Linen curtains with dark edging
Transparency can be changed by the opacity map value.
Curtains in zara home style

The Turbosmooth modifier is applied to the curtains and enabled for rendering.
(If errors occur, remove the modifier and reapply)

Corona version 10
CoronaLegacyMtl Materials
In CoronaRender 6 and below CoronaLegacyMtl=CoronaMtl
CoronaLegacyMtl requires Corona Renderer version 1.5 or higher