fogindex.c

OpenGL学习资料

/*
 * Copyright (c) 1993-1999, 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 * Unpublished-- rights reserved under the copyright laws of the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(R) is a registered trademark of Silicon Graphics, Inc.
 */

/*
 *  fogindex.c
 *  This program draws 5 wireframe spheres, each at 
 *  a different z distance from the eye, in linear fog.
 */
#include <GL/glut.h>
#include <math.h>
#include <stdlib.h>
#include <stdio.h>

/*  Initialize color map and fog.  Set screen clear color
 *  to end of color ramp.
 */
#define NUMCOLORS 32
#define RAMPSTART 16

static void init(void)
{
   int i;

   glEnable(GL_DEPTH_TEST);

   for (i = 0; i < NUMCOLORS; i++) {
      GLfloat shade;
      shade = (GLfloat) (NUMCOLORS-i)/(GLfloat) NUMCOLORS;
      glutSetColor (RAMPSTART + i, shade, shade, shade);
   }
   glEnable(GL_FOG);

   glFogi (GL_FOG_MODE, GL_LINEAR);
   glFogi (GL_FOG_INDEX, NUMCOLORS);
   glFogf (GL_FOG_START, 1.0);
   glFogf (GL_FOG_END, 6.0);
   glHint (GL_FOG_HINT, GL_NICEST);
   glClearIndex((GLfloat) (NUMCOLORS+RAMPSTART-1));
}

static void renderSphere (GLfloat x, GLfloat y, GLfloat z)
{
   glPushMatrix();
   glTranslatef (x, y, z);
   glutWireSphere(0.4, 16, 16);
   glPopMatrix();
}

/*  display() draws 5 spheres at different z positions.
 */
void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glIndexi (RAMPSTART);

   renderSphere (-2., -0.5, -1.0);
   renderSphere (-1., -0.5, -2.0);
   renderSphere (0., -0.5, -3.0);
   renderSphere (1., -0.5, -4.0);
   renderSphere (2., -0.5, -5.0);

   glFlush();
}

void reshape(int w, int h)
{
   glViewport(0, 0, w, h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if (w <= h)
      glOrtho (-2.5, 2.5, -2.5*(GLfloat)h/(GLfloat)w,
         2.5*(GLfloat)h/(GLfloat)w, -10.0, 10.0);
   else
      glOrtho (-2.5*(GLfloat)w/(GLfloat)h,
         2.5*(GLfloat)w/(GLfloat)h, -2.5, 2.5, -10.0, 10.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity ();
}

void keyboard(unsigned char key, int x, int y)
{

   switch (key) {
      case 27:
         exit(0);
   }
}


/*  Main Loop
 *  Open window with initial window size, title bar, 
 *  color index mode, depth buffer, and handle input events.
 */
int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_INDEX | GLUT_DEPTH);
   glutInitWindowSize(500, 500);
   glutCreateWindow(argv[0]);
   init();
   glutReshapeFunc (reshape);
   glutKeyboardFunc (keyboard);
   glutDisplayFunc (display);
   glutMainLoop();
   return 0;
}