gl_pick.cpp

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/* GL selection buffer code
 */

//#include <GL/gl.h>
#include "gl_globals.h"
#include "gfxlib.h"
#include "gl_matrix.h"
#include <GL/glu.h>
#include  <assert.h>
#define SELECTBUF_SIZE MAX_PICK*4
const float     epsilon = 0.001;

static vector< PickData > *picked_objects = new vector< PickData > ();
static unsigned selectbuf[SELECTBUF_SIZE];

using namespace GFXMatrices;

void GFXBeginPick( int x, int y, int xsize, int ysize )
{
    //save and change gl projection matrix
    GLint viewport[4];

    float left, right, bottom, top, fnear, ffar;
    GFXGetFrustumVars( true, &left, &right, &bottom, &top, &fnear, &ffar );

    glMatrixMode( GL_PROJECTION );
    glPushMatrix();
    glLoadIdentity();
    glGetIntegerv( GL_VIEWPORT, viewport );
    gluPickMatrix( x, viewport[3]-y, xsize, ysize, viewport );
    glMultMatrixf( projection );

    glSelectBuffer( SELECTBUF_SIZE, selectbuf );
    glRenderMode( GL_SELECT );
    glGetError();

    delete picked_objects;
    picked_objects = new vector< PickData > ();
}

void GFXSetPickName( int name )
{
    glInitNames();
    glPushName( name );
    glLoadName( name );
    glGetError();
}

void drawRects( GLenum mode )
{
    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();
    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();
    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();
}

//Don't call this function
bool GFXCheckPicked()
{
    assert( 0 );
    glFlush();
    int num_hits = glRenderMode( GL_RENDER );
    glRenderMode( GL_SELECT );
    glGetError();
    assert( num_hits >= 0 && num_hits <= 1 );
    return num_hits > 0;
}

vector< PickData > * GFXEndPick()
{
    int num_hits  = glRenderMode( GL_RENDER );
    assert( num_hits != -1 );
    //num_hits could == -1, check for this case
    unsigned *ptr = selectbuf;
    for (int a = 0; a < num_hits; a++) {
        picked_objects->push_back( PickData( ptr[3], ptr[1], ptr[2] ) );
        ptr += ptr[0]+3;
    }
    //restore gl projection matrix
    glMatrixMode( GL_PROJECTION );
    glPopMatrix();
    return picked_objects;
}