Amiga MA Magazine 1998 #6/amigamamagazinepolishissue1998.iso/coders/mesa-1.2.8/book/pickdepth.c

C/C++ Source or Header | 1996-05-27 | 6KB | 181 lines

/*
 * (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 * Unpublished-- rights reserved under the copyright laws of the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.
 */
/*
 *  pickdepth.c
 *  Picking is demonstrated in this program.  In
 *  rendering mode, three overlapping rectangles are
 *  drawn.  When the left mouse button is pressed,
 *  selection mode is entered with the picking matrix.
 *  Rectangles which are drawn under the cursor position
 *  are "picked."  Pay special attention to the depth
 *  value range, which is returned.
 */
#include <GL/gl.h>
#include <GL/glu.h>
#include <stdio.h>
#include <stdlib.h>
#include "glaux.h"

void myinit(void)
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_FLAT);
    glDepthRange (0.0, 1.0);    /*  The default z mapping    */
}

/*  The three rectangles are drawn.  In selection mode,
 *  each rectangle is given the same name.  Note that
 *  each rectangle is drawn with a different z value.
 */
void drawRects(GLenum mode)
{
    if (mode == GL_SELECT)
    glLoadName (1);
    glBegin (GL_QUADS);
    glColor3f (1.0, 1.0, 0.0);
    glVertex3i (2, 0, 0);
    glVertex3i (2, 6, 0);
    glVertex3i (6, 6, 0);
    glVertex3i (6, 0, 0);
    glColor3f (0.0, 1.0, 1.0);
    glVertex3i (3, 2, -1);
    glVertex3i (3, 8, -1);
    glVertex3i (8, 8, -1);
    glVertex3i (8, 2, -1);
    glColor3f (1.0, 0.0, 1.0);
    glVertex3i (0, 2, -2);
    glVertex3i (0, 7, -2);
    glVertex3i (5, 7, -2);
    glVertex3i (5, 2, -2);
    glEnd ();
}

/*  processHits() prints out the contents of the
 *  selection array.
 */
void processHits (GLint hits, GLuint buffer[])
{
    unsigned int i, j;
    GLuint names, *ptr;

    printf ("hits = %d\n", hits);
    ptr = (GLuint *) buffer;
    for (i = 0; i < hits; i++) {    /*  for each hit  */
    names = *ptr;
    printf (" number of names for hit = %d\n", names); ptr++;
    printf ("  z1 is %u;", *ptr); ptr++;
    printf (" z2 is %u\n", *ptr); ptr++;
    printf ("   the name is ");
    for (j = 0; j < names; j++) {    /*  for each name */
        printf ("%d ", *ptr); ptr++;
    }
    printf ("\n");
    }
}

/*  pickRects() sets up selection mode, name stack,
 *  and projection matrix for picking.  Then the objects
 *  are drawn.
 */
#define BUFSIZE 512

void pickRects(AUX_EVENTREC *event)
{
    GLuint selectBuf[BUFSIZE];
    GLint hits;
    GLint viewport[4];
    int x, y;

    x = event->data[AUX_MOUSEX];
    y = event->data[AUX_MOUSEY];
    glGetIntegerv (GL_VIEWPORT, viewport);

    glSelectBuffer (BUFSIZE, selectBuf);
    (void) glRenderMode (GL_SELECT);

    glInitNames();
    glPushName(-1);

    glMatrixMode (GL_PROJECTION);
    glPushMatrix ();
    glLoadIdentity ();
/*  create 5x5 pixel picking region near cursor location    */
    gluPickMatrix ((GLdouble) x, (GLdouble) (viewport[3] - y),
    5.0, 5.0, viewport);
    glOrtho (0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
    drawRects (GL_SELECT);
    glPopMatrix ();
    glFlush ();

    hits = glRenderMode (GL_RENDER);
    processHits (hits, selectBuf);
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    drawRects (GL_RENDER);
    glFlush();
}

void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho (0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

/*  Main Loop
 *  Open window with initial window size, title bar,
 *  RGBA display mode, depth buffer, and handle input events.
 */
int main(int argc, char** argv)
{
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB | AUX_DEPTH);
    auxInitPosition (0, 0, 100, 100);
    auxInitWindow (argv[0]);
    myinit ();
    auxMouseFunc (AUX_LEFTBUTTON, AUX_MOUSEDOWN, pickRects);
    auxReshapeFunc (myReshape);
    auxMainLoop(display);
}