/*
 * (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 * Unpublished-- rights reserved under the copyright laws of the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.
 */
/*
 *  fog.c
 *  This program draws 5 red teapots, each at a different 
 *  z distance from the eye, in different types of fog.  
 *  Pressing the left mouse button chooses between 3 types of 
 *  fog:  exponential, exponential squared, and linear.  
 *  In this program, there is a fixed density value, as well 
 *  as fixed start and end values for the linear fog.
 */
#include <GL/gl.h>
#include <GL/glu.h>
#include <math.h>
#include <stdio.h>
#include <GL/glaux.h>

GLint fogMode;

void cycleFog(AUX_EVENTREC * event)
{
  if (fogMode == GL_EXP) {
    fogMode = GL_EXP2;
    printf("Fog mode is GL_EXP2\n");
  }
  else if (fogMode == GL_EXP2) {
    fogMode = GL_LINEAR;
    printf("Fog mode is GL_LINEAR\n");
    glFogf(GL_FOG_START, 1.0);
    glFogf(GL_FOG_END, 5.0);
  }
  else if (fogMode == GL_LINEAR) {
    fogMode = GL_EXP;
    printf("Fog mode is GL_EXP\n");
  }
  glFogi(GL_FOG_MODE, fogMode);
}

/*
 * Initialize z-buffer, projection matrix, light source, 
 * *  and lighting model.  Do not specify a material property here.
 */
void myinit(void)
{
  GLfloat position[] =
  {0.0, 3.0, 3.0, 0.0};
  GLfloat local_view[] =
  {0.0};

  glEnable(GL_DEPTH_TEST);
  glDepthFunc(GL_LESS);

  glLightfv(GL_LIGHT0, GL_POSITION, position);
  glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, local_view);

  glFrontFace(GL_CW);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glEnable(GL_AUTO_NORMAL);
  glEnable(GL_NORMALIZE);
  glEnable(GL_FOG);
  {
    GLfloat fogColor[4] =
    {0.5, 0.5, 0.5, 1.0};

    fogMode = GL_EXP;
    glFogi(GL_FOG_MODE, fogMode);
    glFogfv(GL_FOG_COLOR, fogColor);
    glFogf(GL_FOG_DENSITY, 0.35);
    glHint(GL_FOG_HINT, GL_DONT_CARE);
    glClearColor(0.5, 0.5, 0.5, 1.0);
  }
}

void renderRedTeapot(GLfloat x, GLfloat y, GLfloat z)
{
  float mat[4];

  glPushMatrix();
  glTranslatef(x, y, z);
  mat[0] = 0.1745;
  mat[1] = 0.01175;
  mat[2] = 0.01175;
  mat[3] = 1.0;
  glMaterialfv(GL_FRONT, GL_AMBIENT, mat);
  mat[0] = 0.61424;
  mat[1] = 0.04136;
  mat[2] = 0.04136;
  glMaterialfv(GL_FRONT, GL_DIFFUSE, mat);
  mat[0] = 0.727811;
  mat[1] = 0.626959;
  mat[2] = 0.626959;
  glMaterialfv(GL_FRONT, GL_SPECULAR, mat);
  glMaterialf(GL_FRONT, GL_SHININESS, 0.6 * 128.0);
  glColor3f(1, 1, 1);
  auxSolidTeapot(1.0);
  glPopMatrix();
}

/*
 * display() draws 5 teapots at different z positions.
 */
void display(void)
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  renderRedTeapot(-4.0, -0.5, -1.0);
  renderRedTeapot(-2.0, -0.5, -2.0);
  renderRedTeapot(0.0, -0.5, -3.0);
  renderRedTeapot(2.0, -0.5, -4.0);
  renderRedTeapot(4.0, -0.5, -5.0);
  glFlush();
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if (w <= (h * 3))
    glOrtho(-6.0, 6.0, -2.0 * ((GLfloat) h * 3) / (GLfloat) w,
	    2.0 * ((GLfloat) h * 3) / (GLfloat) w, 0.0, 10.0);
  else
    glOrtho(-6.0 * (GLfloat) w / ((GLfloat) h * 3),
	    6.0 * (GLfloat) w / ((GLfloat) h * 3), -2.0, 2.0, 0.0, 10.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

/*
 * Main Loop
 * *  Open window with initial window size, title bar, 
 * *  RGBA display mode, depth buffer, and handle input events.
 */
int main(int argc, char **argv)
{
  auxInitDisplayMode(AUX_SINGLE | AUX_RGB | AUX_DEPTH);
  auxInitPosition(0, 0, 450, 150);
  if (!auxInitWindow(argv[0]))
    auxQuit();
  auxMouseFunc(AUX_LEFTBUTTON, AUX_MOUSEDOWN, cycleFog);
  myinit();
  auxReshapeFunc(myReshape);
  auxMainLoop(display);
  return 0;
}