PICKDPTH.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  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 "glos.h" 
 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include <GL/glaux.h> 
#include <stdio.h> 
 
void myinit(void); 
void drawRects(GLenum mode); 
void processHits (GLint hits, GLuint buffer[]); 
void CALLBACK pickRects(AUX_EVENTREC *event); 
void CALLBACK display(void); 
void CALLBACK myReshape(GLsizei w, GLsizei h); 
 
void myinit(void) 
{ 
    glClearColor (0.0, 0.0, 0.0, 0.0); 
    glDepthFunc(GL_LESS); 
    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); 
    glColor3f (0.0, 1.0, 1.0); 
    glVertex3i (3, 2, -1); 
    glVertex3i (3, 8, -1); 
    glVertex3i (8, 8, -1); 
    glVertex3i (8, 2, -1); 
    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[]) 
{ 
    int i; 
    GLint 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 %u;", *ptr); ptr++; 
        //printf (" z2 is %u\n", *ptr); ptr++; 
        //printf ("   the name is "); 
/* 
        for (j = 0; j < names; j++) { 
            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 CALLBACK pickRects(AUX_EVENTREC *event) 
{ 
    GLuint selectBuf[BUFSIZE]; 
    GLint hits; 
    GLint viewport[4]; 
    int x, y; 
 
    x = event->data[AUX_MOUSEX]; 
    y = event->data[AUX_MOUSEY]; 
    glGetIntegerv (GL_VIEWPORT, viewport); 
 
    glSelectBuffer (BUFSIZE, selectBuf); 
    (void) glRenderMode (GL_SELECT); 
 
    glInitNames(); 
    glPushName((unsigned)-1); 
 
    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 CALLBACK display(void) 
{ 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    drawRects (GL_RENDER); 
    glFlush(); 
} 
 
void CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    glViewport(0, 0, w, h); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    glOrtho (0.0, 8.0, 0.0, 8.0, 0.0, 2.0); 
    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
} 
 
/*  Main Loop 
 *  Open window with initial window size, title bar,  
 *  RGBA display mode, depth buffer, and handle input events. 
 */ 
int main(int argc, char** argv) 
{ 
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB | AUX_DEPTH16); 
    auxInitPosition (0, 0, 100, 100); 
    auxInitWindow ("Picking Rectangles"); 
    myinit (); 
    auxMouseFunc (AUX_LEFTBUTTON, AUX_MOUSEDOWN, pickRects); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}