src/redbook/pickdepth.c

   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  34  * Unpublished-- rights reserved under the copyright laws of the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 <GL/glut.h>
  53
  54 void
  55 myinit(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  */
  68 void
  69 drawRects(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  */
 103 void
 104 processHits(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
 134 void
 135 pickRects(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
 167 void
 168 display(void)
 169 {
 170   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 171   drawRects(GL_RENDER);
 172   glutSwapBuffers();
 173 }
 174
 175 void
 176 myReshape(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
 186 static void
 187 key(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  */
 203 int
 204 main(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 }