newmtl Glass
illum 1
Ka 0.0 0.0 0.0
Kd 0.5019608 0.49803922 0.49803922
Ks 0.0 0.0 0.0
Ns 1.0
Ni 1.0
d 0.9 <---- opaque


newmtl Glass
illum 1
Ka 0.0 0.0 0.0
Kd 0.5019608 0.49803922 0.49803922
Ks 0.0 0.0 0.0
Ns 1.0
Ni 1.0
d 0.2 <---- transparent