FOG.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  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 "glos.h" 
 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include <math.h> 
#include <GL/glaux.h> 
#include <stdio.h> 
 
void myinit(void); 
void renderRedTeapot (GLfloat x, GLfloat y, GLfloat z); 
void CALLBACK cycleFog (AUX_EVENTREC *event); 
void CALLBACK myReshape(GLsizei w, GLsizei h); 
void CALLBACK display(void); 
 
GLint fogMode; 
 
void CALLBACK 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[3]; 
 
    glPushMatrix(); 
    glTranslatef (x, y, z); 
    mat[0] = 0.1745; mat[1] = 0.01175; mat[2] = 0.01175;     
    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); 
    auxSolidTeapot(1.0); 
    glPopMatrix(); 
} 
 
/*  display() draws 5 teapots at different z positions. 
 */ 
void CALLBACK 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 CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    if (!h) return; 
    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_DEPTH16); 
    auxInitPosition (0, 0, 450, 150); 
    auxInitWindow ("Fog"); 
    auxMouseFunc (AUX_LEFTBUTTON, AUX_MOUSEDOWN, cycleFog); 
    myinit(); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}