code: public static Point tileToScreen (
          MisoSceneMetrics metrics, int x, int y, Point spos)
      {
          spos.x = (x - y - 1) * metrics.tilehwid;
          spos.y = (x + y) * metrics.tilehhei;
          return spos;
      }
docs: Convert the given tile-based coordinates to their corresponding
  screen-based pixel coordinates. The screen coordinate for a tile is
  the upper-left coordinate of the rectangle that bounds the tile
  polygon. Converted coordinates are placed in the given point
  object.
  
  @param x the tile x-position coordinate.
  @param y the tile y-position coordinate.
  @param spos the point object to place coordinates in.
  
  @return the point instance supplied via the <code>spos</code>
  parameter.