www.pudn.com > openglbk.rar > feedback.c

/* 
 * Copyright (c) 1993-1999, 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 * Unpublished-- rights reserved under the copyright laws of the 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. 
 */ 
 
/* 
 * 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  
#include  
#include  
 
/*  Initialize lighting. 
 */ 
void init(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); 
} 
 
void keyboard(unsigned char key, int x, int y) 
{ 
   switch (key) { 
      case 27: 
         exit(0); 
         break; 
   } 
} 
 
/*  Main Loop  */ 
int main(int argc, char** argv) 
{ 
   glutInit(&argc, argv); 
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); 
   glutInitWindowSize (100, 100); 
   glutInitWindowPosition (100, 100); 
   glutCreateWindow(argv[0]); 
   init(); 
   glutDisplayFunc(display); 
   glutKeyboardFunc (keyboard); 
   glutMainLoop(); 
   return 0;  
}