opengl 질문입니다

void GLWidget::mouseDoubleClickEvent(QMouseEvent *event)
{
    int face = faceAtPosition(event->pos());
    qDebug() << "mouse pos :" << event->pos();
 
    qDebug() << "face :" << face;
        if (face != -1) {
            QColor color = QColorDialog::getColor(faceColors, this);
 
            if (color.isValid()) {
 
                faceColors = color;
                colours[selectedObj] = faceColors;
 
                updateGL();
            }
        }
 
 
 
    qDebug() << "double click";
}

int GLWidget::faceAtPosition(const QPoint &pos)
{
    qDebug() << "faceatpostion" ;
 
    const int MaxSize = 512;
    GLuint buffer[512];
    GLint viewport[4];
 
        makeCurrent();
 
        glGetIntegerv(GL_VIEWPORT, viewport);
       // glPushAttrib(GL_ALL_ATTRIB_BITS);
 
        glSelectBuffer(MaxSize, buffer);
        glRenderMode(GL_SELECT);
 
 
        glInitNames();
 
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        gluPickMatrix(GLdouble(pos.x()), GLdouble(viewport[3] - pos.y()),
                      5.0, 5.0, viewport);
        glOrtho(-3000.0, 3000.0, -3000.0, 3000.0, -30000.0, 30000.0);
 
 
        GLfloat x = ww / hh;
 
        if(isloaded){
            glMatrixMode(GL_MODELVIEW);
 
            drawMarkers();
 
        }
            glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glFlush();
 
 
        if (!glRenderMode(GL_RENDER)){
            qDebug() <<"return";
            return -1;
 
        }
 
        ProcessSelect(buffer);
 
        return buffer[3];
 
 
}

void GLWidget::ProcessSelect(GLuint index[512])
{
    selectedObj=index[3];
 
    qDebug() << "index[3]" << index[3];
    updateGL();
 
  switch(index[3]) {
    case 0: qDebug() << "0 click"; break;
    case 1: qDebug() << "1 click"; break;
    case 2: qDebug() << "2 click"; break;
    case 3: qDebug() << "3 click"; break;
      case 4: qDebug() << "4 click"; break;
      case 5: qDebug() << "5 click"; break;
      case 6: qDebug() << "6 click"; break;
      case 7: qDebug() << "7 click"; break;
      case 8: qDebug() << "8 click"; break;
      case 9: qDebug() << "9 click"; break;
      case 10: qDebug() << "10 click"; break;
      case 11: qDebug() << "11 click"; break;
      case 12: qDebug() << "12 click"; break;
      case 13: qDebug() << "13 click"; break;
      case 14: qDebug() << "14 click"; break;
      case 15: qDebug() << "15 click"; break;
 
      case 100: qDebug() << "100 click"; break;
 
 
 
      default: qDebug() << "what?"; break;
  }
}