pickdepth.c revision 32001f49 
1
2/* Copyright (c) Mark J. Kilgard, 1994. */
3
4/*
5 * (c) Copyright 1993, Silicon Graphics, Inc.
6 * ALL RIGHTS RESERVED
7 * Permission to use, copy, modify, and distribute this software for
8 * any purpose and without fee is hereby granted, provided that the above
9 * copyright notice appear in all copies and that both the copyright notice
10 * and this permission notice appear in supporting documentation, and that
11 * the name of Silicon Graphics, Inc. not be used in advertising
12 * or publicity pertaining to distribution of the software without specific,
13 * written prior permission.
14 *
15 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
16 * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
17 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
18 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
19 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
20 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
21 * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
22 * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
23 * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
24 * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
25 * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
26 * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
27 *
28 * US Government Users Restricted Rights
29 * Use, duplication, or disclosure by the Government is subject to
30 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
31 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
32 * clause at DFARS 252.227-7013 and/or in similar or successor
33 * clauses in the FAR or the DOD or NASA FAR Supplement.
34 * Unpublished-- rights reserved under the copyright laws of the
35 * United States.  Contractor/manufacturer is Silicon Graphics,
36 * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
37 *
38 * OpenGL(TM) is a trademark of Silicon Graphics, Inc.
39 */
40/*
41 *  pickdepth.c
42 *  Picking is demonstrated in this program.  In
43 *  rendering mode, three overlapping rectangles are
44 *  drawn.  When the left mouse button is pressed,
45 *  selection mode is entered with the picking matrix.
46 *  Rectangles which are drawn under the cursor position
47 *  are "picked."  Pay special attention to the depth
48 *  value range, which is returned.
49 */
50#include <stdlib.h>
51#include <stdio.h>
52#include "glut_wrap.h"
53
54static void
55myinit(void)
56{
57  glClearColor(0.0, 0.0, 0.0, 0.0);
58  glDepthFunc(GL_LESS);
59  glEnable(GL_DEPTH_TEST);
60  glShadeModel(GL_FLAT);
61  glDepthRange(0.0, 1.0);  /* The default z mapping */
62}
63
64/*  The three rectangles are drawn.  In selection mode,
65 *  each rectangle is given the same name.  Note that
66 *  each rectangle is drawn with a different z value.
67 */
68static void
69drawRects(GLenum mode)
70{
71  if (mode == GL_SELECT)
72    glLoadName(1);
73  glBegin(GL_QUADS);
74  glColor3f(1.0, 1.0, 0.0);
75  glVertex3i(2, 0, 0);
76  glVertex3i(2, 6, 0);
77  glVertex3i(6, 6, 0);
78  glVertex3i(6, 0, 0);
79  glEnd();
80  if (mode == GL_SELECT)
81    glLoadName(2);
82  glBegin(GL_QUADS);
83  glColor3f(0.0, 1.0, 1.0);
84  glVertex3i(3, 2, -1);
85  glVertex3i(3, 8, -1);
86  glVertex3i(8, 8, -1);
87  glVertex3i(8, 2, -1);
88  glEnd();
89  if (mode == GL_SELECT)
90    glLoadName(3);
91  glBegin(GL_QUADS);
92  glColor3f(1.0, 0.0, 1.0);
93  glVertex3i(0, 2, -2);
94  glVertex3i(0, 7, -2);
95  glVertex3i(5, 7, -2);
96  glVertex3i(5, 2, -2);
97  glEnd();
98}
99
100/*  processHits() prints out the contents of the
101 *  selection array.
102 */
103static void
104processHits(GLint hits, GLuint buffer[])
105{
106  GLint i;
107  GLuint j, names, *ptr;
108
109  printf("hits = %d\n", hits);
110  ptr = (GLuint *) buffer;
111  for (i = 0; i < hits; i++) {  /* for each hit  */
112    names = *ptr;
113    printf(" number of names for hit = %d\n", names);
114    ptr++;
115    printf("  z1 is %g;", (float) *ptr/0xffffffff);
116    ptr++;
117    printf(" z2 is %g\n", (float) *ptr/0xffffffff);
118    ptr++;
119    printf("   the name is ");
120    for (j = 0; j < names; j++) {  /* for each name */
121      printf("%d ", *ptr);
122      ptr++;
123    }
124    printf("\n");
125  }
126}
127
128/*  pickRects() sets up selection mode, name stack,
129 *  and projection matrix for picking.  Then the objects
130 *  are drawn.
131 */
132#define BUFSIZE 512
133
134static void
135pickRects(int button, int state, int x, int y)
136{
137  GLuint selectBuf[BUFSIZE];
138  GLint hits;
139  GLint viewport[4];
140
141  if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN)
142    return;
143
144  glGetIntegerv(GL_VIEWPORT, viewport);
145
146  glSelectBuffer(BUFSIZE, selectBuf);
147  (void) glRenderMode(GL_SELECT);
148
149  glInitNames();
150  glPushName(-1);
151
152  glMatrixMode(GL_PROJECTION);
153  glPushMatrix();
154  glLoadIdentity();
155/*  create 5x5 pixel picking region near cursor location */
156  gluPickMatrix((GLdouble) x, (GLdouble) (viewport[3] - y),
157    5.0, 5.0, viewport);
158  glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
159  drawRects(GL_SELECT);
160  glPopMatrix();
161  glFlush();
162
163  hits = glRenderMode(GL_RENDER);
164  processHits(hits, selectBuf);
165}
166
167static void
168display(void)
169{
170  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
171  drawRects(GL_RENDER);
172  glutSwapBuffers();
173}
174
175static void
176myReshape(int w, int h)
177{
178  glViewport(0, 0, w, h);
179  glMatrixMode(GL_PROJECTION);
180  glLoadIdentity();
181  glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
182  glMatrixMode(GL_MODELVIEW);
183  glLoadIdentity();
184}
185
186static void
187key(unsigned char k, int x, int y)
188{
189  switch (k) {
190  case 27:  /* Escape */
191    exit(0);
192    break;
193  default:
194    return;
195  }
196  glutPostRedisplay();
197}
198
199/*  Main Loop
200 *  Open window with initial window size, title bar,
201 *  RGBA display mode, depth buffer, and handle input events.
202 */
203int
204main(int argc, char **argv)
205{
206  glutInitWindowSize(200, 200);
207  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
208  glutInit(&argc, argv);
209  glutCreateWindow(argv[0]);
210  myinit();
211  glutMouseFunc(pickRects);
212  glutReshapeFunc(myReshape);
213  glutDisplayFunc(display);
214  glutKeyboardFunc(key);
215  glutMainLoop();
216  return 0;             /* ANSI C requires main to return int. */
217}
218