AIM.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  aim.c 
 *  This program calculates the fovy (field of view angle 
 *  in the y direction), by using trigonometry, given the 
 *  size of an object and its size. 
 */ 
#include "glos.h" 
 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include <math.h> 
#include <GL/glaux.h> 
#include <stdio.h> 
 
void myinit(void); 
GLdouble calculateAngle (double size, double distance); 
void CALLBACK display(void); 
void CALLBACK myReshape(GLsizei w, GLsizei h); 
 
void myinit (void) { 
    glShadeModel (GL_FLAT); 
} 
 
/*  Clear the screen.  Set the current color to white. 
 *  Draw the wire frame cube and sphere. 
 */ 
void CALLBACK display (void) 
{ 
    glClear(GL_COLOR_BUFFER_BIT); 
    glColor3f (1.0, 1.0, 1.0); 
 
    glLoadIdentity (); 
/*  glTranslatef() as viewing transformation    */ 
    glTranslatef (0.0, 0.0, -5.0); 
    auxWireCube(2.0); 
    auxWireSphere(1.0); 
    glFlush(); 
} 
 
#define PI  3.1415926535 
 
/*  atan2 () is a system math routine which calculates 
 *  the arctangent of an angle, given length of the  
 *  opposite and adjacent sides of a right triangle. 
 *  atan2 () is not an OpenGL routine. 
 */ 
GLdouble calculateAngle (double size, double distance) 
{ 
    GLdouble radtheta, degtheta; 
     
    radtheta = 2.0 * atan2 (size/2.0, distance); 
    degtheta = (180.0 * radtheta) / PI; 
    //printf ("degtheta is %lf\n", degtheta); 
    return ((GLdouble) degtheta); 
} 
 
/*  Called when the window is first opened and whenever  
 *  the window is reconfigured (moved or resized). 
 */ 
void CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    GLdouble theta; 
 
    if(!h) return; 
    glViewport(0, 0, w, h); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    theta = calculateAngle (2.0, 5.0); 
    gluPerspective(theta, (GLfloat) w/(GLfloat) h, 1.0, 20.0); 
    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
} 
 
/*  Main Loop 
 *  Open window with initial window size, title bar,  
 *  RGBA display mode, and handle input events. 
 */ 
int main(int argc, char** argv) 
{ 
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB); 
    auxInitPosition (0, 0, 500, 500); 
    auxInitWindow ("Field of View Angle"); 
    myinit (); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}