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.
/* 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 * Unpublished-- rights reserved under the copyright laws of the * United States.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. */ #include <GL/openglut.h> #include <stdlib.h> #include <math.h> GLint fogMode; void selectFog(int mode) { switch(mode) { case GL_LINEAR: glFogf(GL_FOG_START, 1.0); glFogf(GL_FOG_END, 5.0); /* falls through */ case GL_EXP2: case GL_EXP: glFogiv(GL_FOG_MODE, (int *) &mode); glutPostRedisplay(); break; case 0: exit(0); } } /* 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); glutSolidTeapot(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(); } static void key(unsigned char k, int x, int y) { switch (k) { case 27: /* Escape */ exit(0); break; default: return; } glutPostRedisplay(); } /* 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_RGB | GLUT_DEPTH); glutInitWindowSize(450, 150); glutCreateWindow(argv[0]); myinit(); glutReshapeFunc(myReshape); glutDisplayFunc(display); glutCreateMenu(selectFog); glutAddMenuEntry("Fog EXP", GL_EXP); glutAddMenuEntry("Fog EXP2", /*GL_EXP2*/ 0xffff); glutAddMenuEntry("Fog LINEAR", GL_LINEAR); glutAddMenuEntry("Quit", 0); glutAttachMenu(GLUT_RIGHT_BUTTON); glutKeyboardFunc(key); glutMainLoop(); return 0; /* ANSI C requires main to return int. */ }