bool drawing::worldToScreen(vector_3d wrl, int *x, int *y)
{
  if ( !x || !y )
  {
    return false;
  }

  *x = 0;
  *y = 0;

  /**********************************
  Credits to OGC for world2screen
  **********************************/
  float xy[2] =
  {
    (m_pExport->m_iWidth  >> 1),
    (m_pExport->m_iHeight >> 1)
  };

  if( actual_fov == 0.0  )
  {
    actual_fov = 90;
  }

  if( !actual_vieworg._is_valid()
    || actual_vieworg._is_zero() )
  {
    return false;
  }

  if( !actual_viewang._is_valid()
    || actual_viewang._is_zero() )
  {
    return false;
  }

  vector_3d aim,newaim,view,tmp;

  aim._vector_copy (actual_vieworg - wrl);
  view._make_vector(actual_viewang);

  if ( view._vector_anglesf( aim ) > (actual_fov / 1.8) )
  {
    return false;
  }

  aim._vector_rotate_z(-actual_viewang.y,newaim);
  newaim._vector_rotate_y(-actual_viewang.x,tmp);
  tmp._vector_rotate_x(-actual_viewang.z,newaim);

  if ( newaim.x <= 0 )
  {
    return false;
  }

  float num = ((xy[0] / newaim.x) * (120.0 / actual_fov - 1.0 / 3.0));

  *x = xy[0] - num * newaim.y;
  *y = xy[1] - num * newaim.z;

#define _BOUND_VALUE(var,min,max)                 \
  if((var)>=(max)){return false/*(var)=(max)*/;}; \
  if((var)<=(min)){return false/*(var)=(min)*/;}

  _BOUND_VALUE(*x,0,xy[0]*2);
  _BOUND_VALUE(*y,0,xy[1]*2);

  return true;

}

bool drawing::worldToScreen(vector_3d worldCoord, int *xy)
{
  if ( xy )
  {
    if ( worldToScreen(worldCoord,&xy[0],&xy[1]) )
    {
      return true;
    }
  }
  return false;
}

bool drawing::worldToScreen(vector_3d worldCoord, vector_3d screenCoord)
{
  int xy[2] = {0,0};
  if ( worldToScreen(worldCoord, &xy[0], &xy[1]) )
  {
    screenCoord._init(xy[0],xy[1],0);
    return true;
  }
  return false;
}