$Metalregion

Setting the regions of metal. Here the 100% reflection are set in the metal region

$Metalregion
Nregion
$x_l$, $x_R$, $y_{bottom}$, $y_{top}$
$x_l$, $x_R$, $y_{bottom}$, $y_{top}$
...
...
...
$x_l$, $x_R$, $y_{bottom}$, $y_{top}$