unproject.c

/*
 * Copyright (c) 1993-1997, 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 * Unpublished-- rights reserved under the copyright laws of the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.
 */

/*
 *  unproject.c
 *  When the left mouse button is pressed, this program 
 *  reads the mouse position and determines two 3D points 
 *  from which it was transformed.  Very little is displayed.
 */
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glFlush();
}

/* Change these values for a different transformation  */
void reshape(int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluPerspective (45.0, (GLfloat) w/(GLfloat) h, 1.0, 100.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

void mouse(int button, int state, int x, int y) 
{
   GLint viewport[4];
   GLdouble mvmatrix[16], projmatrix[16];
   GLint realy;  /*  OpenGL y coordinate position  */
   GLdouble wx, wy, wz;  /*  returned world x, y, z coords  */

   switch (button) {
      case GLUT_LEFT_BUTTON:
         if (state == GLUT_DOWN) {
            glGetIntegerv (GL_VIEWPORT, viewport);
            glGetDoublev (GL_MODELVIEW_MATRIX, mvmatrix);
            glGetDoublev (GL_PROJECTION_MATRIX, projmatrix);
/*  note viewport[3] is height of window in pixels  */
            realy = viewport[3] - (GLint) y - 1;
            printf ("Coordinates at cursor are (%4d, %4d)\n", x, realy);
            gluUnProject ((GLdouble) x, (GLdouble) realy, 0.0, 
               mvmatrix, projmatrix, viewport, &wx, &wy, &wz); 
            printf ("World coords at z=0.0 are (%f, %f, %f)\n", 
               wx, wy, wz);
            gluUnProject ((GLdouble) x, (GLdouble) realy, 1.0, 
               mvmatrix, projmatrix, viewport, &wx, &wy, &wz); 
            printf ("World coords at z=1.0 are (%f, %f, %f)\n", 
               wx, wy, wz);
         }
         break;
      case GLUT_RIGHT_BUTTON:
         if (state == GLUT_DOWN)
            exit(0);
         break;
      default:
         break;
   }
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
   }
}
   
/* 
 *  Open window, register input callback functions
 */
int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (500, 500); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   glutDisplayFunc(display); 
   glutReshapeFunc(reshape); 
   glutKeyboardFunc (keyboard);
   glutMouseFunc(mouse);
   glutMainLoop();
   return 0;
}