/*
 * (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 * Unpublished-- rights reserved under the copyright laws of the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.
 */
/*
 *  feedback.c
 *  This program demonstrates use of OpenGL feedback.  First,
 *  a lighting environment is set up and a few lines are drawn.
 *  Then feedback mode is entered, and the same lines are 
 *  drawn.  The results in the feedback buffer are printed.
 */
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdio.h>
#include <stdlib.h>
#include <GL/glaux.h>

/*
 * Initialize lighting.
 */
void myinit(void)
{
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
}

/*
 * Draw a few lines and two points, one of which will 
 * *  be clipped.  If in feedback mode, a passthrough token 
 * *  is issued between the each primitive.
 */
void drawGeometry(GLenum mode)
{
  glBegin(GL_LINE_STRIP);
  glNormal3f(0.0, 0.0, 1.0);
  glVertex3f(30.0, 30.0, 0.0);
  glVertex3f(50.0, 60.0, 0.0);
  glVertex3f(70.0, 40.0, 0.0);
  glEnd();
  if (mode == GL_FEEDBACK)
    glPassThrough(1.0);
  glBegin(GL_POINTS);
  glVertex3f(-100.0, -100.0, -100.0);					       /*
									        * will be clipped  
									        */
  glEnd();
  if (mode == GL_FEEDBACK)
    glPassThrough(2.0);
  glBegin(GL_POINTS);
  glNormal3f(0.0, 0.0, 1.0);
  glVertex3f(50.0, 50.0, 0.0);
  glEnd();
}

/*
 * Write contents of one vertex to stdout.      
 */
void print3DcolorVertex(GLint size,
			GLint * count, GLfloat * buffer)
{
  int i;

  printf("  ");
  for (i = 0; i < 7; i++) {
    printf("%4.2f ", buffer[size - (*count)]);
    *count = *count - 1;
  }
  printf("\n");
}

/*
 * Write contents of entire buffer.  (Parse tokens!)    
 */
void printBuffer(GLint size, GLfloat * buffer)
{
  GLint count;
  GLfloat token;

  count = size;
  while (count) {
    token = buffer[size - count];
    count--;
    if (token == GL_PASS_THROUGH_TOKEN) {
      printf("GL_PASS_THROUGH_TOKEN\n");
      printf("  %4.2f\n", buffer[size - count]);
      count--;
    }
    else if (token == GL_POINT_TOKEN) {
      printf("GL_POINT_TOKEN\n");
      print3DcolorVertex(size, &count, buffer);
    }
    else if (token == GL_LINE_TOKEN) {
      printf("GL_LINE_TOKEN\n");
      print3DcolorVertex(size, &count, buffer);
      print3DcolorVertex(size, &count, buffer);
    }
    else if (token == GL_LINE_RESET_TOKEN) {
      printf("GL_LINE_RESET_TOKEN\n");
      print3DcolorVertex(size, &count, buffer);
      print3DcolorVertex(size, &count, buffer);
    }
  }
}

void display(void)
{
  GLfloat feedBuffer[1024];
  GLint size;

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(0.0, 100.0, 0.0, 100.0, 0.0, 1.0);

  glClearColor(0.0, 0.0, 0.0, 0.0);
  glClear(GL_COLOR_BUFFER_BIT);
  drawGeometry(GL_RENDER);

  glFeedbackBuffer(1024, GL_3D_COLOR, feedBuffer);
  (void)glRenderMode(GL_FEEDBACK);
  drawGeometry(GL_FEEDBACK);

  size = glRenderMode(GL_RENDER);
  printBuffer(size, feedBuffer);
}

/*
 * 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, 100, 100);
  if (!auxInitWindow(argv[0]))
    auxQuit();
  myinit();
  auxMainLoop(display);
  return 0;
}