progs/redbook/select.c

   1 /*
   2  * Copyright (c) 1993-1997, Silicon Graphics, Inc.
   3  * ALL RIGHTS RESERVED
   4  * Permission to use, copy, modify, and distribute this software for
   5  * any purpose and without fee is hereby granted, provided that the above
   6  * copyright notice appear in all copies and that both the copyright notice
   7  * and this permission notice appear in supporting documentation, and that
   8  * the name of Silicon Graphics, Inc. not be used in advertising
   9  * or publicity pertaining to distribution of the software without specific,
  10  * written prior permission.
  11  *
  12  * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS"
  13  * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
  14  * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
  15  * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
  16  * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
  17  * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY
  18  * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION,
  19  * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF
  20  * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN
  21  * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON
  22  * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE
  23  * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE.
  24  *
  25  * US Government Users Restricted Rights
  26  * Use, duplication, or disclosure by the Government is subject to
  27  * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
  28  * (c)(1)(ii) of the Rights in Technical Data and Computer Software
  29  * clause at DFARS 252.227-7013 and/or in similar or successor
  30  * clauses in the FAR or the DOD or NASA FAR Supplement.
  31  * Unpublished-- rights reserved under the copyright laws of the
  32  * United States.  Contractor/manufacturer is Silicon Graphics,
  33  * Inc., 2011 N.  Shoreline Blvd., Mountain View, CA 94039-7311.
  34  *
  35  * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
  36  */
  37
  38 /*
  39  * select.c
  40  * This is an illustration of the selection mode and
  41  * name stack, which detects whether objects which collide
  42  * with a viewing volume.  First, four triangles and a
  43  * rectangular box representing a viewing volume are drawn
  44  * (drawScene routine).  The green triangle and yellow
  45  * triangles appear to lie within the viewing volume, but
  46  * the red triangle appears to lie outside it.  Then the
  47  * selection mode is entered (selectObjects routine).
  48  * Drawing to the screen ceases.  To see if any collisions
  49  * occur, the four triangles are called.  In this example,
  50  * the green triangle causes one hit with the name 1, and
  51  * the yellow triangles cause one hit with the name 3.
  52  */
  53 #include <GL/glut.h>
  54 #include <stdlib.h>
  55 #include <stdio.h>
  56
  57 /* draw a triangle with vertices at (x1, y1), (x2, y2)
  58  * and (x3, y3) at z units away from the origin.
  59  */
  60 static void drawTriangle (GLfloat x1, GLfloat y1, GLfloat x2,
  61     GLfloat y2, GLfloat x3, GLfloat y3, GLfloat z)
  62 {
  63    glBegin (GL_TRIANGLES);
  64    glVertex3f (x1, y1, z);
  65    glVertex3f (x2, y2, z);
  66    glVertex3f (x3, y3, z);
  67    glEnd ();
  68 }
  69
  70 /* draw a rectangular box with these outer x, y, and z values */
  71 static void drawViewVolume (GLfloat x1, GLfloat x2, GLfloat y1,
  72                             GLfloat y2, GLfloat z1, GLfloat z2)
  73 {
  74    glColor3f (1.0, 1.0, 1.0);
  75    glBegin (GL_LINE_LOOP);
  76    glVertex3f (x1, y1, -z1);
  77    glVertex3f (x2, y1, -z1);
  78    glVertex3f (x2, y2, -z1);
  79    glVertex3f (x1, y2, -z1);
  80    glEnd ();
  81
  82    glBegin (GL_LINE_LOOP);
  83    glVertex3f (x1, y1, -z2);
  84    glVertex3f (x2, y1, -z2);
  85    glVertex3f (x2, y2, -z2);
  86    glVertex3f (x1, y2, -z2);
  87    glEnd ();
  88
  89    glBegin (GL_LINES);  /*  4 lines     */
  90    glVertex3f (x1, y1, -z1);
  91    glVertex3f (x1, y1, -z2);
  92    glVertex3f (x1, y2, -z1);
  93    glVertex3f (x1, y2, -z2);
  94    glVertex3f (x2, y1, -z1);
  95    glVertex3f (x2, y1, -z2);
  96    glVertex3f (x2, y2, -z1);
  97    glVertex3f (x2, y2, -z2);
  98    glEnd ();
  99 }
 100
 101 /* drawScene draws 4 triangles and a wire frame
 102  * which represents the viewing volume.
 103  */
 104 static void drawScene (void)
 105 {
 106    glMatrixMode (GL_PROJECTION);
 107    glLoadIdentity ();
 108    gluPerspective (40.0, 4.0/3.0, 1.0, 100.0);
 109
 110    glMatrixMode (GL_MODELVIEW);
 111    glLoadIdentity ();
 112    gluLookAt (7.5, 7.5, 12.5, 2.5, 2.5, -5.0, 0.0, 1.0, 0.0);
 113    glColor3f (0.0, 1.0, 0.0);   /*  green triangle      */
 114    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
 115    glColor3f (1.0, 0.0, 0.0);   /*  red triangle        */
 116    drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
 117    glColor3f (1.0, 1.0, 0.0);   /*  yellow triangles    */
 118    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
 119    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
 120    drawViewVolume (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
 121 }
 122
 123 /* processHits prints out the contents of the selection array
 124  */
 125 static void processHits (GLint hits, GLuint buffer[])
 126 {
 127    GLint i;
 128    GLuint j, names, *ptr;
 129
 130    printf ("hits = %d\n", hits);
 131    ptr = (GLuint *) buffer;
 132    for (i = 0; i < hits; i++) { /*  for each hit  */
 133       names = *ptr;
 134       printf (" number of names for hit = %d\n", names); ptr++;
 135       printf("  z1 is %g;", (float) *ptr/0x7fffffff); ptr++;
 136       printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++;
 137       printf ("   the name is ");
 138       for (j = 0; j < names; j++) {     /*  for each name */
 139          printf ("%d ", *ptr); ptr++;
 140       }
 141       printf ("\n");
 142    }
 143 }
 144
 145 /* selectObjects "draws" the triangles in selection mode,
 146  * assigning names for the triangles.  Note that the third
 147  * and fourth triangles share one name, so that if either
 148  * or both triangles intersects the viewing/clipping volume,
 149  * only one hit will be registered.
 150  */
 151 #define BUFSIZE 512
 152
 153 static void selectObjects(void)
 154 {
 155    GLuint selectBuf[BUFSIZE];
 156    GLint hits;
 157
 158    glSelectBuffer (BUFSIZE, selectBuf);
 159    (void) glRenderMode (GL_SELECT);
 160
 161    glInitNames();
 162    glPushName(0);
 163
 164    glPushMatrix ();
 165    glMatrixMode (GL_PROJECTION);
 166    glLoadIdentity ();
 167    glOrtho (0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
 168    glMatrixMode (GL_MODELVIEW);
 169    glLoadIdentity ();
 170    glLoadName(1);
 171    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
 172    glLoadName(2);
 173    drawTriangle (2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
 174    glLoadName(3);
 175    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
 176    drawTriangle (2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
 177    glPopMatrix ();
 178    glFlush ();
 179
 180    hits = glRenderMode (GL_RENDER);
 181    processHits (hits, selectBuf);
 182 }
 183
 184 static void init (void)
 185 {
 186    glEnable(GL_DEPTH_TEST);
 187    glShadeModel(GL_FLAT);
 188 }
 189
 190 static void display(void)
 191 {
 192    glClearColor (0.0, 0.0, 0.0, 0.0);
 193    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 194    drawScene ();
 195    selectObjects ();
 196    glFlush();
 197 }
 198
 199 /* ARGSUSED1 */
 200 static void keyboard(unsigned char key, int x, int y)
 201 {
 202    switch (key) {
 203       case 27:
 204          exit(0);
 205          break;
 206    }
 207 }
 208
 209 /*  Main Loop  */
 210 int main(int argc, char** argv)
 211 {
 212    glutInit(&argc, argv);
 213    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
 214    glutInitWindowSize (200, 200);
 215    glutInitWindowPosition (100, 100);
 216    glutCreateWindow (argv[0]);
 217    init();
 218    glutDisplayFunc(display);
 219    glutKeyboardFunc(keyboard);
 220    glutMainLoop();
 221    return 0;
 222 }