progs/redbook/picksquare.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  31  * Unpublished-- rights reserved under the copyright laws of the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  * picksquare.c
  40  * Use of multiple names and picking are demonstrated.
  41  * A 3x3 grid of squares is drawn.  When the left mouse
  42  * button is pressed, all squares under the cursor position
  43  * have their color changed.
  44  */
  45 #include <stdlib.h>
  46 #include <stdio.h>
  47 #include <GL/glut.h>
  48
  49 int board[3][3];   /*  amount of color for each square  */
  50
  51 /*  Clear color value for every square on the board   */
  52 static void init(void)
  53 {
  54    int i, j;
  55    for (i = 0; i < 3; i++)
  56       for (j = 0; j < 3; j ++)
  57          board[i][j] = 0;
  58    glClearColor (0.0, 0.0, 0.0, 0.0);
  59 }
  60
  61 /*  The nine squares are drawn.  In selection mode, each
  62  *  square is given two names:  one for the row and the
  63  *  other for the column on the grid.  The color of each
  64  *  square is determined by its position on the grid, and
  65  *  the value in the board[][] array.
  66  */
  67 static void drawSquares(GLenum mode)
  68 {
  69    GLuint i, j;
  70    for (i = 0; i < 3; i++) {
  71       if (mode == GL_SELECT)
  72          glLoadName (i);
  73       for (j = 0; j < 3; j ++) {
  74          if (mode == GL_SELECT)
  75             glPushName (j);
  76          glColor3f ((GLfloat) i/3.0, (GLfloat) j/3.0,
  77                     (GLfloat) board[i][j]/3.0);
  78          glRecti (i, j, i+1, j+1);
  79          if (mode == GL_SELECT)
  80             glPopName ();
  81       }
  82    }
  83 }
  84
  85 /*  processHits prints out the contents of the
  86  *  selection array.
  87  */
  88 static void processHits (GLint hits, GLuint buffer[])
  89 {
  90    GLint i;
  91    GLuint j, ii = 0, jj = 0, names, *ptr;
  92
  93    printf ("hits = %d\n", hits);
  94    ptr = (GLuint *) buffer;
  95    for (i = 0; i < hits; i++) { /*  for each hit  */
  96       names = *ptr;
  97       printf (" number of names for this hit = %d\n", names); ptr++;
  98       printf("  z1 is %g;", (float) *ptr/0x7fffffff); ptr++;
  99       printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++;
 100       printf ("   names are ");
 101       for (j = 0; j < names; j++) { /*  for each name */
 102          printf ("%d ", *ptr);
 103          if (j == 0)  /*  set row and column  */
 104             ii = *ptr;
 105          else if (j == 1)
 106             jj = *ptr;
 107          ptr++;
 108       }
 109       printf ("\n");
 110       board[ii][jj] = (board[ii][jj] + 1) % 3;
 111    }
 112 }
 113
 114 /*  pickSquares() sets up selection mode, name stack,
 115  *  and projection matrix for picking.  Then the
 116  *  objects are drawn.
 117  */
 118 #define BUFSIZE 512
 119
 120 static void pickSquares(int button, int state, int x, int y)
 121 {
 122    GLuint selectBuf[BUFSIZE];
 123    GLint hits;
 124    GLint viewport[4];
 125
 126    if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN)
 127       return;
 128
 129    glGetIntegerv (GL_VIEWPORT, viewport);
 130
 131    glSelectBuffer (BUFSIZE, selectBuf);
 132    (void) glRenderMode (GL_SELECT);
 133
 134    glInitNames();
 135    glPushName(0);
 136
 137    glMatrixMode (GL_PROJECTION);
 138    glPushMatrix ();
 139    glLoadIdentity ();
 140 /*  create 5x5 pixel picking region near cursor location        */
 141    gluPickMatrix ((GLdouble) x, (GLdouble) (viewport[3] - y),
 142                   5.0, 5.0, viewport);
 143    gluOrtho2D (0.0, 3.0, 0.0, 3.0);
 144    drawSquares (GL_SELECT);
 145
 146    glMatrixMode (GL_PROJECTION);
 147    glPopMatrix ();
 148    glFlush ();
 149
 150    hits = glRenderMode (GL_RENDER);
 151    processHits (hits, selectBuf);
 152    glutPostRedisplay();
 153 }
 154
 155 static void display(void)
 156 {
 157    glClear(GL_COLOR_BUFFER_BIT);
 158    drawSquares (GL_RENDER);
 159    glFlush();
 160 }
 161
 162 static void reshape(int w, int h)
 163 {
 164    glViewport(0, 0, w, h);
 165    glMatrixMode(GL_PROJECTION);
 166    glLoadIdentity();
 167    gluOrtho2D (0.0, 3.0, 0.0, 3.0);
 168    glMatrixMode(GL_MODELVIEW);
 169    glLoadIdentity();
 170 }
 171
 172 /* ARGSUSED1 */
 173 static void keyboard(unsigned char key, int x, int y)
 174 {
 175    switch (key) {
 176       case 27:
 177          exit(0);
 178          break;
 179    }
 180 }
 181
 182 /* Main Loop */
 183 int main(int argc, char** argv)
 184 {
 185    glutInit(&argc, argv);
 186    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
 187    glutInitWindowSize (100, 100);
 188    glutInitWindowPosition (100, 100);
 189    glutCreateWindow (argv[0]);
 190    init ();
 191    glutReshapeFunc (reshape);
 192    glutDisplayFunc(display);
 193    glutMouseFunc (pickSquares);
 194    glutKeyboardFunc (keyboard);
 195    glutMainLoop();
 196    return 0;
 197 }