$pattern tri region

$pattern_tri_region
pattern_tri_num
$x_1$ $y_1$  $x_2$ $y_2$  $x_3$ $y_3$  $n_r$ $\alpha$ if_empty

For a triangular shape, we need 3 points (x1,y1), (x2,y2), and (x3,y3) to define the triangular shape. Then the refractive index and the absorption coefficient is put in the simulation.