/*
 * (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 * Unpublished-- rights reserved under the copyright laws of the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 "aux.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);
    auxInitWindow (argv[0]);
    myinit ();
    auxMainLoop(display);
}
