/*
 * (c) Copyright 1993, Silicon Graphics, Inc.
 * ALL RIGHTS RESERVED 
 * Permission to use, copy, modify, and distribute this software for 
 * any purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation, and that 
 * the name of Silicon Graphics, Inc. not be used in advertising
 * or publicity pertaining to distribution of the software without specific,
 * written prior permission. 
 *
 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
 * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
 * 
 * US Government Users Restricted Rights 
 * Use, duplication, or disclosure by the Government is subject to
 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
 * clause at DFARS 252.227-7013 and/or in similar or successor
 * clauses in the FAR or the DOD or NASA FAR Supplement.
 * Unpublished-- rights reserved under the copyright laws of the
 * United States.  Contractor/manufacturer is Silicon Graphics,
 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
 *
 * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
 */
/*
 *  tea.c
 *  This program demonstrates two-sided lighting and compares
 *  it with one-sided lighting.  Three teapots are drawn, with
 *  a clipping plane to expose the interior of the objects.
 */
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdlib.h>
#include <GL/glaux.h>

/*
 * Initialize light source.
 */
void myinit(void)
{
  GLfloat light_ambient[] =
  {0.0, 0.0, 0.0, 1.0};
  GLfloat light_diffuse[] =
  {1.0, 1.0, 1.0, 1.0};
  GLfloat light_specular[] =
  {1.0, 1.0, 1.0, 1.0};

/*
 * light_position is NOT default value  
 */
  GLfloat light_position[] =
  {1.0, 1.0, 1.0, 0.0};

  glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
  glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
  glLightfv(GL_LIGHT0, GL_POSITION, light_position);

  glFrontFace(GL_CW);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_AUTO_NORMAL);
  glEnable(GL_NORMALIZE);
  glDepthFunc(GL_LESS);
  glEnable(GL_DEPTH_TEST);
}

void display(void)
{
  GLdouble eqn[4] =
  {1.0, 0.0, -1.0, 1.0};
  GLfloat two_side_on[] =
  {GL_TRUE};
  GLfloat two_side_off[] =
  {GL_FALSE};
  GLfloat mat_diffuse[] =
  {0.8, 0.8, 0.8, 1.0};
  GLfloat back_diffuse[] =
  {0.8, 0.2, 0.8, 1.0};

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

  glPushMatrix();
  glClipPlane(GL_CLIP_PLANE0, eqn);					       /*
									        * slice objects   
									        */
  glEnable(GL_CLIP_PLANE0);

  glPushMatrix();
  glTranslatef(0.0, 2.0, 0.0);
  auxSolidTeapot(1.0);							       /*
									        * one-sided lighting   
									        */
  glPopMatrix();

  /*
   * two-sided lighting, but same material        
   */
  glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE);
  glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, mat_diffuse);
  glPushMatrix();
  glTranslatef(0.0, 0.0, 0.0);
  auxSolidTeapot(1.0);
  glPopMatrix();

  /*
   * two-sided lighting, two different materials  
   */
  glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
  glMaterialfv(GL_BACK, GL_DIFFUSE, back_diffuse);
  glPushMatrix();
  glTranslatef(0.0, -2.0, 0.0);
  auxSolidTeapot(1.0);
  glPopMatrix();

  glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_FALSE);
  glDisable(GL_CLIP_PLANE0);
  glPopMatrix();
  glFlush();
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if (w <= h)
    glOrtho(-4.0, 4.0, -4.0 * (GLfloat) h / (GLfloat) w,
	    4.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
  else
    glOrtho(-4.0 * (GLfloat) w / (GLfloat) h,
	    4.0 * (GLfloat) w / (GLfloat) h, -4.0, 4.0, -10.0, 10.0);
  glMatrixMode(GL_MODELVIEW);
}

/*
 * Main Loop
 * *  Open window with initial window size, title bar, 
 * *  RGBA display mode, and handle input events.
 */
int main(int argc, char **argv)
{
  auxInitDisplayMode(AUX_SINGLE | AUX_RGB | AUX_DEPTH);
  auxInitPosition(0, 0, 500, 500);
  if (!auxInitWindow(argv[0]))
    auxQuit();
  myinit();
  auxReshapeFunc(myReshape);
  auxMainLoop(display);
  return 0;
}