_diffuse);
  glLightfv(GL_LIGHT1, GL_SPECULAR, light1_specular);
  glLightfv(GL_LIGHT1, GL_POSITION, light1_position);

  glEnable(GL_LIGHT0);
  glEnable(GL_LIGHT1);
  glEnable(GL_LIGHTING);
  glEnable(GL_DEPTH_TEST);

}

void display(void)
{
  glClearColor (0.0, 0.0, 0.0, 0.0);

  if (flat)
    glShadeModel(GL_FLAT);
  else
    glShadeModel(GL_SMOOTH);

  glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glutSolidSphere (1.0, 20, 16);
  glFlush ();
}

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();
}

void keyboard(unsigned char key, int x, int y)
{
  if (key == 'q' || key == 'Q')
    exit(0);
  else if (key == 'f'){
    flat = 1;
    glutPostRedisplay();
  }
  else if (key == 's'){
    flat = 0;
    glutPostRedisplay();
  }
}

int main(int argc, char** argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize (500, 500); 
  glutInitWindowPosition (100, 100);
  glutCreateWindow (argv[0]);
  init ();
  glutDisplayFunc(display); 
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  glutMainLoop();
  return 0;
}