Linen curtain with eyelets for skylights.
The scene contains a simplified model of a window in the wall at an angle.

For Corona render, it is recommended to install version no lower than 1.5, since the glossiness of the materials is adjusted taking into account PBR.

If you are working in a V-Ray version lower than 3.1, then be careful, in the materials in the BRDF section there is Microfaset GTR (GGX), if your version is older, then the BRDF field will be empty. Choose Blinn, Phong or Ward - whichever is preferable for you.