progs/redbook/feedback.c

   1 /*
   2  * Copyright (c) 1993-1997, Silicon Graphics, Inc.
   3  * ALL RIGHTS RESERVED
   4  * Permission to use, copy, modify, and distribute this software for
   5  * any purpose and without fee is hereby granted, provided that the above
   6  * copyright notice appear in all copies and that both the copyright notice
   7  * and this permission notice appear in supporting documentation, and that
   8  * the name of Silicon Graphics, Inc. not be used in advertising
   9  * or publicity pertaining to distribution of the software without specific,
  10  * written prior permission.
  11  *
  12  * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
  13  * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
  14  * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
  15  * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
  16  * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
  17  * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
  18  * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
  19  * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
  20  * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
  21  * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
  22  * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
  23  * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
  24  *
  25  * US Government Users Restricted Rights
  26  * Use, duplication, or disclosure by the Government is subject to
  27  * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
  28  * (c)(1)(ii) of the Rights in Technical Data and Computer Software
  29  * clause at DFARS 252.227-7013 and/or in similar or successor
  30  * clauses in the FAR or the DOD or NASA FAR Supplement.
  31  * Unpublished-- rights reserved under the copyright laws of the
  32  * United States.  Contractor/manufacturer is Silicon Graphics,
  33  * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
  34  *
  35  * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
  36  */
  37
  38 /*
  39  * feedback.c
  40  * This program demonstrates use of OpenGL feedback.  First,
  41  * a lighting environment is set up and a few lines are drawn.
  42  * Then feedback mode is entered, and the same lines are
  43  * drawn.  The results in the feedback buffer are printed.
  44  */
  45 #include <GL/glut.h>
  46 #include <stdlib.h>
  47 #include <stdio.h>
  48
  49 /*  Initialize lighting.
  50  */
  51 static void init(void)
  52 {
  53    glEnable(GL_LIGHTING);
  54    glEnable(GL_LIGHT0);
  55 }
  56
  57 /* Draw a few lines and two points, one of which will
  58  * be clipped.  If in feedback mode, a passthrough token
  59  * is issued between the each primitive.
  60  */
  61 static void drawGeometry (GLenum mode)
  62 {
  63    glBegin (GL_LINE_STRIP);
  64    glNormal3f (0.0, 0.0, 1.0);
  65    glVertex3f (30.0, 30.0, 0.0);
  66    glVertex3f (50.0, 60.0, 0.0);
  67    glVertex3f (70.0, 40.0, 0.0);
  68    glEnd ();
  69    if (mode == GL_FEEDBACK)
  70       glPassThrough (1.0);
  71    glBegin (GL_POINTS);
  72    glVertex3f (-100.0, -100.0, -100.0);  /*  will be clipped  */
  73    glEnd ();
  74    if (mode == GL_FEEDBACK)
  75       glPassThrough (2.0);
  76    glBegin (GL_POINTS);
  77    glNormal3f (0.0, 0.0, 1.0);
  78    glVertex3f (50.0, 50.0, 0.0);
  79    glEnd ();
  80 }
  81
  82 /* Write contents of one vertex to stdout.      */
  83 static void print3DcolorVertex (GLint size, GLint *count,
  84                                 GLfloat *buffer)
  85 {
  86    int i;
  87
  88    printf ("  ");
  89    for (i = 0; i < 7; i++) {
  90       printf ("%4.2f ", buffer[size-(*count)]);
  91       *count = *count - 1;
  92    }
  93    printf ("\n");
  94 }
  95
  96 /*  Write contents of entire buffer.  (Parse tokens!)   */
  97 static void printBuffer(GLint size, GLfloat *buffer)
  98 {
  99    GLint count;
 100    GLfloat token;
 101
 102    count = size;
 103    while (count) {
 104       token = buffer[size-count]; count--;
 105       if (token == GL_PASS_THROUGH_TOKEN) {
 106          printf ("GL_PASS_THROUGH_TOKEN\n");
 107          printf ("  %4.2f\n", buffer[size-count]);
 108          count--;
 109       }
 110       else if (token == GL_POINT_TOKEN) {
 111          printf ("GL_POINT_TOKEN\n");
 112          print3DcolorVertex (size, &count, buffer);
 113       }
 114       else if (token == GL_LINE_TOKEN) {
 115          printf ("GL_LINE_TOKEN\n");
 116          print3DcolorVertex (size, &count, buffer);
 117          print3DcolorVertex (size, &count, buffer);
 118       }
 119       else if (token == GL_LINE_RESET_TOKEN) {
 120          printf ("GL_LINE_RESET_TOKEN\n");
 121          print3DcolorVertex (size, &count, buffer);
 122          print3DcolorVertex (size, &count, buffer);
 123       }
 124    }
 125 }
 126
 127 static void display(void)
 128 {
 129    GLfloat feedBuffer[1024];
 130    GLint size;
 131
 132    glMatrixMode (GL_PROJECTION);
 133    glLoadIdentity ();
 134    glOrtho (0.0, 100.0, 0.0, 100.0, 0.0, 1.0);
 135
 136    glClearColor (0.0, 0.0, 0.0, 0.0);
 137    glClear(GL_COLOR_BUFFER_BIT);
 138    drawGeometry (GL_RENDER);
 139
 140    glFeedbackBuffer (1024, GL_3D_COLOR, feedBuffer);
 141    (void) glRenderMode (GL_FEEDBACK);
 142    drawGeometry (GL_FEEDBACK);
 143
 144    size = glRenderMode (GL_RENDER);
 145    printBuffer (size, feedBuffer);
 146
 147    glFinish();
 148 }
 149
 150 /* ARGSUSED1 */
 151 static void keyboard(unsigned char key, int x, int y)
 152 {
 153    switch (key) {
 154       case 27:
 155          exit(0);
 156          break;
 157    }
 158 }
 159
 160 /*  Main Loop  */
 161 int main(int argc, char** argv)
 162 {
 163    glutInit(&argc, argv);
 164    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
 165    glutInitWindowSize (100, 100);
 166    glutInitWindowPosition (100, 100);
 167    glutCreateWindow(argv[0]);
 168    init();
 169    glutDisplayFunc(display);
 170    glutKeyboardFunc (keyboard);
 171    glutMainLoop();
 172    return 0;
 173 }