summaryrefslogtreecommitdiff
path: root/progs/redbook/select.c
blob: 537d5194d46ae20704b42bb8f07e98a63ac27311 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
/*
 * Copyright (c) 1993-1997, 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.
 */

/*
 * select.c
 * This is an illustration of the selection mode and 
 * name stack, which detects whether objects which collide 
 * with a viewing volume.  First, four triangles and a 
 * rectangular box representing a viewing volume are drawn 
 * (drawScene routine).  The green triangle and yellow 
 * triangles appear to lie within the viewing volume, but 
 * the red triangle appears to lie outside it.  Then the 
 * selection mode is entered (selectObjects routine).  
 * Drawing to the screen ceases.  To see if any collisions 
 * occur, the four triangles are called.  In this example, 
 * the green triangle causes one hit with the name 1, and 
 * the yellow triangles cause one hit with the name 3.
 */
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

/* draw a triangle with vertices at (x1, y1), (x2, y2) 
 * and (x3, y3) at z units away from the origin.
 */
static void drawTriangle (GLfloat x1, GLfloat y1, GLfloat x2, 
    GLfloat y2, GLfloat x3, GLfloat y3, GLfloat z)
{
   glBegin (GL_TRIANGLES);
   glVertex3f (x1, y1, z);
   glVertex3f (x2, y2, z);
   glVertex3f (x3, y3, z);
   glEnd ();
}

/* draw a rectangular box with these outer x, y, and z values */
static void drawViewVolume (GLfloat x1, GLfloat x2, GLfloat y1, 
                            GLfloat y2, GLfloat z1, GLfloat z2)
{
   glColor3f (1.0, 1.0, 1.0);
   glBegin (GL_LINE_LOOP);
   glVertex3f (x1, y1, -z1);
   glVertex3f (x2, y1, -z1);
   glVertex3f (x2, y2, -z1);
   glVertex3f (x1, y2, -z1);
   glEnd ();

   glBegin (GL_LINE_LOOP);
   glVertex3f (x1, y1, -z2);
   glVertex3f (x2, y1, -z2);
   glVertex3f (x2, y2, -z2);
   glVertex3f (x1, y2, -z2);
   glEnd ();

   glBegin (GL_LINES);	/*  4 lines	*/
   glVertex3f (x1, y1, -z1);
   glVertex3f (x1, y1, -z2);
   glVertex3f (x1, y2, -z1);
   glVertex3f (x1, y2, -z2);
   glVertex3f (x2, y1, -z1);
   glVertex3f (x2, y1, -z2);
   glVertex3f (x2, y2, -z1);
   glVertex3f (x2, y2, -z2);
   glEnd ();
}

/* drawScene draws 4 triangles and a wire frame
 * which represents the viewing volume.
 */
static void drawScene (void)
{
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   gluPerspective (40.0, 4.0/3.0, 1.0, 100.0);

   glMatrixMode (GL_MODELVIEW);
   glLoadIdentity ();
   gluLookAt (7.5, 7.5, 12.5, 2.5, 2.5, -5.0, 0.0, 1.0, 0.0);
   glColor3f (0.0, 1.0, 0.0);	/*  green triangle	*/
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
   glColor3f (1.0, 0.0, 0.0);	/*  red triangle	*/
   drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
   glColor3f (1.0, 1.0, 0.0);	/*  yellow triangles	*/
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
   drawViewVolume (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
}

/* processHits prints out the contents of the selection array
 */
static void processHits (GLint hits, GLuint buffer[])
{
   GLint i;
   GLuint j, 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 %g;", (float) *ptr/0x7fffffff); ptr++;
      printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++;
      printf ("   the name is ");
      for (j = 0; j < names; j++) {	/*  for each name */
         printf ("%d ", *ptr); ptr++;
      }
      printf ("\n");
   }
}

/* selectObjects "draws" the triangles in selection mode, 
 * assigning names for the triangles.  Note that the third
 * and fourth triangles share one name, so that if either 
 * or both triangles intersects the viewing/clipping volume, 
 * only one hit will be registered.
 */
#define BUFSIZE 512

static void selectObjects(void)
{
   GLuint selectBuf[BUFSIZE];
   GLint hits;

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

   glInitNames();
   glPushName(0);

   glPushMatrix ();
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();
   glOrtho (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
   glMatrixMode (GL_MODELVIEW);
   glLoadIdentity ();
   glLoadName(1);
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
   glLoadName(2);
   drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
   glLoadName(3);
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
   drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
   glPopMatrix ();
   glFlush ();

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

static void init (void) 
{
   glEnable(GL_DEPTH_TEST);
   glShadeModel(GL_FLAT);
}

static void display(void)
{
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   drawScene ();
   selectObjects ();
   glFlush();
}

/* ARGSUSED1 */
static 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 | GLUT_DEPTH);
   glutInitWindowSize (200, 200);
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   init();
   glutDisplayFunc(display);
   glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0; 
}