www.pudn.com > openglbk.rar > pickdepth.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 * Unpublished-- rights reserved under the copyright laws of the 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. 
 */ 
 
/* 
 * pickdepth.c 
 * Picking is demonstrated in this program.  In  
 * rendering mode, three overlapping rectangles are  
 * drawn.  When the left mouse button is pressed,  
 * selection mode is entered with the picking matrix.   
 * Rectangles which are drawn under the cursor position 
 * are "picked."  Pay special attention to the depth  
 * value range, which is returned. 
 */ 
#include  
#include  
#include  
 
void init(void) 
{ 
   glClearColor(0.0, 0.0, 0.0, 0.0); 
   glEnable(GL_DEPTH_TEST); 
   glShadeModel(GL_FLAT); 
   glDepthRange(0.0, 1.0);  /* The default z mapping */ 
} 
 
/* The three rectangles are drawn.  In selection mode,  
 * each rectangle is given the same name.  Note that  
 * each rectangle is drawn with a different z value. 
 */ 
void drawRects(GLenum mode) 
{ 
   if (mode == GL_SELECT) 
      glLoadName(1); 
   glBegin(GL_QUADS); 
   glColor3f(1.0, 1.0, 0.0); 
   glVertex3i(2, 0, 0); 
   glVertex3i(2, 6, 0); 
   glVertex3i(6, 6, 0); 
   glVertex3i(6, 0, 0); 
   glEnd(); 
   if (mode == GL_SELECT) 
      glLoadName(2); 
   glBegin(GL_QUADS); 
   glColor3f(0.0, 1.0, 1.0); 
   glVertex3i(3, 2, -1); 
   glVertex3i(3, 8, -1); 
   glVertex3i(8, 8, -1); 
   glVertex3i(8, 2, -1); 
   glEnd(); 
   if (mode == GL_SELECT) 
      glLoadName(3); 
   glBegin(GL_QUADS); 
   glColor3f(1.0, 0.0, 1.0); 
   glVertex3i(0, 2, -2); 
   glVertex3i(0, 7, -2); 
   glVertex3i(5, 7, -2); 
   glVertex3i(5, 2, -2); 
   glEnd(); 
} 
 
/*  processHits() prints out the contents of the  
 *  selection array. 
 */ 
void processHits(GLint hits, GLuint buffer[]) 
{ 
   unsigned int i, j; 
   GLuint 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"); 
   } 
} 
 
/*  pickRects() sets up selection mode, name stack,  
 *  and projection matrix for picking.  Then the objects  
 *  are drawn. 
 */ 
#define BUFSIZE 512 
 
void pickRects(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); 
   glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5); 
   drawRects(GL_SELECT); 
   glPopMatrix(); 
   glFlush(); 
 
   hits = glRenderMode(GL_RENDER); 
   processHits(hits, selectBuf); 
} 
 
void display(void) 
{ 
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
   drawRects(GL_RENDER); 
   glFlush(); 
} 
 
void reshape(int w, int h) 
{ 
   glViewport(0, 0, (GLsizei) w, (GLsizei) h); 
   glMatrixMode(GL_PROJECTION); 
   glLoadIdentity(); 
   glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5); 
   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 | GLUT_DEPTH); 
   glutInitWindowSize (200, 200); 
   glutInitWindowPosition (100, 100); 
   glutCreateWindow(argv[0]); 
   init(); 
   glutReshapeFunc(reshape); 
   glutDisplayFunc(display); 
   glutMouseFunc(pickRects); 
   glutKeyboardFunc(keyboard); 
   glutMainLoop(); 
   return 0;  
}