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+
+/* Copyright (c) Mark J. Kilgard, 1994. */
+
+/*
+ * (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+ * Unpublished-- rights reserved under the copyright laws of the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.
+ */
+/*
+ *  fogindex.c
+ *  This program demonstrates fog in color index mode.  
+ *  Three cones are drawn at different z values in a linear 
+ *  fog.  32 contiguous colors (from 16 to 47) are loaded 
+ *  with a color ramp.
+ */
+#include <stdlib.h>
+#include <GL/glut.h>
+
+/*  Initialize color map and fog.  Set screen clear color 
+ *  to end of color ramp.
+ */
+#define NUM_COLORS 32
+#define RAMPSTART 16
+
+void 
+myinit(void)
+{
+  int i;
+
+  glEnable(GL_DEPTH_TEST);
+  glDepthFunc(GL_LESS);
+  for (i = 0; i < NUM_COLORS; i++) {
+    GLfloat shade;
+    shade = (GLfloat) (NUM_COLORS - i) / (GLfloat) NUM_COLORS;
+    glutSetColor(16 + i, shade, shade, shade);
+  }
+  glEnable(GL_FOG);
+
+  glFogi(GL_FOG_MODE, GL_LINEAR);
+  glFogi(GL_FOG_INDEX, NUM_COLORS);
+  glFogf(GL_FOG_START, 0.0);
+  glFogf(GL_FOG_END, 4.0);
+  glHint(GL_FOG_HINT, GL_NICEST);
+  glClearIndex((GLfloat) (NUM_COLORS + RAMPSTART - 1));
+}
+
+/*  display() renders 3 cones at different z positions.
+ */
+void 
+display(void)
+{
+  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+  glPushMatrix();
+  glTranslatef(-1.0, -1.0, -1.0);
+  glRotatef(-90.0, 1.0, 0.0, 0.0);
+  glIndexi(RAMPSTART);
+  glutSolidCone(1.0, 2.0, 10, 10);
+  glPopMatrix();
+
+  glPushMatrix();
+  glTranslatef(0.0, -1.0, -2.25);
+  glRotatef(-90.0, 1.0, 0.0, 0.0);
+  glIndexi(RAMPSTART);
+  glutSolidCone(1.0, 2.0, 10, 10);
+  glPopMatrix();
+
+  glPushMatrix();
+  glTranslatef(1.0, -1.0, -3.5);
+  glRotatef(-90.0, 1.0, 0.0, 0.0);
+  glIndexi(RAMPSTART);
+  glutSolidCone(1.0, 2.0, 10, 10);
+  glPopMatrix();
+  glFlush();
+}
+
+void 
+myReshape(int w, int h)
+{
+  glViewport(0, 0, w, h);
+  glMatrixMode(GL_PROJECTION);
+  glLoadIdentity();
+  if (w <= h)
+    glOrtho(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
+      2.0 * (GLfloat) h / (GLfloat) w, 0.0, 10.0);
+  else
+    glOrtho(-2.0 * (GLfloat) w / (GLfloat) h,
+      2.0 * (GLfloat) w / (GLfloat) h, -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)
+{
+  glutInit(&argc, argv);
+  glutInitDisplayMode(GLUT_SINGLE | GLUT_INDEX | GLUT_DEPTH);
+  glutCreateWindow(argv[0]);
+  myinit();
+  glutReshapeFunc(myReshape);
+  glutDisplayFunc(display);
+  glutMainLoop();
+  return 0;             /* ANSI C requires main to return int. */
+}