www.pudn.com > openglbk.rar > picksquare.c

/* 
 * Copyright (c) 1993-1999, 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 * Unpublished-- rights reserved under the copyright laws of the 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. 
 */ 
 
/* 
 * picksquare.c 
 * Use of multiple names and picking are demonstrated.   
 * A 3x3 grid of squares is drawn.  When the left mouse  
 * button is pressed, all squares under the cursor position  
 * have their color changed. 
 */ 
#include  
#include  
#include  
 
int board[3][3];   /*  amount of color for each square	*/ 
 
/*  Clear color value for every square on the board   */ 
void init(void) 
{ 
   int i, j; 
   for (i = 0; i < 3; i++)  
      for (j = 0; j < 3; j ++) 
         board[i][j] = 0; 
   glClearColor (0.0, 0.0, 0.0, 0.0); 
} 
 
/*  The nine squares are drawn.  In selection mode, each  
 *  square is given two names:  one for the row and the  
 *  other for the column on the grid.  The color of each  
 *  square is determined by its position on the grid, and  
 *  the value in the board[][] array. 
 */ 
void drawSquares(GLenum mode) 
{ 
   GLuint i, j; 
   for (i = 0; i < 3; i++) { 
      if (mode == GL_SELECT) 
         glLoadName (i); 
      for (j = 0; j < 3; j ++) { 
         if (mode == GL_SELECT) 
            glPushName (j); 
         glColor3f ((GLfloat) i/3.0, (GLfloat) j/3.0,  
                    (GLfloat) board[i][j]/3.0); 
         glRecti (i, j, i+1, j+1); 
         if (mode == GL_SELECT) 
            glPopName (); 
      } 
   } 
} 
 
/*  processHits prints out the contents of the  
 *  selection array. 
 */ 
void processHits (GLint hits, GLuint buffer[]) 
{ 
   unsigned int i, j; 
   GLuint ii, jj, 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 this hit = %d\n", names); ptr++; 
      printf("  z1 is %g;", (float) *ptr/0x7fffffff); ptr++; 
      printf(" z2 is %g\n", (float) *ptr/0x7fffffff); ptr++; 
      printf ("   names are "); 
      for (j = 0; j < names; j++) { /*  for each name */ 
         printf ("%d ", *ptr); 
         if (j == 0)  /*  set row and column  */ 
            ii = *ptr; 
         else if (j == 1) 
            jj = *ptr; 
         ptr++; 
      } 
      printf ("\n"); 
      board[ii][jj] = (board[ii][jj] + 1) % 3; 
   } 
} 
 
/*  pickSquares() sets up selection mode, name stack,  
 *  and projection matrix for picking.  Then the  
 *  objects are drawn. 
 */ 
#define BUFSIZE 512 
 
void pickSquares(int button, int state, int x, int y) 
{ 
   GLuint selectBuf[BUFSIZE]; 
   GLint hits; 
   GLint viewport[4]; 
 
   if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN) 
      return; 
 
   glGetIntegerv (GL_VIEWPORT, viewport); 
 
   glSelectBuffer (BUFSIZE, selectBuf); 
   (void) glRenderMode (GL_SELECT); 
 
   glInitNames(); 
   glPushName(0); 
 
   glMatrixMode (GL_PROJECTION); 
   glPushMatrix (); 
   glLoadIdentity (); 
/*  create 5x5 pixel picking region near cursor location	*/ 
   gluPickMatrix ((GLdouble) x, (GLdouble) (viewport[3] - y),  
                  5.0, 5.0, viewport); 
   gluOrtho2D (0.0, 3.0, 0.0, 3.0); 
   drawSquares (GL_SELECT); 
 
   glMatrixMode (GL_PROJECTION); 
   glPopMatrix (); 
   glFlush (); 
 
   hits = glRenderMode (GL_RENDER); 
   processHits (hits, selectBuf); 
   glutPostRedisplay(); 
}  
 
void display(void) 
{ 
   glClear(GL_COLOR_BUFFER_BIT); 
   drawSquares (GL_RENDER); 
   glFlush(); 
} 
 
void reshape(int w, int h) 
{ 
   glViewport(0, 0, w, h); 
   glMatrixMode(GL_PROJECTION); 
   glLoadIdentity(); 
   gluOrtho2D (0.0, 3.0, 0.0, 3.0); 
   glMatrixMode(GL_MODELVIEW); 
   glLoadIdentity(); 
} 
 
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); 
   glutInitWindowSize (100, 100); 
   glutInitWindowPosition (100, 100); 
   glutCreateWindow (argv[0]); 
   init (); 
   glutReshapeFunc (reshape); 
   glutDisplayFunc(display);  
   glutMouseFunc (pickSquares); 
   glutKeyboardFunc (keyboard); 
   glutMainLoop(); 
   return 0;  
}