PICKLINE.C

/* 
 * (c) Copyright 1993, Silicon Graphics, Inc. 
 *               1993-1995 Microsoft Corporation 
 * 
 * ALL RIGHTS RESERVED 
 * 
 * Please refer to OpenGL/readme.txt for additional information 
 * 
 */ 
 
/* 
 *  pickline.c 
 *  Picking is demonstrated here.  Press the left mouse button 
 *  is enter picking mode.  You get two hits if you press the 
 *  mouse, while the cursor is where the lines intersect. 
 */ 
#include "glos.h" 
 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include <GL/glaux.h> 
#include <stdio.h> 
 
void myinit(void); 
void drawLine(GLenum mode); 
void CALLBACK pickLine(AUX_EVENTREC *event); 
void CALLBACK display(void); 
void CALLBACK myReshape(GLsizei w, GLsizei h); 
 
void drawLine(GLenum mode) 
{ 
    if (mode == GL_SELECT) 
    glLoadName (1); 
    glBegin (GL_LINES); 
    glColor3f (1.0, 1.0, 1.0); 
    glVertex3f (30.0, 30.0, 0.0); 
    glVertex3f (50.0, 60.0, 0.0); 
    glEnd ();  
 
    if (mode == GL_SELECT) 
    glLoadName (2); 
    glBegin (GL_LINES); 
    glColor3f (1.0, 1.0, 1.0); 
    glVertex3f (50.0, 60.0, 0.0); 
    glVertex3f (70.0, 40.0, 0.0); 
    glEnd ();  
} 
 
/*  pickline() is called when the mouse is pressed. 
 *  The projection matrix is reloaded to include the 
 *  picking matrix.  The line is "redrawn" during 
 *  selection mode, and names are sent to the buffer. 
 */ 
#define BUFSIZE 512 
 
void CALLBACK pickLine(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((GLuint)-1); 
 
    glMatrixMode (GL_PROJECTION); 
    glPushMatrix (); 
    glLoadIdentity (); 
    gluPickMatrix ((GLdouble) x, (GLdouble) (viewport[3] - y),  
    5.0, 5.0, viewport); 
    gluOrtho2D (0.0, (GLdouble) viewport[2],  
    0.0, (GLdouble) viewport[3]); 
    drawLine (GL_SELECT); 
    glPopMatrix (); 
    glFlush (); 
 
    hits = glRenderMode (GL_RENDER); 
    //printf ("hits is %d\n", hits); 
}  
 
void myinit (void)  
{ 
    glShadeModel (GL_FLAT); 
    glClearColor (0.0, 0.0, 0.0, 0.0); 
} 
 
void CALLBACK display(void) 
{ 
    glClear(GL_COLOR_BUFFER_BIT); 
    drawLine (GL_RENDER); 
    glFlush(); 
} 
 
void CALLBACK myReshape(GLsizei w, GLsizei h) 
{ 
    glViewport(0, 0, w, h); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    gluOrtho2D (0.0, (GLdouble) w, 0.0, (GLdouble) h); 
    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
} 
 
/*  Main Loop 
 *  Open window with initial window size, title bar,  
 *  RGBA display mode, and handle input events. 
 */ 
int main(int argc, char** argv) 
{ 
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB); 
    auxInitPosition (0, 0, 100, 100); 
    auxInitWindow ("Picking Lines"); 
    myinit (); 
    auxMouseFunc (AUX_LEFTBUTTON, AUX_MOUSEDOWN, pickLine); 
    auxReshapeFunc (myReshape); 
    auxMainLoop(display); 
    return(0); 
}